Group B streptococcus (GBS), also known as Streptococcus
agalactiae, constitutes one of the leading pathogens associat-
ed with both early and late-onset neonatal sepsis (1, 2). Early-
onset sepsis is normally related to vaginal carriage in the
mother, and subsequent vertical transmission during birth.
The origin of late-onset disease remains less clear. It is
believed to be transmitted both vertically and horizontally,
from maternal and nosocomial sources, and resulted in per-
During a four-week period, four healthy term newborn in-
fants, all of whom were born at the same regional maternity
hospital in Korea, developed late-onset neonatal GBS infec-
tions, after being discharged from the same nursery. This out-
break was believed to reflect delayed infection after early col-
onization, originating from nosocomial sources within the
delivery room and/or the nursery.
To our knowledge, this outbreak represents the first doc-
umentednosocomial transmission of GBS infections in healthy
newborn infants born at the same maternity hospital in
Description of outbreak
Between 14 March and 10 April 2002, four healthy new-
borninfants, all of whom had been born at the same region-
al maternity hospital, and had developed late-onset neonatal
GBS infections while at home, were admitted to the Korea
University Medical Center, Ansan Hospital. The medical
charts of these infants were reviewed, and demographic, clini-
cal,and microbiological data were collected.
This presumedly nosocomial outbreak occurred in a region-
almaternity hospital, located in Ansan City. This maternity
hospital logged about 600 total deliveries in 2002. The aver-
age length of nursery stay was reported to be 3 days (6 days
for babies delivered by cesarean section). All premature or
sick babies were routinely referred to a tertiary care hospital.
All infants were less than 1 month of age, and had been
delivered and cared for in the same hospital. Their mothers’
obstetric histories were unremarkable, and the current preg-
nancies had been otherwise uncomplicated. There was no his-
tory, in any of the patients, of premature rupture of the amni-
otic membrane more than 12 hr before delivery. In addition,
Hyung Jin Kim, Soo Young Kim,
Won Hee Seo, Byung Min Choi,
Young Yoo, Kee Hyoung Lee,
Baik Lin Eun, Hai Joong Kim*
Department of Pediatrics, Department of Obstetrics &
Gynecology*, College of Medicine, Korea University,
Address for correspondence
Byung Min Choi, M.D.
Department of Pediatrics, Ansan Hospital, Korea
University Medical Center, 516 Gojan-dong,
Danwon-gu, Ansan 425-707, Korea
Tel : +82.31-412-5849, Fax : +82.31-405-8591
E-mail : email@example.com
J Korean Med Sci 2006; 21: 347-50
Copyright � The Korean Academy
of Medical Sciences
Outbreak of Late-onset Group B Streptococcal Infections in Healthy
Newborn Infants after Discharge from a Maternity Hospital
: A Case Report
During a four-week period, four healthy term newborn infants born at a regional
maternity hospital in Korea developed late-onset neonatal group B Streptococcus
(GBS) infections, after being discharged from the same nursery. More than 10
days after their discharge, all of the infants developed fever, lethargy, and poor
feeding behavior, and were subsequently admitted to the Korea University Medi-
cal Center, Ansan Hospital. GBS was isolated from the blood cultures of three
babies; furthermore, GBS was isolated from 2 cerebral spinal fluid cultures. Three
babies had meningitis, and GBS was isolated from their cerebral spinal fluid cul-
tures. This outbreak was believed to reflect delayed infection after early coloniza-
tion, originating from nosocomial sources within the hospital environment. This
report underlines the necessity for Korean obstetricians and pediatricians to be
aware of the risk of nosocomial transmissions of GBS infection in the delivery
room and/or the nursery.
Key Words : Disease Outbreaks; Nosocomial infection; Cross Infection; Nurseries; Streptococcus agalacti-
ae; Sepsis; Meningitis; Infant, Newborn
Received : 8 March 2005
Accepted : 6 April 2005
H.J. Kim, S.Y. Kim, W.H. Seo, et al.
we found no histories indicative of consanguinity, structural
anomalies, or genetic disorders on either side of any of the
families. After delivery, all infants were cared for in the same
newborn nursery. However the duration of stay of the infants
did not overlap each other. Either 3 or 6 days after birth, these
infants were discharged from the same newborn nursery, and
all appeared normal and healthy at the time of discharge.
More than 10 days after their discharge, however, all of the
infants developed fever, lethargy, and poor feeding behavior,
and were subsequently admitted to the general pediatric ward
of our hospital. One infant experienced generalized seizure
and mild respiratory difficulty, but no infants exhibited symp-
tomsnecessitating intensive care.
The time course of the outbreak is illustrated in Fig. 1. None
of the infants were matched in the hospital. All cases exhibit-
eda late-onset of the disease, occurring after 7 days after birth.
Demographic, clinical, and laboratory findings in these pa-
tients are summarized in Table 1. Fever and lethargy with re-
fusal to feed constitute the principal presenting features. Three
babies were determined to have leukopenia (total WBC count
<5,000/ L) and one had a total WBC count of 27,700/ L.
GBS was isolated from the blood cultures of 3 babies; further-
more,GBS was isolated from 2 cerebral spinal fluid cultures.
Three babies had meningitis, and GBS was isolated from their
cerebral spinal fluid cultures.
All GBS isolates proved to be sensitive to penicillin, cefo-
taxime, and erythromycin, and exhibited the same antibiot-
ic susceptibility patterns (Table 2).
When GBS infection had been confirmed in the infants,
we tested maternal vaginal swabs, which were collected about
1 month after delivery, and all tested negative for GBS. Altho-
ugh no maternal breast milk cultures were taken, we found
no clinical evidence of mastitis. One baby was not fed on breast
All infants were treated with ampicillin, coupled with either
gentamicin or cefotaxime, for at least 20 days. There were no
deaths related to this outbreak, and all infections were success-
fullyresolved. However, the Case 1 infant, who had exhibit-
ed generalized seizures and mild respiratory difficulty upon
admission, was also found to be suffering from encephalomala-
cia.A brain MRI, taken on the 36th day after birth, revealed
lacunar infarction and lamina hemorrhage in the right frontal
and temporal lobes. The remainder of the infant’s hospital
course was uncomplicated.
After the inception of infection control procedures at the
maternity hospital, no further cases of GBS have occurred in
the past 2 yr since the last case.
GBS remains the most important pathogen which causes
neonatal invasive infections in developed countries, despite
the great improvements achieved by maternal antimicrobial
prophylaxis programs. Furthermore, preterm delivery or late-
onset sepsis cannot be completely prevented, and emerging
antibiotic resistance has become a major concern in developed
countries (3, 4).
In Korea, the estimated incidence of neonatal GBS infec-
WBC, white blood cell; CSF, cerebrospinal fluid; CS, cesarean section;
GBS, group B Streptococcus.
Gestational age (week)
Birth weight (g)
Apgar score 1/5 min
Age on admission (day)
WBC count (/ L)
CSF latex aggluti-
Table 1. Clinical and laboratory features of infants infected with
S, susceptible; I, intermediate.
Table 2. Antibiotics susceptibilities of group B streptococci iso-
late from infants with sepsis and/or meningitis
Fig. 1. Time courses of outbreak between nursery stay and hospi-
taladmission. Black arrows indicate the onset of symptoms at home.
0714 2128 35424956 63 7077 84
Newborn nursery stay
Outbreak of Late-onset GBS Infections in Newborn Infants
tion has been much lower than in other developed and devel-
oping countries (5), due to the low prevalence rate of GBS
colonization in pregnant women, resulting in low rates of
early-onset neonatal GBS infection (6, 7). However, GBS is
known to be a leading cause of neonatal sepsis and meningi-
tis, and is associated with significant morbidity and mortal-
ity during the neonatal period in Korea. In addition, recent
reports (8, 9) have indicated that late-onset disease (more than
seven days after birth) accounts for 84-93% of neonatal inva-
siveGBS infections in Korea.
The pathogenesis of late-onset disease remains less clear.
Late-onset disease is believed to reflect delayed infection after
early colonization, due to either vertical or horizontal trans-
mission. In our cases, early colonization within the mother’s
genital tract is less likely, as there appeared to be no maternal
carriage of GBS. The presence of GBS in the maternal geni-
tal tract at delivery is a significant determinant of coloniza-
tion and infection in neonates. Exposure of neonates to this
organism can occur either by the ascending route, in utero
through ruptured membranes, or via contamination during
passage through the birth canal (10, 11). In our reports, al-
though maternal vaginal swabs were taken about 1 month
after delivery, the results of all of the bacterial cultures proved
to be negative.
Besides vertical transmission, other sources of GBS coloniza-
tionin neonates have been established. Horizontal transmis-
sion from hospital (12-16) or community (15, 16) sources to
neonates is one of the predominant modes for the transmis-
sion of infection. Cross-contamination from maternally infect-
ed to uninfected neonates can occur from the hands of nurs-
ery personnel. An epidemic report (17) of late-onset sepsis
due to type Ib/c GBS sepsis in a neonatal intensive care unit
revealed that none of the index cases had been colonized at
birth, establishing that nosocomial acquisition was respon-
sible. Their epidemiologic analysis suggested infant-to-infant
spread via the hands of medical/healthcare personnel, but
acquisition from two nurses who had been colonized by the
same serotype Ib/c GBS strain was not excluded. This and
other reports (18-20) have indicated that, during an outbreak,
cohorting of culture-positive infants and enforced hand wash-
ing and gloving before any infant contact significantly dimi-
nishthe rates of nosocomial acquisition.
Another potential source for GBS transmission to the neo-
nate is community acquisition. Indirect evidence suggests
that this acquisition of GBS by uncolonized infants occurs
only very infrequently (16-18, 21). Gardner and colleagues
(22) determined that only 2 out of 46 (4.6%) neonates who
had tested culture-negative for GBS when discharged from
the newborn nursery had acquired mucous membrane infec-
tions,at 6 to 8 weeks of age.
Whether the organism is acquired via vertical or horizon-
tal transmission, infants who are asymptomatically colonized
often experience persistent GBS infection at mucous mem-
brane sites for weeks or months, after which time, delayed
infection occurs (16, 19, 23). The epidemiology and patho-
genesis of GBS infection occurring beyond the first week of
life remain less well defined than they are for early-onset dis-
ease.Although serotype III strains, which account for the ma-
jority of isolates obtained from infants with late-onset infec-
tion, must be uniquely virulent for the infant between 8 days
and 3 months of age, the virulence factors in these organisms,
as well as the specific host defense mechanisms have yet to
be completely elucidated.
The route of transmission in the outbreak described here
could not be defined precisely, as the infection control mea-
sures at the regional maternity hospital were not properly
performed at the time during which the outbreak occurred.
However, the hospital personnel of the maternity hospital
were urged to keep a strict regimen of infection control pro-
cedures, including hand washing, sterilization, decontamina-
tion and cleaning techniques, as well as aseptic techniques
for invasive procedures. These general practices were designed
to prevent further spread of GBS in the hospital. This fact
strongly indicates that the infants had been infected during
admittance to the hospital, as the result of nosocomial cross-
contamination. In many instances, these general infection con-
trol procedures can disrupt an outbreak before the source has
even been identified (24, 25).
As shown in our case, neonatal GBS infections, which are
normally quite rare in Korea, were documented after patients
had been discharged from the same hospital, and the fact that
same organisms isolated from the four infants exhibited the
same antibiotic susceptibility pattern, this outbreak was most
likely due to nosocomial cross-infection, which culminated
in late-onset infection in the healthy newborn infants.
Consequently, hospital personnel should be very aware of
their potential to spread nosocomial pathogens in the hospi-
tal environment, and should implement Centers for Disease
Control and Prevention (CDC) recommendations for hospi-
tal infection control, in order to reduce the incidence of noso-
The authors thank the physicians and nursing staff work-
ing in the pediatric general ward of Korea University Medi-
calCenter Ansan Hospital, for their cooperation and support.
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