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Infection-related preterm birth is a leading cause of infant mortality and morbidity; knowledge of bacterial populations invading the amniotic cavity and the routes of invasion is required to make progress in the prevention of preterm birth. Significant advances have been made in understanding bacterial communities in the vagina, but much less studied are intra-uterine bacterial populations during pregnancy. A systematic review of data published on the intra-uterine microbiome was performed; molecular information and summaries of species found in healthy individuals and in women with diagnosed infections served to construct a database and to analyse results to date. Thirteen studies fulfilled the review's inclusion criteria. The data of various investigations were collated, organized, and re-analyzed to achieve a more comprehensive understanding of microbial populations in the intra-amniotic space. The most common intra-amniotic bacterial taxa were species that can colonies the vagina in health and disease; there were others associated with the habitats of the mouth, gastrointestinal tract, and respiratory tract. The results suggest a central role for the ascending route of infections during pregnancy, and point to a possible secondary contribution via haematogenous invasion of the intra-amniotic space. The complete census of the intra-uterine microbiome awaits completion.
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published: 16 October 2013
doi: 10.3389/fcimb.2013.00058
Bacterial aetiological agents of intra-amniotic infections
and preterm birth in pregnant women
George L. Mendz1*, Nadeem O. Kaakoush2and Julie A. Quinlivan3
1School of Medicine, Sydney, The University of Notre Dame Australia, Darlinghurst, NSW, Australia
2School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Kensington, NSW, Australia
3School of Medicine, Fremantle, The University of Notre Dame Australia, Fremantle, WA, Australia
Edited by:
Paul De Figueiredo, Texas A&M
University, USA
Reviewed by:
Qing-Ming Qin, Jilin University,
Neetu Singh, Texas A&M University,
George L. Mendz, School of
Medicine, Sydney, The University of
Notre Dame Australia, 160 Oxford
St., Darlinghurst, NSW 2010,
Infection-related preterm birth is a leading cause of infant mortality and morbidity;
knowledge of bacterial populations invading the amniotic cavity and the routes of invasion
is required to make progress in the prevention of preterm birth. Significant advances
have been made in understanding bacterial communities in the vagina, but much less
studied are intra-uterine bacterial populations during pregnancy. A systematic review of
data published on the intra-uterine microbiome was performed; molecular information and
summaries of species found in healthy individuals and in women with diagnosed infections
served to construct a database and to analyse results to date. Thirteen studies fulfilled the
review’s inclusion criteria. The data of various investigations were collated, organized, and
re-analyzed to achieve a more comprehensive understanding of microbial populations in
the intra-amniotic space. The most common intra-amniotic bacterial taxa were species
that can colonies the vagina in health and disease; there were others associated with the
habitats of the mouth, gastrointestinal tract, and respiratory tract. The results suggest
a central role for the ascending route of infections during pregnancy, and point to a
possible secondary contribution via haematogenous invasion of the intra-amniotic space.
The complete census of the intra-uterine microbiome awaits completion.
Keywords: microbiome, intra-uterine infection, preterm birth
“Infections of mothers and their babies (both in utero and
ex utero) are a major global challenge” (Hussein et al., 2011).
Preterm birth (PTB) is the second largest direct cause of deaths
in children younger than 5 years (Blencowe et al., 2012); it is a
major cause of perinatal mortality and serious neonatal morbid-
ity, and moderate to severe childhood disability in developed and
developing countries (Lawn et al., 2005; Hemminki et al., 2007;
Jacobsson, 2007). The burden of PTB is substantial and increased
between 1990 and 2010 in developing and developed countries
with reliable data (Blencowe et al., 2012). Length of gestation
is considered to be a key indicator of infant health, and PTB is
associated with poorer health outcomes in babies.
Premature deliveries can be classified into two broad groups:
spontaneous and iatrogenic. The majority of PTB occur sponta-
neously as a result of preterm labor or preterm premature rupture
of membranes. Spontaneous preterm delivery occurs in 12% of
births in developed countries (Pretorius et al., 2007) and 14%
worldwide (Pararas et al., 2006). Iatrogenic PTB may be sec-
ondary to other complications of pregnancy such as preeclampsia,
intrauterine growth restriction, abruptio placenta, or placenta
praevia (Muglia and Katz, 2010).
“For much of the 20th century, PTB, defined as birth at less
than 37 completed weeks of gestation, was viewed as an unpre-
dictable and inevitable fact of life. Medical efforts thus focused
on ameliorating the consequences of prematurity rather than
preventing its occurrence. This approach resulted in improved
neonatal outcomes, but it remains costly in terms of both the
suffering of infants and their families and the economic bur-
den on society.” (Muglia and Katz, 2010). The burden of PTB
increased during the last 30 years owing to significant improve-
ments in neonatal care that made possible the survival of very
preterm infants and resulted in a lowering of the threshold for
preterm Caesarean delivery. Other factors that have contributed
to higher rates of PTB are the multiple gestations arising from
the use of assisted reproductive technologies, advanced mater-
nal age, and improvements in obstetrics outcomes of surgical
interventions to manage invasive lesions (Muglia and Katz, 2010).
The aetiology of PTB is multifactorial, and various factors
have been identified as contributors to spontaneous PTB (Gracie
et al., 2011), e.g., genetic, infection and inflammation, decid-
ual haemorrhage, and environmental, behavioral and social stress
(Figure 1). Infections have been long suspected to be the underly-
ing cause of idiopathic PTB, and microbial intra-uterine infection
is a confirmed leading cause of PTB. In particular, bacterial
invasion of the amniotic cavity (BIAC) is the chief cause of
neonatal mortality worldwide (Gonçalves et al., 2002; Lawn et al.,
2005). Currently, there is overwhelming evidence to implicate
infection in up to 40% of PTB cases, including intra-uterine
(Ganu et al., 2013) and vaginal (Hyman et al., 2013)infections.
Intra-amniotic infections are present in 50% of all pregnan-
cies that result in PTB, and the earlier the gestational age at
delivery, the higher the frequency of intra-amniotic infection
(Burd et al., 2012).
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Mendz et al. Intra-amniotic microbiome of pregnant women
FIGURE 1 | Pathophysiological mechanisms leading to spontaneous
PTB. More than one pathway can lead to the same immediate cause of
premature delivery, for example, the preterm pre-labor rupture of
membranes (PPROM). HPA axis, hypothalamic-pituitary-adrenal axis.
A study early in the twentieth Century supported the view that
under normal circumstances and prior to labor, the amniotic cav-
ity was sterile (Harris and Brown, 1927).Thegoldstandardfor
identification of intrauterine infection has been the isolation of
microbes in amniotic fluid sampled by amniocentesis. Owing to
the finding that the amniotic fluid of less than 1% of women in
labor at term contains culturable bacteria (Romero et al., 2002),
historically the isolation of any microbes from the amniotic fluid
was considered a pathological finding. However, investigations
of the intra-uterine flora of women giving birth prematurely
based on non-cultivation taxon-specific PCR analyses, as well as
more recent studies employing non-cultivation broad-range PCR
methods have demonstrated the presence of microflora in the
intra-amniotic cavity even in the absence of any signs of infection
(DiGiulio, 2012). The results of standard microbiological stud-
ies suggest that intrauterine infection accounts for as much as
25–45% of spontaneous PTB (Zhou et al., 2010); but employ-
ing molecular techniques, bacterial footprints have been detected
in as many as 60% of women delivering preterm (Gardella et al.,
The sequence of events leading to PTB, progressing from
intrauterine infection to pro-inflammatory cytokine activa-
tion, prostaglandin production, premature contractions, cervical
changes, and premature delivery has been comprehensively stud-
ied on non-human primates (Adams Waldorf et al., 2011). In
humans, the colonization of microbes and/or inflammation of
the chorio-decidual interface can induce the production of a cas-
cade of cytokines that result in an inflammatory response (Muglia
and Katz, 2010). Bacteria also can have a more direct role in
the pathogenesis of PTB by producing enzymes that degrade
fetal membranes, or by inducing the synthesis and release of
uterotonins such as prostaglandins, able to stimulate uterine con-
tractions and cause preterm labor (Keelan et al., 2003; Lockwood,
Notwithstanding the evidence, current knowledge of
BIAC is insufficient to develop effective strategies to prevent
infection-related PTB because the prevalence, methods of
diagnosis, pathogenicity mechanisms, and host susceptibilities to
various bacteria require further investigations (DiGiulio, 2012).
A necessary step to address these knowledge gaps is to obtain a
complete understanding of the diverse microbial taxa involved
in BIAC.
Pathogens may gain access to the amniotic cavity and fetus
by ascending migration of the vaginal flora, haematogenous dis-
semination through the placenta, retrograde seeding from the
peritoneal cavity through the Fallopian tubes, or iatrogenic intro-
duction at the time of invasive procedures (Goldenberg et al.,
2000). Evidence obtained from studies culturing bacteria sup-
ports the view that the most common pathway of BIAC is the
ascending route (Romero and Mazor, 1988; DiGiulio, 2012).
This study reviews and organizes systematically data published
on the identity and frequency of detection of bacterial taxa found
in the intra-amniotic space of women who delivered preterm. Its
focus is on the dramatic advance of the knowledge of the bacte-
rial communities present in the genital microbiota of pregnant
women made in the last 18 years by non-cultivation, high-
throughput techniques of analysis, and the potential contribu-
tions systematic investigations of the female genital microbiome
can make to preventing PTB.
An initial search of PubMed was conducted employing the broad
concepts: “pregnancy,” “preterm birth,” and “intrauterine infec-
tion” or “chorioamnionitis,” as well as appropriate synonyms
and truncations via the Boolean search method. The searches
returned up to 1242 titles. Adding the term “bacteria” reduced
the number of publications to 328. The titles and abstracts of this
list were examined, and a selection was made following the inclu-
sion criteria for studies that: (1) were published between 1995 and
2013; (2) contained data on bacterial taxa in the uterus of preg-
nant women delivering preterm; and (3) employed cultivation or
molecular methods of identification of bacterial species. Excluded
were publications: (a) in a language other than English; and (b)
that did not specify the type of microbes involved in the invasion
of the amniotic space.
Perusal of the selected papers and references therein yielded
13 papers containing information required for this review (Jalava
et al., 1996; Markenson et al., 1997; Gardella et al., 2004;
DiGiulio et al., 2008, 2010a,b,c; Han et al., 2009; Jones et al.,
2009; Srinivasan et al., 2009; Zhou et al., 2010; Marconi et al.,
2011). The data from the selected studies were extracted to
construct a database of intra-uterine bacterial taxa or gen-
era identified in PTB and the frequencies at which they were
Phylogenetic trees of various bacterial phyla and their respective
orders, families, genera and species, were employed as templates
to classify the identity of intrauterine bacterial genera and species
found in pregnant women who gave birth before term. The pro-
cess served to arrange bacterial taxa into appropriate phyla and
orders according to the NCBI taxonomy database.
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Mendz et al. Intra-amniotic microbiome of pregnant women
The frequency at which a taxon or genus was present was
determined from the data in the 13 publications included
in this study by adding the number of women with intra-
uterine infections who delivered preterm in which the taxon
was found. The number of taxa in different phyla and orders
were calculated in a similar way from the data in these
The review includes 761 women delivering before term of which
349 (46%) presented with an intra-uterine infection. The use of
non-culture direct-detection techniques has increased by 5-fold
the number of taxa known to be present in intrauterine infections
during pregnancy.
Meta-analyses of randomized trials evaluating antibiotic treat-
ments report statistically significant prolongation of pregnancy
associated with the use of antibiotics in women with preterm
labor and intact membranes (King and Flenady, 2002), and
reduction in the delivered number of babies within 48 h in
preterm premature rupture of the membranes (Kenyon et al.,
2010). Thus, there is a strong association between the presence
of some bacteria in the intra-amniotic cavity and PTB.
Bacteria belonging to a total of 5 phyla and 16 orders were
found in the intra-uterine microbiota of the 349 pregnant women
with intra-amniotic infection (Ta b l e 1,Figure 2). They belonged
to 44 genera and more than 87 different taxa (identification of
some bacteria was performed only at the genus level) (Ta b l e 1).
The highest frequencies were determined for genera of the order
Mycoplasmatales (59%) and Lactobacillales (25%) (Tab l e 1 ).
Bacteria of the phylum Firmicutes were the most abundant
and were detected in 343 women with infection included in this
study; the second most common phylum among these women
was Fusobacteria, found in 71 subjects (Figure 2). The phyla with
larger number of different orders and taxa were Firmicutes and
Proteobacteria (Tab le 1 ).
Taxa of the order Mycoplasmatales were found in 205 (58.7%)
women, and bacteria of the genus Ureaplasma were detected
in 172 women (49%). Recognized genital pathogenic species
were found at high frequencies, e.g., Ureaplasma uralyticum
(11%), Streptococcus agalactiae (11%), Mycoplasma hominis (9%)
and Fusobacterium nucleatum (9%) (Tabl e 1 ). These results are
in broad agreement with previous more limited knowledge of
BIAC. A review of the pathogens involved in sepsis in neona-
tal intensive care units found that the majority were mixed
genitaltractflora(Garland and Bowman, 2003). Meta-analyses
of antibiotic administration to women with bacterial vaginosis
showed an association of the treatment with a significant reduc-
tion in the incidence of PTB and low weight babies (Smaill,
2001). This work indicated taxa present at higher frequencies
belonged to bacteria normally found in the urogenital and gas-
trointestinal tracts; a result that supports the view that most
cases of chorioamnionitis arise from pathogens ascending from
the vagina. Thus, it is reasonable to hypothesize that preventing
ascending genital tract infection and the initiation of inflam-
matory cascades will reduce PTB, neonatal fever and other
Table 1 | Bacteria found in the intra-uterine microbiota of the 349
pregnant women with intra-amniotic infection.
Phylum Order Species Frequency
Actinobacteria Actinomycetales Actinomyces spp. 1
Brachybacterium spp. 1
Mobiluncus mulieris 1
Propionibacterium acnes 1
Propionibacterium spp. 2
Rothia dentocariosa 1
Coriobacteriales Atopobium vaginae 2
Bifidobacteriales Bifidobacterium longum 1
Gardnerella vaginalis 11
Firmicutes Clostridiales Clostridium hiranonis 2
Clostridium perfringens 2
Eubacterium halii 1
Eubacteriun spp. 1
Faecalibacterium spp. 1
Filifactor alocis 1
Finegoldia magna 2
Peptoniphilus lacrimalis 1
Peptostreptococcus spp. 14
Oribacterium sinus 1
Erypsipelotricales Coprobacillus spp. 1
Mycoplasmatales Mycoplasma hominis 33
Ureaplasma parvum 22
Ureaplasma urealyticum 38
Ureaplasma spp. 112
Bacillales Listeria monocytogenes 2
Staphylococcus aureus 6
Staphylococcus equorum 2
Staphylococcus spp. 6
Lactobacillales Enterococcus faecalis 1
Enterococcus spp. 10
Lactobacillus crispatus 3
Lactobacillus delbrueckii 1
Lactobacillus gasseri 1
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Mendz et al. Intra-amniotic microbiome of pregnant women
Table 1 | Continued
Phylum Order Species Frequency
Lactobacillus iners 1
Lactobacillus spp. 3
Streptococcus agalactiae 37
Streptococcus anginosus 11
Streptococcus mitis 10
Streptococcus oralis 4
Streptococcus salivarius 1
Streptococcus spp. 1
Fusobacteria Fusobacteriales Fusobacterium
Fusobacterium spp. 4
Leptotrichia amnionii 5
Leptotrichia spp. 17
Sneathia sanguinegens 13
Bacteroidetes Bacteroidales Bacteroides fragilis 4
Bacteroides spp. 3
Prevotella bivia 4
Prevotella copri 2
Prevotella oris 1
Prevotella spp. 3
Flavobacteriales Bergeyella spp. 1
Myroides spp. 1
Proteobacteria Campylobacterales Campylobacter
Campylobacter spp. 1
Neisseriales Kingella denitrificans 1
Neisseria cinerea 1
Neisseria subflava 1
Neisseria spp. 1
Burkholderiales Delftia acidovioans 1
Pasteurellales Haemophilus
Haemophilus influenza 10
Haemophilus quentini 1
Enterobacteriales Citrobacter koseri 1
Enterobacter aerogenes 1
Enterobacter spp. 2
Escherichia coli 25
Proteus mirabilis 4
Shigella spp. 2
The frequency is given as the number of women (n) carrying a particular species.
FIGURE 2 | Chart of the five phyla of the intra-uterine bacteria of 349
women with intra-amniotic infection who gave birth preterm. Each
segment is proportional to the number of women in which bacteria of a
given phylum are found: Actinobacteria (25), Firmicutes (343), Fusobacteria
(71), Bacteroidetes (20), and Proteobacteria (58). The data indicate that taxa
from more than one phylum were present in most of these women.
Pathogens that are ordinarily found in the gastrointestinal
tract and may reach the vagina, also can cause haematoge-
nous invasion of the uterus. Listeria monocytogenes crosses the
mucosal barrier of the intestine to disseminate haematogenously
to any site, with a unique tendency to infect the fetoplacental
unit (Baud and Greub, 2011). Generally, the bacteremia mani-
fests clinically as non-specific influenza-like symptoms, and may
remain asymptomatic. A review of 36 cases of maternofetal lis-
teriosis showed that the mothers generally were affected mildly
by the infection. Twelve pregnancies ended with abortion or
stillbirth; among the children born alive, 15 were diagnosed
with bacteremia/septicemia, 3 with pneumonia, 3 with neonatal
meningitis, 1 died, and 3 were unaffected (Smith et al., 2009).
There is evidence to support the hypothesis that bacterial
infections at sites distant from the urogenital tract, in particular
the oronasal cavity and the respiratory tract, may be important
causes of preterm labor probably through the activation of abnor-
mal inflammatory responses within the uterus and intrauterine
tissues. Data from clinical and animal studies on maternal peri-
odontal status combined with a biologically plausible mechanism
provide strong evidence for a negative impact of periodontal
infection on pregnancy outcome (Baskaradoss et al., 2012).
This review showed that a number of taxa found in periodon-
tal disease were associated with PTB; they had a frequency
of ca. 13% in women delivering before term. Identified taxa
of the oronasal habitat included Bergeyella spp., Dialister spp.,
Fusobacterium nucleatum,Oribacterium sinus,Peptostreptococcus
oralis, Prevotella oris, Rothia dentocariosa, Streptococcus oralis,
Streptococcus salivarius,Veillonella parvula, and Veillonella spp. It
should be noted that many of these taxa are frequently detected in
faces, e.g., S. salivarius and F. nuc l eat u m; and in the vagina, e.g.,
P. ora l i s ,P. o r i s,S. salivarius,Veillonella spp., and Dialister spp.
Using 16S and 23S rDNA molecular methods, a Bergeyella spp.
strain detected in the amniotic fluid of a pregnant woman with
clinical intrauterine infection and histologic necrotizing acute
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Mendz et al. Intra-amniotic microbiome of pregnant women
and chronic chorioamnionitis was detected also in the subgin-
gival plaque of the patient but not in her vaginal tract. The
results suggested that the woman’s intrauterine infection with this
Bergeyella strain originated from the oral cavity (Han et al., 2006).
Capnocytophaga spp. are part of the normal human oral bacte-
rial flora, but as opportunistic pathogens can produce extra-oral
infections including septicaemia and, less commonly, chorioam-
nionitis and neonatal infections. Evidence suggests that a number
of cases of intra-amniotic infection with this bacterium occurred
by the ascending route, but several cases that involved early-onset
of sepsis due to Capnocytophaga spp. infection yielded no vaginal
cultures of this bacterium suggesting haematogenous spread from
the oral cavity (Lopez et al., 2010).
Evidence that the oral pathogen F. nu clea tum may be transmit-
ted haematogenously to the placenta and cause adverse pregnancy
outcomes was obtained in pregnant mice injected intravenously
with the bacterium. F. nu c leat um colonizes the placenta and pro-
liferates rapidly, inducing fetal death by localized infection inside
the uterus; the bacterial infection was restricted inside the uterus,
without spreading systemically (Han et al., 2004).
The bacterium Rothia dentocariosa is a common inhabitant of
the human oral cavity where it rarely causes serious infections;
it has been associated with endocarditis, pneumonia, septicemia,
and abscesses in adults. R. dentocariosa caused septicemia in a
neonatal infant with meconium aspiration syndrome (Shin et al.,
2004), and was detected in the blood of a stillborn baby (Karlsson
and Jacobsson, 2005). Its presence in the vagina is rare; only one
woman with no signs of infection was reported in a study com-
prising 394 subjects (Ravel et al., 2011). The infrequent detection
of this bacterium in the vagina makes it plausible that in the
cases of neonatal septicemia and the stillborn infant, the access
to the intra-amniotic cavity occurred via the haematogenous
Streptococcus oralis has been found in the intra-amniotic cav-
ity (Jalava et al., 1996), and was associated with PTB in a study
comparing women delivering preterm or at term (Skuldbøl et al.,
2006), but the routes of invasion were not established in these
A clinical study of 812 deliveries from a cohort study of preg-
nant mothers entitled “Oral Conditions and Pregnancy” demon-
strated that both antepartum maternal periodontal disease and
incidence/progression of periodontal disease are associated with
PTB and growth restriction after adjusting for traditional obstet-
ric risk factors. The results support the concept that maternal
periodontal infection in the absence of a protective maternal anti-
body response is associated with systemic dissemination of oral
organisms that translocate to the fetus resulting in prematurity
(Madianos et al., 2001). Analysis of oral bacteria in the amni-
otic cavity of women delivering preterm agreed with the results
of a meta-analysis of 12,047 pregnant women that found a 2.73
overall odds ratio (95% CI: 2.06–3.6, p<0.0001) of giving pre-
mature birth to a child for mothers with periodontitis (Konopka
and Paradowska-Stolarz, 2012). These findings provide support
for the hypothesis that haematogenous dissemination of oronasal
bacteria is probably one of their routes of access to the amniotic
Haematogenous spreading of infections from the upper or lower
airways to the placenta may occur at any stage of the pregnancy
(Sandu et al., 2013). The data collected in this review indi-
cated that in the intra-amniotic cavity of women giving birth
preterm were found at low frequencies bacteria that colonies
the respiratory tract such as Haemophilus influenza,Haemophilus
parainfluenza,andStreptococcus pneumoniae.
Although these and other respiratory tract pathogens have
been found in the vaginal microbiota (Ravel et al., 2011), in moth-
ers with acute respiratory infection induced by highly virulent
pathogens, the infection may spread haematogenously to the pla-
centa inducing spontaneous and/or septic abortions, premature
births, fetal damage or intra-uterine fetal death (Sandu et al.,
2013). Pregnant women with pulmonary tuberculosis have higher
odds of PTB (Asuquo et al., 2012). In a stillbirth where the mother
had an upper respiratory infection of F. nucl eatum , the bacterium
was isolated from the placenta and the infant, and the same clone
was identified in her subgingival plaque, but not in the vagina or
rectum (Han et al., 2010).
Haemophilus influenzae is primarily responsible for neonatal
meningitis and respiratory tract infections in children. It has a
low prevalence rate in genital tract cultures and rarely causes acute
endometritis, but intra-amniotic infection and positive blood cul-
tures have been reported (Shute and Kimber, 1994). A sepsis
secondary to an acute H. influenzae infection led to placental
abruption and spontaneous abortion (Calner et al., 2012); also
a case has been reported with the uterus as the primary focus
of sepsis with presence of the bacterium in blood but not in the
vagina (Martin et al., 2013). Vertical transmission of H. influenzae
appears to be the most common route of infection of the fetus,
but ascending infections are less common in H. parainfluenzae
infections (Garcia et al., 1997).
Reports indicate involvement of oral and, less commonly,
respiratory tract pathogens in intra-uterine infections. The pres-
ence of the same bacterium at the original point of infection
and in the uterus supports a causal relationship and a role for
haematogenous BIAC during pregnancy that could lead to PTB.
Streptococcus pneumoniae is a common pathogen of the gen-
eral population; it is a frequent cause of pneumonias, meningitis,
bacteremia, and sepsis. This bacterium is uncommon in the vagi-
nal flora and is rarely associated with gynecologic infections, but
has been found in intra-amniotic infections causing septic abor-
tions with no evidence of vaginal infection (Liang and Yeh, 2005).
In a study of 29 cases of S. pneumonia infection of neonates, one
mother had bacterial infection at delivery and clinical amnionitis
(Hoffman et al., 2003).
The vast majority of the genera identified in intra-amniotic
infections belong to bacteria found in the indigenous human
microbiota. Leaving out exogenously acquired bacteria, and con-
sidering that more than a trillion microbes inhabit body surfaces
and cavities, and outnumber human cells by at least a factor of
10, the human body is a rich potential source for opportunis-
tic BIAC. Pathogens residing in body sites that could access the
ascending migration or haematogenous route will influence the
diversity and abundance of bacteria in the amniotic fluid.
Frontiers in Cellular and Infection Microbiology October 2013 | Volume 3 | Article 58 |5
Mendz et al. Intra-amniotic microbiome of pregnant women
Amongst newborns, low and very low weight infants are at the
highest risk of early death or disability, thus, a major focus of
research in Obstetrics should be a better understanding of the
processes that lead to PTB and the development of preventive
interventions (Lockwood, 2013).
“Future efforts to reduce the rate of PTB depend upon gaining
an improved understanding of the causative mechanism(s), deter-
mining differences in individual susceptibility, and identifying
specific early-stage biomarkers that will allow the development of
novel and timely intervention strategies.” (Hussein et al., 2011).
In the last 15 years, the significant progress made in the knowl-
edge of the diversity of bacterial communities in the female genital
tract and the role of bacterial infections in PTB wrought by
novel sequencing techniques and bioinformatics tools, have made
reduction of PTB a goal achievable by research directed toward
prevention of BIAC by pathogens.
Considering the limitations of studies based on bacterial
cultivation to reveal all the microflora present, new comprehen-
sive investigations employing non-culture methods and state-
of-the-art sequencing analyses are required to establish the
intra-uterine microbiome in health and disease. A complete
census of the intra-uterine microbiota during pregnancy con-
ducted concurrently with a census of the vaginal microbiome
will serve to outline the characteristics of the bacterial commu-
nities in the female genital tract; in particular, the elucidation
of the microbial intra-uterine populations in healthy pregnant
women, as well as the contribution of ascending infections
to BIAC.
Future investigations that establish with more accuracy the
bacterial taxa found in association with PTB, as well as their
routes of invasion of the intra-amniotic cavity will provide impor-
tant knowledge to support the development of earlier and more
specific diagnostic methods of maternal genital infections. This
will result in better targeted and more effective treatments,
including many infections that presently are clinically silent and
can cause significant morbidity in fetuses and infants. A full
understanding of the female urogenital microbiome will render
these infections amenable to intervention and will have an impact
in the prevention of PTB.
Foundation of the Cerebral Palsy Alliance of Australia. The
authors are grateful for the contribution of E. L. Menendez to
the compilation a large data set of bacteria found in the intra-
amniotic space, their phylogeny, their primary locations in the
human body, and the diseases they cause.
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Conflict of Interest Statement: The
authors declare that the research
was conducted in the absence of any
commercial or financial relationships
that could be construed as a potential
conflict of interest.
Received: 28 July 2013; accepted: 16
September 2013; published online: 16
October 2013.
Citation: Mendz GL, Kaakoush NO and
Quinlivan JA (2013) Bacterial aetiolog-
ical agents of intra-amniotic infections
and preterm birth in pregnant women.
Front. Cell. Infect. Microbiol. 3:58. doi:
This article was submitted to the jour-
nal Frontiers in Cellular and Infection
Copyright © 2013 Mendz, Kaakoush
and Quinlivan. This is an open-access
article distributed under the terms of
the Creative Commons Attribution
License (CC BY). The use, distribu-
tion or reproduction in other forums
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ted which does not comply with these
Frontiers in Cellular and Infection Microbiology October 2013 | Volume 3 | Article 58 |7
... Further, a conclusion that no microorganisms were present in the mid-trimester amniotic fluid of healthy pregnancies was reached using NGS techniques [43,46]. However, this is not in the case of low gestational age delivery and preterm births, which have shown bacterial infections in amniotic fluid [47,48]. ...
... Further, a conclusion that no microorganisms were present in the midtrimester amniotic fluid of healthy pregnancies was reached using NGS techniques [43,46]. However, this is not in the case of low gestational age delivery and preterm births, which have shown bacterial infections in amniotic fluid [47,48]. ...
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Undoubtedly, the human body harbors trillions of microbes of different kinds performing various physiological activities, such as priming the immune system, influencing host metabolism, and improving health by providing important metabolites such as short-chain fatty acids. Although the gut is considered the “microbial organ” of our body as it hosts the most microbes, there are microbes present in various other important anatomical locations differing in numbers and type. Research has shown the presence of microbes in utero, sparking a debate on the “sterile womb” concept, and there is much scope for more work in this area. It is important to understand the early-life microbiome colonization, which has a role in the developmental origins of health and disease in later life. Moreover, seminal studies have indicated the presence of microbes beyond the gut, for example, in the adipose tissue and the liver. However, it is still unclear what is the exact source of these microbes and their exact roles in health and disease. In this review, we appraise and discuss emerging microbiome areas of research and their roles in metabolic health. Further, we review the importance of the genital microbiome in early-life microbial interactions.
... ; doi: bioRxiv preprint not consistently induce labour in mice and the impact on pups has not been investigated beyond recording survival immediately after birth. Although E. coli is not a common organism implicated in PTB, it is associated with preterm sequelae in mothers and is often associated with poor neonatal outcomes (McDonald et al., 1991;Mendz, Kaakoush and Quinlivan, 2013;Min et al., 2021). Specifically, E. coli K1 strains are commonly acquired from the mother at birth and are associated with neonatal sepsis and meningitis (McCarthy et al., 2016). ...
Preterm birth (PTB; delivery <37 weeks), the main cause of neonatal death worldwide, can lead to adverse neurodevelopmental outcomes, as well as lung and gut pathology. PTB is commonly associated with ascending vaginal infection. Previously, we have shown that ascending E. coli infection in pregnant mice induces PTB and reduces pup survival. Here, we demonstrate that this model recapitulates the pathology observed in human preterm neonates, namely neuroinflammation, lung injury and gut inflammation. In neonatal brains, there is widespread cell death, microglial activation, astrogliosis and reduced neuronal density. We also validate the utility of this model by assessing efficacy of maternal cervical gene therapy with an adeno-associated viral vector containing human beta defensin 3; this improves pup survival and reduces Tnfα mRNA expression in perinatal pup brains exposed to E. coli. This model provides a unique opportunity to evaluate the therapeutic benefit of preterm labour interventions on perinatal pathology.
... This is because the maternal side of the placenta is closer to the mother [35][36][37]. Along the same lines as the placenta, it was formerly thought that the uterus was an infertile organ; however, current research, as well as a comprehensive study [38], has started to change this point of view. The probability that germs have invaded the uterus significantly increases the likelihood that the same infectious agents will be passed on to the child. ...
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The microbiome is of great interest due to its potential influence on the occurrence and treatment of some human illnesses. It may be regarded as disruptions to the delicate equilibrium that humans ordinarily maintain with their microorganisms or the microbiota in their environment. The focus of this review is on the methodologies and current understanding of the functional microbiome in pregnancy outcomes. We present how novel techniques bring new insights to the contemporary field of maternal–fetal medicine with a critical analysis. The maternal microbiome in late pregnancy has been extensively studied, although data on maternal microbial changes during the first trimester are rare. Research has demonstrated that, in healthy pregnancies, the origin of the placental microbiota is oral (gut) rather than vaginal. Implantation, placental development, and maternal adaptation to pregnancy are complex processes in which fetal and maternal cells interact. Microbiome dysbiosis or microbial metabolites are rising as potential moderators of antenatal illnesses related to the placenta, such as fetal growth restriction, preeclampsia, and others, including gestational diabetes and preterm deliveries. However, because of the presence of antimicrobial components, it is likely that the bacteria identified in placental tissue are (fragments of) bacteria that have been destroyed by the placenta’s immune cells. Using genomic techniques (metagenomics, metatranscriptomics, and metaproteomics), it may be possible to predict some properties of a microorganism’s genome and the biochemical (epigenetic DNA modification) and physical components of the placenta as its environment. Despite the results described in this review, this subject needs further research on some major and crucial aspects. The phases of an in utero translocation of the maternal gut microbiota to the fetus should be explored. With a predictive knowledge of the impacts of the disturbance on microbial communities that influence human health and the environment, genomics may hold the answer to the development of novel therapies for the health of pregnant women.
... As stated, GBS colonization of the female genital tract has been unequivocally associated with adverse outcomes during labor thus necessitating a preemptive management strategy (16). Other bacteria commonly isolated from vaginal swab cultures (especially E. coli, and S. aureus) are considered capable of causing infections in the mother and/or child in the perinatal period (26,27). However, the association has not thus far been deemed strong enough to necessitate active screening and subsequent preemptive treatment to that end. ...
Background/aim: This retrospective cohort study enrolled hospitalized women with 24+0 to 33+6 gestational weeks with conditions associated with preterm birth. We evaluated the ability of vaginal swab isolates to guide antibiotic management decisions in the setting of threatened preterm towards a clinical advantage, i.e., longer delay between diagnosis and birth, better neonatal outcomes. Patients and methods: Vaginal swabs were obtained from all patients and antibiotic resistance profiles determined in case of growth. The cohort was divided into two groups: the antibiogram-noncongruently managed Group 1 and the antibiogram-congruently managed Group 2. These groups were compared in regard to multiple maternal and neonatal endpoints. Results: In total, 698 cases were analyzed - 224 in Group 1 and 474 in Group 2. Antibiotics were ordered/continued by the treating physician in 138 cases (138/698; 19.8%) upon review of vaginal swab cultures results. Forty-five among them (32.6%) received antibiotics inactive against the isolated bacteria. 335 (25.4%) patients had only normal vaginal flora, and 95.6% of them had not received antibiotics. Facultatively pathogenic microorganisms were isolated in 52% patients. Only 5% of the neonates had bacterial isolates identical to those of their mothers. There were no significant differences in outcomes between Group 1 and Group 2. Conclusion: No association was found between a swab-result-guided antibiotic management protocol and maternal or fetal outcome in the setting of preterm birth risk between 24 and 34 gestational weeks. These findings underline the importance of critical rethinking the frequency of vaginal smears and fine-tuning the indications for antibiotic treatment.
... The presence of pathogens in even supposedly 'sterile' places like the uterus and fetal tissues [84] has been known for decades. Pregnant women's placenta and amniotic fluid (AF) are not sterile environments, and the presence of bacterial species affects gestation and parturition, recent studies have confirmed this conclusion [85][86][87]. A study of previous experiments that evaluated bacteria detected in the AF has revealed that even in women with 'good' term pregnancies, bacteria are still present in the bloodstream [88]. ...
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Background The microbiome is still a new area of research in human health and disease, especially in reproductive health. The present article aims to aid the perception on reproductive tract microbiome that may enable better management of its dysbiosis causing reproductive dysfunctions. Main body In recent years, identification of microbiota in every part of human body has been eased by next-generation sequencing-based tools. It has been demonstrated that resident microbiota is vital for normal reproductive functions. The development of disease may result owing to changes in the microbiota brought about by internal or external factors. Female reproductive microbiota may be crucial in the success of assisted reproductive technologies such as embryo implantation and prenatal care. Though much has been learned about the vaginal microbiota, the uterine microbiome has gotten very little research attention. The impacts of well-known microorganisms including Chlamydia trachomatis , Mycoplasma tuberculosis , and Neisseria gonorrhoeae have been well documented, resulting in subclinical alterations that are considered risk factors for infertility and poor reproductive outcomes. Research on microbiota of male reproductive system is still in its early stages, and there are numerous questions concerning how inflammation and urogenital infections might impact male fertility. Certain microorganisms reportedly can directly affect spermatozoon function without even inducing oxidative stress or inflammatory cytokines, but via adhering to the spermatozoon or producing soluble factors capable of altering sperm motility and/or inducing apoptosis. Conclusion The presence of specific microbiota in the reproductive tract, regardless of their pathogenicity, or the alteration of the reproductive tract resident microbiota may pose issues with fertilization, implantation, pregnancy as well as embryo development. This may result in the failure of fertility treatments and a reduction in the number of live births.
... The exact mechanisms by which dysbiosis leads to IAI are not fully understood, but it is believed that alterations in the vaginal microbiota can lead to the overgrowth of pathogenic bacteria, which can then ascend from the vagina to the amniotic cavity and cause infection [83,84]. Dysbiosis may also lead to an inflammatory response in the vaginal and intrauterine environments, further exacerbating the risk of IAI and other obstetric complications [85]. Several strategies have been proposed for preventing IAI in women with vaginal dysbiosis. ...
Full-text available
The human microbiota inhabiting different parts of the body has been shown to have a significant impact on human health, with the gut microbiota being the most extensively studied in relation to disease. However, the vaginal microbiota is also an essential commensal microbiota in the female body that plays a crucial role in female health. Despite receiving less attention than gut microbiota, its importance in regulating reproductive immunity and its complex dynamic properties have been increasingly recognized in recent years. Advances in research on the relationship between vaginal microbiota and pregnancy outcomes & gynecological diseases in women have shed light on the importance of maintaining a healthy vaginal microbiota. In this review, we aim to compile recent developments in the study of the vaginal microbial ecosystem and its role in female health and reproductive outcomes. We provide a comprehensive account of the normal vaginal microbiota, the association between the vaginal microbiota and pregnancy outcomes, and the impact of the vaginal microbiota on gynecological diseases in women. By reviewing recent research, we hope to contribute to the advancement of academic medicine’s understanding of the vaginal microbiota’s importance in female health. We also aim to raise awareness among healthcare professionals and the general public of the significance of maintaining a healthy vaginal microbiota for better reproductive health and the prevention of gynecological diseases.
... This is in line with a recent study from Iraq showing that serum ferritin was higher significantly among PPROM compared to preterm labour women [18]. This increased the evidence of an inflammatory base that led to PPROM, especially infectionbased inflammation [19,20]. In pregnancy, the change in pH level increases the vulnerability to bacterial infection [21]. ...
... This is in line with a recent study from Iraq showing that serum ferritin was higher significantly among PPROM compared to preterm labour women [18]. This increased the evidence of an inflammatory base that led to PPROM, especially infectionbased inflammation [19,20]. In pregnancy, the change in pH level increases the vulnerability to bacterial infection [21]. ...
The aim of this study was to establish the role of thymic stromal lymphopoietin (TSLP) in the intra-amniotic host response of women with spontaneous preterm labor (sPTL) and birth. Amniotic fluid and chorioamniotic membranes (CAM) were collected from women with sPTL who delivered at term (n = 30) or preterm without intra-amniotic inflammation (n = 34), with sterile intra-amniotic inflammation (SIAI, n = 27), or with intra-amniotic infection (IAI, n = 17). Amnion epithelial cells (AEC), Ureaplasma parvum, and Sneathia spp. were also utilized. The expression of TSLP, TSLPR, and IL-7Rα was evaluated in amniotic fluid or CAM by RT-qPCR and/or immunoassays. AEC co-cultured with Ureaplasma parvum or Sneathia spp. were evaluated for TSLP expression by immunofluorescence and/or RT-qPCR. Our data show that TSLP was elevated in amniotic fluid of women with SIAI or IAI and expressed by the CAM. TSLPR and IL-7Rα had detectable gene and protein expression in the CAM; yet, CRLF2 was specifically elevated with IAI. While TSLP localized to all layers of the CAM and increased with SIAI or IAI, TSLPR and IL-7Rα were minimal and became most apparent with IAI. Co-culture experiments indicated that Ureaplasma parvum and Sneathia spp. differentially upregulated TSLP expression in AEC. Together, these findings indicate that TSLP is a central component of the intra-amniotic host response during sPTL.
Background: Data regarding the microbiome of the gestational membranes are emerging and conflicting. Shifts in the microbial communities in the setting of labor, rupture of membranes, and intraamniotic infection are yet to be understood. Objective: This study aims to characterize the microbiome of the gestational membranes of women in labor or with ruptured membranes, including of those with or without intraamniotic infection. Study design: Women with a singleton pregnancy at 28 weeks gestation or greater undergoing unscheduled Cesarean delivery in the setting of labor or rupture of membranes were included. Demographic and clinical variables were collected. We defined suspected intraamniotic infection by standard clinical criteria; placentae and gestational membranes were also reviewed for histologic evidence of infection. Sterile swabs were collected from membranes at the time of delivery. Bacteria were cultured from the swabs, and the isolates were sequenced. DNA extraction and 16S sequencing of the swabs were also performed. Bacterial taxonomy was assigned to each sequence. Alpha diversity indices and beta diversity metrics were calculated to test for differences in microbial community diversity and composition between uninfected and infected groups. Differential abundance of bacteria between infected and uninfected groups was tested at the class, family, and genus level. Results: Samples were collected from 34 subjects. Clinical intraamniotic infection was diagnosed in 38% of subjects, although 50% of placentae and membranes demonstrated histologic signs of infection. Of all samples, 68% grew bacteria on culture; this included 62% of the uninfected samples and 77% of the samples with infection (p=0.83). Multiple measures of alpha diversity were not significantly different between uninfected and infected groups. Similarly, analysis of beta diversity revealed that the microbial community of uninfected and infected group was not significantly different. A number of bacteria traditionally characterized as pathogenic, including Actinomyces and Streptococcus agalactiae, were identified in both infected and uninfected samples. Conclusion: The pathogenesis and clinical implications of intraamniotic infection remain poorly understood. Diverse bacteria are present in both infected and uninfected gestational membranes. A unique microbiologic signature may exist among the gestational membranes following labor or rupture of membranes, and further characterization of the pathogens specifically implicated in intraamniotic infection may allow for targeted therapy.
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Periodontitis and prematurity are social diseases with common risk factors. In 1996 periodontitis was proven to be a possible significant and independent risk factor of preterm birth of newborns with low body weight. Numerous studies on the influence of periodontitis on the time of birth and/or birth weight of newborns have been conducted throughout the world since, including several ones in Poland, but their results have been inconsistent. Work objective: A meta-analysis of case-control, prospective and cohort studies on the influence of periodontitis on preterm birth and low birth weight. The international and Polish bibliography bases were searched for essays on the relationship between periodontitis and preterm birth and/or low birth weight published between 1996 and 2010. All essays qualified for the meta-analysis were subjected to qualitative evaluation. The calculation of the overall odds ratio used both, fixed-effects and random-effects models (DerSimonian-Liard method). The heterogeneity of the included studies and effect of publication bias were also subjected to evaluation. The meta-analysis included 15 case-control studies, 1 cross-sectional study and 6 cohort studies. The essays came from 4 continents: 8 from Europe (including 2 from Poland), 7 from South America, 4 from North America, and 3 from Asia. The total analysis covered 12047 pregnant women. The overall odds ratio of giving premature birth to a child with low weight for mothers with periodontitis in the model of random effects amounted to 2.35 (1.88-2.93, p < 0.0001). For low birth weight, the overall OR was 1.5 (95% Cl: 1.26-1.79, p = 0.001) for premature births--2.73 (95% CI: 2.06-3.6, p < 0.0001). A significant heterogeneity of the studies included in the meta-analysis was observed, and a significant publication bias was also demonstrated. The hypothesis of periodontitis as an independent risk factor of preterm birth and/or low birth weight needs further verification. In order to achieve that, it is necessary to conduct more methodologically well-planned cohort and intervention studies. The need of dental care for pregnant women as an integral component of the prenatal care program remains to be an important issue.
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Problem: The role played by microbial invasion of the amniotic cavity (MIAC) in preterm pre-labor rupture of membranes (pPROM) is inadequately characterized, in part because of reliance on cultivation-based methods. Method of study: Amniotic fluid from 204 subjects with pPROM was analyzed with both cultivation and molecular methods in a retrospective cohort study. Broad-range and group-specific polymerase chain reaction (PCR) assays targeted small subunit ribosomal DNA (rDNA), or other gene sequences, from bacteria, fungi, and archaea. Results were correlated with measurements of host inflammation, as well as pregnancy and perinatal outcomes. Results: The prevalence of MIAC was 34% (70/204) by culture, 45% (92/204) by PCR, and 50% (101/204) by both methods combined. The number of bacterial species revealed by PCR (44 species-level phylotypes) was greater than that by culture (14 species) and included as-yet uncultivated taxa. Some taxa detected by PCR have been previously associated with the gastrointestinal tract (e.g., Coprobacillus sp.), the mouth (e.g., Rothia dentocariosa), or the vagina in the setting of bacterial vaginosis (e.g., Atopobium vaginae). The relative risk for histologic chorioamnionitis was 2.1 for a positive PCR [95% confidence interval (CI), 1.4-3.0] and 2.0 for a positive culture (95% CI, 1.4-2.7). Bacterial rDNA abundance exhibited a dose relationship with gestational age at delivery (R(2) = 0.26; P < 0.01). A positive PCR was associated with lower mean birthweight, and with higher rates of respiratory distress syndrome and necrotizing enterocolitis (P < 0.05 for each outcome). Conclusion: MIAC in pPROM is more common than previously recognized and is associated in some cases with uncultivated taxa, some of which are typically associated with the gastrointestinal tract. The detection of MIAC by molecular methods has clinical significance.
Reproductive tract infection is a major initiator of preterm birth (PTB). The objective of this prospective cohort study of 88 participants was to determine whether PTB correlates with the vaginal microbiome during pregnancy. Total DNA was purified from posterior vaginal fornix swabs during gestation. The 16S ribosomal RNA gene was amplified using polymerase chain reaction primers, followed by chain-termination sequencing. Bacteria were identified by comparing contig consensus sequences with the Ribosomal Database Project. Dichotomous responses were summarized via proportions and continuous variables via means ± standard deviation. Mean Shannon Diversity index differed by Welch t test (P = .00016) between caucasians with PTB and term gestation. Species diversity was greatest among African Americans (P = .0045). Change in microbiome/Lactobacillus content and presence of putative novel/noxious bacteria did not correlate with PTB. We conclude that uncultured vaginal bacteria play an important role in PTB and race/ethnicity and sampling location are important determinants of the vaginal microbiome.
Haemophilus influenzae rarely causes acute endometritis and the few published cases have always been associated with intrauterine devices (IUD). A 48-year-old female presented to the emergency department with a 3-day history of lower abdominal pain and fever. On physical examination she was tachycardic, hypotensive and had fundic tenderness to palpation. Imaging showed uterine leiomyomas and no IUD. Blood cultures grew a non-typable H. influenzae. Endometrial biopsy demonstrated acute endometritis. Tissue Gram stains and cervico-vaginal cultures were negative; however, polymerase chain reaction (PCR) determined presence of H. influenzae on the formalin-fixed, paraffin-embedded tissue biopsy. Evidence of H. influenzae in the endometrium demonstrates that the uterus can be the nidus for sepsis when invasive H. influenzae is found with no distinct usual primary focus. This case underscores the importance pathologic diagnosis and molecular testing.
The study focuses on the macroscopic and microscopic aspects of the placentae resulting from abortions or febrile births and their correlation with acute disorders of the upper or lower respiratory apparatus in pregnant women in various stages of pregnancy. The viral, bacterial or mycotic disorders were considered responsible for triggering septic abortion, premature or full-term deliveries, followed by septic complications of the child÷fetus or of the mother. When the mother's acute respiratory infection is induced by highly virulent pathogens, in patients with low immunity or lacking adequate medical treatment, the infection may spread through the mother's bloodstream to the placenta. The study was conducted on 90 placentae. Microscopic analysis of the tissue samples revealed acute inflammatory infiltration. Two of the study cases should be mentioned here: a four-month pregnant woman suffering from septic abortion and a nine-month pregnant woman whose fetus died in the womb because of acute pneumopathy on a non-breathing lung. Both pregnant women had the same type of disorder and neither followed any medical treatment prescribed by a physician. The prevention of placental infection is closely connected to the prevention of acute respiratory diseases or their proper treatment after their onset.
In 2005, the World Health Organization estimated that 9.6% or 12.9 million births worldwide were born preterm at <37 weeks of gestation and were accompanied by a mortality rate as high as 42% ( Significant data suggesting that intrauterine infection is an important modifier for the risk of preterm birth have emerged over the past four decades. However, causative microbial culprits have yet to be identified, and interventional trials with antimicrobials have uniformly failed to demonstrate a significant benefit. To the contrary, treatment for clinically asymptomatic, commonly associated polymicrobial communities (i.e., bacterial vaginosis) has resulted in an increase in the rate of preterm birth. This article discusses the importance of vaginal microbiome and the variance in its composition during normal pregnancy. We will expand this discussion to include possible mechanisms that might trigger preterm birth in at-risk subjects. Finally, we will review why preterm birth may be an ideal forum with which to apply our rapidly expanding metagenomic sequencing and analytic pipelines to discern the role of host and microbe in the relative continuum of health and disease.
We conducted a case-control study at three main inner-city hospitals in Birmingham, UK between 2004 and 2006, to determine the risk of adverse perinatal outcomes in pregnant women with tuberculosis (TB) (n = 24), compared with healthy pregnant controls (n = 72). The incidence of TB was 62/100,000 pregnancies, with 54.2% cases having pulmonary TB (41.7% extra-pulmonary; 4.2% both). Infants of mothers with TB had a significantly lower mean birth weight compared with controls (2,735 g vs 3,135 g; p = 0.03). Mean birth weight was lower in pulmonary TB than in the extra-pulmonary TB. Multivariate analysis showed that low birth weight was associated with pre-term delivery (p < 0.001). We conclude that pregnant women with TB are at higher risk of low birth weight due to higher odds of pre-term delivery.
Objective: Bacterial polymerase chain reaction (PCR) was used to detect early subclinical intraamhiotic infection. We used universal primers which amplify a DNA fragment of 16S ribosomal DNA (rDNA) from all known bacteria and sequenced the positive samples to identify the bacterial species. Design: Transabdominally obtained amniotic fluid samples from 20 pregnant women with prelabour rupture of the fetal membranes (PROM), showing no signs of clinical infection, and 16 control samples were analysed with universal bacterial PCR. In addition, routine bacterial culture and amniotic fluid glucose were studied. Results: Out of 20 PROM patients, five were positive in the PCR. PCR detected Ureaplasma urealyticum in two cases, Haemophilus influenzae in one case, Streptococcus oralis in one case and Fusobacterium sp. in one case. Only two of these were positive in a routine bacterial culture. Both were multibacterial infections, which caused discrepancies between the PCR and culture results. Two patients developed infectious complications: both were identified with the PCR assay. Amniotic fluid glucose was lower in PCR positive patients compared with PCR negative patients. Conclusion: Bacterial 16S rDNA PCR, in properly controlled conditions, promises to be a fast and reliable test for early intra-amniotic infection especially concerning Ureaplasma urealyticum.