JOURNAL OF CLINICAL MICROBIOLOGY, Oct. 2011, p. 3649–3651
Copyright © 2011, American Society for Microbiology. All Rights Reserved.
Vol. 49, No. 10
Achromobacter xylosoxidans: Characterization of Strains
in Brazilian Cystic Fibrosis Patients?
Rosana H. V. Pereira,1Ana Paula Carvalho-Assef,5Rodolpho M. Albano,2Tania W. Folescu,4
Marcia C. M. F. Jones,1Robson S. Lea ˜o,1and Elizabeth A. Marques1,3*
Departamento de Microbiologia, Imunologia e Parasitologia, Faculdade de Cie ˆncias Me ´dicas, Universidade do Estado do Rio de
Janeiro, Rio de Janeiro, Brazil1; Departamento de Bioquímica, Instituto de Biologia Roberto Alca ˆntara Gomes,
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil2; Hospital Universita ´rio Pedro Ernesto,
Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil3; Instituto Fernandes Figueira,
Fundac ¸a ˜o Instituto Oswaldo Cruz, Rio de Janeiro, Brazil4; and Laborato ´rio de
Pesquisa em Infecc ¸a ˜o Hospitalar, Instituto Oswaldo Cruz,
Rio de Janeiro, Brazil5
Received 28 July 2011/Accepted 1 August 2011
We investigated the possibility of cross-infection among cystic fibrosis patients in two Brazilian reference
centers. Achromobacter xylosoxidans isolates (n ? 122) were recovered over a 5-year period from 39 patients.
Isolates were genetically heterogeneous, but one genotype was present in 56% of the patients, suggesting that
cross-infection may have occurred.
Achromobacter xylosoxidans has been isolated from respira-
tory samples from cystic fibrosis (CF) patients, but its propen-
sity to chronically colonize and cross-infect them is still un-
clear. Widespread clones of A. xylosoxidans have been
described previously (8, 11, 19), so we addressed this issue in
two CF reference centers in Brazil. We aimed to evaluate the
occurrence of chronic A. xylosoxidans colonization and the
genetic relatedness of strains isolated from the same patients
and to establish the possibility of cross-infection among CF
This study is a retrospective analysis of 179 CF patients
receiving routine care, from January 2003 to January 2008, at
Instituto Fernandes Figueira (IFF-Fiocruz) (n ? 130) and
Hospital Universita ´rio Pedro Ernesto, Universidade do Estado
do Rio de Janeiro (HUPE-UERJ) (n ? 49). IFF-Fiocruz and
HUPE-UERJ are two reference centers for pediatric and adult
patients, respectively, in Rio de Janeiro, Brazil. The study was
approved by the Committee on Ethical Practice of the Univer-
sidade do Estado do Rio de Janeiro (approval no. 2574-CEP-
Respiratory samples were cultured in accordance with bac-
teriological protocols for CF samples (4). Isolates identified as
Achromobacter spp. by the Vitek 2 Compact system using
Gram-negative (GN) cards (reference no. 21341; bioMe ´rieux)
were submitted for further identification using a panel of phe-
notypic tests as previously described (1, 10). To identify each
isolate, DNA was extracted by a boiling lysis method, and the
whole 16S rRNA gene was PCR amplified, sequenced, and
used for BLAST searches against the GenBank database (6).
Phenotypic tests and DNA sequencing identified 122 (93.8%)
isolates as A. xylosoxidans. Eight isolates could be identified
only at the genus level and were excluded from the study.
Over the study period, 39 patients (21.8%) had at least one
positive culture for A. xylosoxidans (22 females and 17 males).
Among these, there were 31 pediatric patients (mean age, 9.8
years; range, 2 to 17 years) and 8 adult patients (mean age, 23.8
years; range, 18 to 37 years). A. xylosoxidans colonization
among pediatric and adult patients was 23.9% (31/130) and
16.3% (8/49), respectively, indicating a high prevalence of pe-
diatric patient colonization compared to that described in most
international reports (2, 5). As, on average, CF patient survival
is lower in Brazil than in other countries, perhaps Brazilian
pediatric patients have more severe lung disease, resembling
the clinical status of adult patients in other countries. As a
consequence, pulmonary colonization by emergent pathogens
might be present earlier. Another possibility is that improved
diagnostic tools allow the characterization of rare CF patho-
gens (3, 15). In total, 122 A. xylosoxidans isolates were recov-
ered from 39 patients and positive cultures per patient ranged
from 1 to 20. Five patients (12.8%) were chronically colonized
by A. xylosoxidans. Patients were considered chronically colo-
nized when at least three positive cultures in 1 year were
obtained, with a minimum 1-month interval between them for
at least 2 years. In 32 cultures, the only isolated microorganism
was A. xylosoxidans, while in 90 cultures it was associated with
other CF pathogens, such as Pseudomonas aeruginosa, Staph-
ylococcus aureus, Stenotrophomonas maltophilia, and Burkhold-
eria cepacia complex. Antibiotics were administered to treat
these latter groups of bacteria but not to specifically target A.
xylosoxidans. Usually, A. xylosoxidans appeared after repeated
and prolonged treatment for P. aeruginosa lung infection (5).
Unlike others (7, 15), our population did not show persistent
associations with other pulmonary pathogens in patients
chronically colonized with A. xylosoxidans. This is possibly
linked to patient characteristics, including mean age and years
of chronic colonization.
A. xylosoxidans isolates were compared by pulsed-field gel
* Corresponding author. Mailing address: Av. 28 de Setembro, 87
fundos, Disciplina de Microbiologia, 3 andar, 20551-030 Rio de Ja-
neiro, RJ, Brazil. Phone: 55 21 28688280. Fax: 55 21 28688376. E-mail:
?Published ahead of print on 17 August 2011.
electrophoresis (PFGE) analysis of SpeI-digested genomic
DNA (9). Patterns were analyzed by GelComparII software
(Applied Maths, Sint-Martens-Latem, Belgium), with Dice co-
efficient analysis. The unweighted pair-group method using
average linkages was applied with the bandwidth tolerance set
at 1.5%. Isolates clustering together with an 85% level of
similarity were considered to belong to the same PFGE type.
Among the 122 isolates, 22 different profiles were found, indi-
cating a considerable genetic heterogeneity. Most patients (15/
39) carried individual genotypes, and sometimes, the persis-
tence of those clones was associated with the establishment of
chronicity. Nevertheless, some patients (7/39) shared the same
clone. Chronically colonized patients carried just one clone at
a particular period and occasionally exhibited other clones,
often in a single appearance and before the establishment of
chronicity (Table 1). Currently, studies minimize the possibility
of A. xylosoxidans transmission by interhuman contacts, with a
common genotype observed among pairs of brothers or pairs
of friends who were frequently hospitalized at the same time
(13, 14). In our study, patients 13 and 16 and patients 38 and
39 (two pairs of cohabiting siblings who were assisted in the
same reference center) exhibited shared clones (Table 1).
Epidemiological studies have reported the presence of pre-
dominant A. xylosoxidans clones in chronically colonized CF
patients, suggesting transmission between patients (7, 15, 16,
19). Kanellopoulou et al. (7) indicated that five CF patients
were colonized by genetically related A. xylosoxidans strains.
Lambiase et al. (8) showed that more than half of the A.
xylosoxidans isolates could be grouped into seven different clus-
ters, suggesting patient-to-patient transmission. Turton et al.
TABLE 1. Distribution of clonal groups among 122 A. xylosoxidans isolates obtained from 39 CF Brazilian patients
No. of isolates with indicated clonal groupb
a*, chronically infected patients.
bSuperscript 1 after clonal group indicates A. xylosoxidans clones shared between two patients; superscript 2 after clonal group indicates A. xylosoxidans clones shared
by more than two patients.
3650NOTESJ. CLIN. MICROBIOL.
(18) compared isolates from different patients from the same
center as well as other centers, revealing that 3 of 6 in one
center shared the same cluster. In our patients, 56.4% (22/39)
presented only the G genotype between March and October
2005 (Table 1). This is a substantially higher prevalence than
that reported by others for their dominant clones (10, 12, 18).
Reports of cross transmission with A. xylosoxidans in CF, in
general, involve few adult patients. We identified a single clone
from a large number of patients, mostly children, which was
present in both analyzed centers. Patients who also presented
with P. aeruginosa and/or B. cepacia complex infection had
more severe disease, characterized by lower body mass index
(BMI), lower forced expiratory volume in 1 s (FEV1), and
more respiratory exacerbations and hospitalizations. Even
though only patients 13 and 16 were siblings, and patients who
were hospitalized at similar dates were admitted to separate
wards, our results suggest a cross-infection, since all patients
were assisted at the same time at a CF clinic. In addition, we
could not completely rule out the occurrence of social contacts
outside the hospital or a possible contamination from common
environmental sources. Based on these considerations, we be-
lieve that this was an isolated episode that is not of sufficient
strength to justify the revision of infection control measures
because the segregation policy is carefully emphasized both in
hospitals and in social contact. Furthermore, the G genotype
did not persist, even though we still detect A. xylosoxidans in
our patients and our control measures have proven to be effi-
cient for the control of other bacteria found in CF patients.
Additionally, there are no current control measures specifically
aimed at A. xylosoxidans (17).
To our knowledge, this is the first case of an A. xylosoxidans
cross-infection in a large number of CF patients. There is still
little consensus as to whether A. xylosoxidans cross-infection
occurs to a significant extent and whether measures such as
segregated cohort clinics should be considered within an infec-
tion control strategy. Additional studies with more discrimina-
tive molecular tools are necessary to elucidate this issue.
This work was supported by the Fundac ¸a ˜o de Amparo a ` Pesquisa do
Estado do Rio de Janeiro grant E-26/110.138/2009 and Conselho Na-
cional de Desenvolvimento Científico e Tecnolo ´gico grant 471709/
We thank Ge ´ssica de Arau ´jo Rocha and Luciene Ribeiro da Costa
Silva for their technical support.
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