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Journal of Clinical Microbiology, December 2001, p. 4549-4553, Vol. 39, No. 12
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.12.4549-4553.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Automated Ribotyping Provides Rapid Phylogenetic
Subgroup Affiliation of Clinical Extraintestinal Pathogenic
Escherichia coli Strains
Olivier
Clermont,1
Christophe
Cordevant,2
Stephane
Bonacorsi,1
Armelle
Marecat,2
Marc
Lange,2 and
Edouard
Bingen1,*
Laboratoire d'Études de Génétique
Bactérienne dans les Infections de l'Enfant (EA3105),
Université Denis Diderot-Paris 7, Hôpital Robert
Debré, Paris,1 and Institut Pasteur de
Lille, Lille,2 France
Received 5 April 2001/Returned for modification 23 July
2001/Accepted 27 September 2001
 |
ABSTRACT |
Using the automated Riboprinter system, we have initiated the
construction of an electronic Riboprint database composed of 72 ECOR
reference strains and 15 archetypal virulent strains in order to
provide a new simple molecular characterization method. More than 90%
of the ECOR strains clustered in their original phylogenetic group. All
but one of the archetypal virulent strains had a profile identical to
that of one of the ECOR strains and could be easily affiliated with a
phylogenetic group. This method appears to be an accurate and practical
tool especially for investigating the genetic relationship between
clinical extraintestinal pathogenic strains and B2 subgroup ECOR
strains or archetypal pathotype strains.
 |
TEXT |
Escherichia coli is both
the most common commensal bacterium and the most frequent
community-acquired pathogen in humans. E. coli belongs to
the normal fecal flora but can cause various intestinal
(gastroenteritis and colitis) and extraintestinal (urinary tract
infection, septicemia, and neonatal meningitis) infections. The genetic
structure of E. coli is considered clonal, and phylogenetic analyses have shown that strains of this species fall into four main
phylogenetic groups (A, B1, B2, and D) (11, 24). Recent attempts to establish a link between phylogeny and virulence suggest that extraintestinal pathogenic E. coli strains are mostly
derived from phylogenetic group B2 and, to a lesser extent, group D
(3, 4, 18). In contrast, most human commensal strains
originate from phylogenetic groups A and B1. Contrary to
extraintestinal pathogenic strains, each pathotype of intestinal
pathogenic strains shows phylogenetic diversity: enteropathogenic
E. coli, enterohemorrhagic E. coli (EHEC),
enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAggEC), diffuse adherent E. coli (DAEC), and
enteroinvasive E. coli are distributed among all the
phylogenetic groups (8, 20, 22). Studies based on
molecular characterization and genetic relatedness of pathogenic and
commensal strains have improved our understanding of the pathogenicity
and acquisition of virulence traits in E. coli.
The reference techniques for phylogenetic grouping are multilocus
enzyme electrophoresis (MLEE) (11, 23) and ribotyping (3, 9, 16, 19), but both techniques are complex and time-consuming. Moreover, neither method is standardized. Thus, to
determine the phylogenetic group of a given strain, a collection of
typed reference strains, such as the ECOR collection, must be tested in
parallel (3, 9, 12, 20). The ECOR collection is a set of
72 reference E. coli strains isolated between 1973 and 1983 from a variety of animal hosts and geographic locations. Those strains
are well characterized and represent the entire range of genotypic
variation in the species as a whole (17).
Being automated and standardized, the Riboprinter microbial
characterization system is suited to rapid and high-throughput typing
of bacterial strains. The Riboprinter can yield 32 ribotypes a day
directly from fresh colonies. Given their worldwide distribution and
interconnection, Riboprinters permit immediate comparisons of ribotypes
through connection of their databases. The purpose of the present study
was to initiate the construction of an electronic Riboprint database of
archetypal virulent strains and the ECOR collection, in order to
provide the scientific community with a rapid tool for investigating
genetic relationships between clinical and reference E. coli strains.
Bacterial isolates.
The 72 strains of the ECOR collection
(17) were kindly provided by R. Selander (Department of
Biology, University of Rochester, Rochester, N.Y.). Of these, 68 belong
to the four main phylogenetic groups (A, B1, B2, and D) and 4 are
unclassified (group E) (11, 24). Information concerning
these strains can be obtained at the T. Whittam laboratory web
site (http://foodsafe.msu.edu/whittam/ecor/index.html). We
also used several archetypal strains representing different E. coli pathotypes, including neonatal meningitis strains RS218 (kindly provided by K. Kim, Johns Hopkins University School of Medicine, Baltimore, Md.), C5 and RS176 (obtained from R. Bortolussi, Dhalousie University, Halifax, Nova Scotia, Canada), uropathogenic strains J96 and E536 (provided by J. Hacker, Institut für
Molekulare Infektionsbiologie, Würzburg, Germany), uropathogenic
strain CFT073 (obtained from H. Mobley, University of Maryland,
Baltimore), enteropathogenic strain E2348/69, EHEC strain EDL933,
ETEC strains EDL1493, E2539-C1, and TX-1, EAggEC strains O42 and
JM221, and DAEC A30 and C1845. All the diarrheagenic strains were
kindly provided by C. Le Bouguenec (Unité de Pathogénie
Bactérienne des Muqueuses, Institut Pasteur, Paris, France).
E. coli laboratory K-12 strain MG1655, which belongs to
phylogenetic group A, was also studied (11).
Automated ribotyping.
All E. coli isolates and ECOR
strains were characterized by automated ribotyping with the Riboprinter
(Qualicon Inc., Wilmington, Del.). Ribotyping was performed under the
conditions recommended by the manufacturer (6, 25), with
the following modifications. The validated EcoRI restriction
enzyme was replaced by HindIII (New England BioLabs,
Beverly; Mass.) at 100 U/µl in standardized reagents in 0.5-ml tubes
(Sarstedt, Orsay, France). The other steps were unmodified and
automated, and up to 32 isolates could be analyzed per day.
For each strain analyzed, one fresh colony was picked and resuspended
in sample buffer and added to the processing module for a heat
treatment step at 80°C for 10 min in order to inhibit endogenous
DNA-degrading enzymes. The temperature was then reduced, and two lytic
enzymes (lysostaphin and N-acetylmuramidase) were added to
the sample. The sample carrier was then loaded onto the Riboprinter
system with the other commercial reagents. Restriction enzyme
digestion, gel electrophoresis, and blotting steps were completely
automated. Briefly, bacterial DNA was digested with the chosen
restriction enzyme and loaded onto an agarose gel; restriction
fragments were separated by electrophoresis and simultaneously transferred to a nylon membrane. After a denaturation step, the blotted
nucleic acids were hybridized with a sulfonated DNA probe harboring the
genes for the small and large rRNA subunits of E. coli. The
hybridized probe was detected with alkaline phosphatase-labeled antibodies directed against sulfonated DNA. Bound labeled antibodies were then detected by capturing light emission from a chemiluminescent substrate with a charge-coupled device camera. The output consisted of
a densitometric scan depicting the distribution of the restriction fragments and their molecular weights and was saved in the Riboprinter computer.
Ribotype analysis.
For each batch of eight samples, ribotypes
were normalized to the position of the molecular weight standards by
using the Qualicon software. Computerized ribotypes were exported for
analysis in .txt files, converted to .int files with GelConvert 1.01 software (Qualicon), and imported into Gel Compar software, version 4.1 (Applied Maths, Ghent, Belgium). Clustering analysis was performed with
the unweighted pair group method using arithmetic averages (UPGMA)
based on the Dice coefficient for the band matching (10), with a position tolerance setting of 0.8% and an optimization setting
of 0.25% (default values are 1% for position tolerance and 0.5% for
optimization). Bands for analysis with the Dice coefficient were
assigned manually, according to densitometric curves and the
accompanying hard-copy photograph. As previously reported, HindIII generates a few bands of very low intensity,
especially under 1 kb (15). One third of the ECOR
reference strains, which were ribotyped twice, showed that these
faint bands were nonreproducible (data not shown). Thus, these bands
were not taken into account in the band-based cluster analysis. On the
other hand, major bands were always reproducible and were perfectly in
accordance with manual ribotypes patterns previously obtained
(3) (data not shown).
Access to the Riboprinter database for downloading ECOR ribotypes will
be made available upon request
(
edouard.bingen{at}rdb.ap-hop-paris.fr or
marc.lange{at}pasteur-lille.fr). Furthermore, all data (including
the
dendrogram) are available at the Molecular Typing Center website
(
http://www.pasteur-lille.fr /english/techno/ctm/ecor.html).
Ribotyping of the 72 ECOR strains using the
HindIII
enzyme yielded 32 ribotypes after exclusion of the faint bands
generated
by this enzyme (see Materials and Methods). The number of
strains
presenting a given ribotype ranged from 1 to 12. All strains
with
the same pattern belonged to the same phylogenetic group. Only
one
exception was noted: the patterns for ECOR 24, 26, 31, and
37 belonged
to groups A, B1, E, and E, respectively. A phylogenetic
tree of the 72 ECOR strains, 15 pathogenic reference strains,
and K-12 strain MG1655
was obtained by UPGMA (Fig.
1). Three major
clusters containing 69 ECOR strains were clearly distinguished
on the
tree. Strains belonging to groups A and B2 were clearly
separated from
each other and from a cluster containing the B1
and D strains. Three
strains (ECOR 35, 36, and 66, belonging to
groups D, D, and B2,
respectively) displayed an atypical ribotype
and were separated from
the three major clusters. Group B1 and
D strains clustered very close
together but remained distinguishable
from each other. In subcluster
B1, one pattern was yielded by
strains belonging to group A and the
group of unclassified strains
(Fig.
1). Thus, strains yielding this
pattern could not be unambiguously
grouped. Apart from this exception,
each of the other 31 patterns
always contained strains belonging to a
given phylogenetic group.
Thus, a clinical strain yielding one of these
31 patterns can
be unambiguously categorized in one of the four
phylogenetic groups.

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FIG. 1.
Comparative analysis of HindIII ribotypes
obtained with the Riboprinter for the ECOR collection and a subset of
E. coli pathogenic reference strains. Clustering was
performed by UPGMA, and similarity analysis was based on the use of the
Dice coefficient (see Materials and Methods). For each strain, name,
serotype, phylogenetic group or pathovar, and source is indicated. O:H
serotypes are as listed at the T. Whittam laboratory website. ON, HN,
nontypeable with standard antisera; NM, nonmotile strain; EPEC,
enteropathogenic E. coli; NMEC, neonatal meningitis
E. coli; DAEC, diffuse adherent E. coli
EAggEc, enteroaggregative E. coli; ETEC, enterotoxigenic
E. coli; EHEC, enterohemmorhagic E. coli; UPEC,
uropathogenic E. coli; ABU, asymptomatic bacteriuria;
UTI, symptomatic urinary tract infection.
|
|
To evaluate this grouping method, we tested 15 pathogenic
E. coli strains. The automated ribotyping technique readily grouped
these strains, all but one of which yielded patterns identical
to one
of those obtained with the ECOR collection. As expected,
the six
extraintestinal pathogenic strains were classified in
groups B2 and D. Interestingly, the neonatal meningitis strains
(RS218 and C5) and the
three uropathogenic strains (J96, E536,
and CFT073) belonged to four
different subgroups within group
B2. The intestinal pathogenic strains
were distributed among all
the phylogenetic groups, and strains
belonging to one pathotype
were distributed among different
phylogenetic groups. For example,
EAggEC strains JM221 and O42 belonged
to groups A and D, respectively,
while ETEC strains belonged to groups
A (E2536-1 and EDL1493)
and B1 (TX-1). However, EHEC strain EDL933
showed a ribotype associated
with strains belonging to groups A and B1
and the group of unclassified
strains and could not thus be affiliated
with a given group. Nevertheless,
this profile may be considered
representative of the O157:H7 strains,
since 10 other strains tested
had an identical pattern (data not
shown) (
7).
Phylogenetic analysis is increasingly important in the analysis of
bacterial virulence. Thus, for emerging pathogens for which
virulence
factors are partially known, determination of the genetic
background
could be of the utmost importance (
5,
18,
21).
New
phylogenotyping methods have recently been developed, such
as
repetitive-element PCR fingerprinting (
13), fluorescent
amplified
fragment length polymorphism (
1), and multilocus
sequence typing
(
14), but manual ribotyping and MLEE
remain the gold standard
in this field. However, these techniques are
complex and time-consuming
and are therefore unsuitable for studies of
the relationship between
virulence and genetic background. The
availability of an automated,
standardized ribotyping technique
provides the opportunity to
initiate a database of ECOR strains, making
the Riboprinter a
simple and rapid phylogenotyping
tool.
We chose to ribotype the ECOR collection with
HindIII,
because of its discriminating power and the fact that the profiles
it
yields can easily be attributed to a given phylogenetic group
(
2,
3,
7). Most of the ECOR strains clustered in their
original
phylogenetic group (
11), and the similarity level in
the
four major divisions (~70%) was not different from those found
by
Herzer et al. (
11). The group B1 and D strains were the
most
difficult to discriminate. However, strains belonging to these
two
groups never yielded identical patterns. Despite a lesser
discriminating power of ribotyping compared to MLEE typing, only
one
ribotype pattern, containing ECOR 24, 26, 31, and 37, carried
a risk of
erroneous phylogenetic group attribution. Considering
that more than
90% of the pathogenic strains tested here yielded
profiles identical
to that of one of the ECOR strains, the phylogenetic
group of each
strain could be determined without recourse to a
statistical clustering
method. Indeed, analyzing retrospectively
the ribotypes obtained from
our collection of 69
E. coli neonatal
meningitis strains
described previously (
3), we observed that
88% of these
strains yielded a profile identical to that of one
of the ECOR strains
(data not shown). A recently published method
determines the
phylogenetic group of a strain using a rapid and
simple PCR-based
technique (
7) but appears to be more suited
to screening
studies. Indeed, the automated ribotyping method
has the advantage of
attributing a strain to a phylogenetic subgroup
defined by one or a few
ECOR strains. In this study we observed
an excellent correlation
between B2 subgroups described by Herzer
et al. (
11) and
B2 ribotyping subgroups. Of particular interest,
the five B2 archetypal
extraintestinal pathogenic strains were
distributed among the four
major B2 subgroups (represented by
more than one strain). Thus, this
rapid method appears to be a
more accurate tool for investigating the
phylogenetic relationship
of a strain, especially uropathogenic and
neonatal meningitis
strains, to the
E. coli population as a
whole. Moreover, the electronic
ribopattern database that we have
initiated provides rapid investigation
of the genetic relationship
between clinical extraintestinal and
B2 subgroup ECOR or archetypal
pathotype
strains.
 |
ACKNOWLEDGMENTS |
This work was supported in part by the Programme de Recherche
Fondamentale en Microbiologie, Maladies Infectieuses et Parasitaires (Appel d'offre 1998), "Recherche de déterminants
génétiques de pathogénicité chez E.
coli K1 responsable de méningite néonatale."
We thank K. Kim, J. Hacker, R. Bortolussi, H. Mobley, and C. Le
Bouguenec for providing some of the strains used in this study. We are
grateful to Maryse De-Ré, Institut Pasteur de Lille, for her
valuable technical assistance in parts of this study. We also thank
Martine Alliot and Catherine Diesel-Klein (Qualicon Europe) for helpful
discussions and Qualicon Europe for providing the Riboprinter reagents
used in this work.
 |
FOOTNOTES |
*
Corresponding author. Mailing address: Service de
Microbiologie, Hôpital Robert Debré, 48 Blvd.
Sérurier, 75395 Paris cedex 19, France. Phone: 33 1 40 03 23 40. Fax: 33 1 40 03 24 50. E-mail: edouard.bingen{at}rdb.ap-hop-paris.fr.
 |
REFERENCES |
| 1.
|
Arnold, C.,
L. Metherell,
G. Willshaw,
A. Maggs, and J. Stanley.
1999.
Predictive fluorescent amplified-fragment length polymorphism analysis of Escherichia coli: high-resolution typing method with phylogenetic significance.
J. Clin. Microbiol.
37:1274-1279[Abstract/Free Full Text].
|
| 2.
|
Bingen, E.,
E. Denamur,
N. Brahimi, and J. Elion.
1996.
Genotyping may provide rapid identification of Escherichia coli K1 organisms that cause neonatal meningitis.
Clin. Infect. Dis.
22:152-156[Medline].
|
| 3.
|
Bingen, E.,
B. Picard,
N. Brahimi,
S. Mathy,
P. Desjardins,
J. Elion, and E. Denamur.
1998.
Phylogenetic analysis of Escherichia coli strains causing neonatal meningitis suggests horizontal gene transfer from a predominant pool of highly virulent B2 group strains.
J. Infect. Dis.
177:642-650[Medline].
|
| 4.
|
Boyd, E. F., and D. L. Hartl.
1998.
Chromosomal regions specific to pathogenic isolates of Escherichia coli have a phylogenetically clustered distribution.
J. Bacteriol.
180:1159-1165[Abstract/Free Full Text].
|
| 5.
|
Brisse, S.,
C. M. Verduin,
D. Milatovic,
A. Fluit,
J. Verhoef,
S. Laevens,
P. Vandamme,
B. Tummler,
H. A. Verbrugh, and A. van Belkum.
2000.
Distinguishing species of the Burkholderia cepacia complex and Burkholderia gladioli by automated ribotyping.
J. Clin. Microbiol.
38:1876-1884[Abstract/Free Full Text].
|
| 6.
|
Bruce, J. L.
1996.
Automated system rapidly identifies and characterizes microorganisms in food.
Food Technol.
50:77-81.
|
| 7.
|
Clermont, O.,
S. Bonacorsi, and E. Bingen.
2000.
Rapid and simple determination of the Escherichia coli phylogenetic group.
Appl. Environ. Microbiol.
66:4555-4558[Abstract/Free Full Text].
|
| 8.
|
Czeczulin, J. R.,
T. S. Whittam,
I. R. Henderson,
F. Navarro-Garcia, and J. P. Nataro.
1999.
Phylogenetic analysis of enteroaggregative and diffusely adherent Escherichia coli.
Infect. Immun.
67:2692-2699[Abstract/Free Full Text].
|
| 9.
|
Desjardins, P.,
B. Picard,
B. Kaltenbock,
J. Elion, and E. Denamur.
1995.
Sex in Escherichia coli does not disrupt the clonal structure of the population: evidence from random amplified polymorphic DNA and restriction-fragment-length polymorphism.
J. Mol. Evol.
41:440-448[CrossRef][Medline].
|
| 10.
|
Dice, L. R.
1945.
Measures of the amount of ecological associations between species.
J. Ecol.
26:297-302[CrossRef].
|
| 11.
|
Herzer, P. J.,
S. Inouye,
M. Inouye, and T. S. Whittam.
1990.
Phylogenetic distribution of branched RNA-linked multicopy single-stranded DNA among natural isolates of Escherichia coli.
J. Bacteriol.
172:6175-6181[Abstract/Free Full Text].
|
| 12.
|
Hilali, F.,
R. Ruimy,
P. Saulnier,
C. Barnabe,
C. Lebouguenec,
M. Tibayrenc, and A. Andremont.
2000.
Prevalence of virulence genes and clonality in Escherichia coli strains that cause bacteremia in cancer patients.
Infect. Immun.
68:3983-3989[Abstract/Free Full Text].
|
| 13.
|
Johnson, J. R., and T. T. O'Bryan.
2000.
Improved repetitive-element PCR fingerprinting for resolving pathogenic and nonpathogenic phylogenetic groups within Escherichia coli.
Clin. Diagn. Lab. Immunol.
7:265-273[Abstract/Free Full Text].
|
| 14.
|
Lecointre, G.,
L. Rachdi,
P. Darlu, and E. Denamur.
1998.
Escherichia coli molecular phylogeny using the incongruence length difference test.
Mol. Biol. Evol.
15:1685-1695[Abstract].
|
| 15.
|
Machado, J.,
F. Grimont, and P. A. Grimont.
1998.
Computer identification of Escherichia coli rRNA gene restriction patterns.
Res. Microbiol.
149:119-135[Medline].
|
| 16.
|
Maslow, J. N.,
T. S. Whittam,
C. F. Gilks,
R. A. Wilson,
M. E. Mulligan,
K. S. Adams, and R. D. Arbeit.
1995.
Clonal relationships among bloodstream isolates of Escherichia coli.
Infect. Immun.
63:2409-2417[Abstract].
|
| 17.
|
Ochman, H., and R. K. Selander.
1984.
Standard reference strains of Escherichia coli from natural populations.
J. Bacteriol.
157:690-693[Abstract/Free Full Text].
|
| 18.
|
Picard, B.,
J. S. Garcia,
S. Gouriou,
P. Duriez,
N. Brahimi,
E. Bingen,
J. Elion, and E. Denamur.
1999.
The link between phylogeny and virulence in Escherichia coli extraintestinal infection.
Infect. Immun.
67:546-553[Abstract/Free Full Text].
|
| 19.
|
Picard, B.,
C. Journet-Mancy,
N. Picard-Pasquier, and P. Goullet.
1993.
Genetic structures of the B2 and B1 Escherichia coli strains responsible for extra-intestinal infections.
J. Gen. Microbiol.
139:3079-3088[Abstract/Free Full Text].
|
| 20.
|
Pupo, G. M.,
D. K. Karaolis,
R. Lan, and P. R. Reeves.
1997.
Evolutionary relationships among pathogenic and nonpathogenic Escherichia coli strains inferred from multilocus enzyme electrophoresis and mdh sequence studies.
Infect. Immun.
65:2685-2692[Abstract].
|
| 21.
|
Rogerie, F.,
A. Marecat,
S. Gambade,
F. Dupond,
M. Beaubois, and M. Lange.
2001.
Characterization of shiga-toxin producing Escherichia coli and O157 serotype Escherichia coli isolated in France from healthy domestic cattle.
Int. J. Food Microbiol.
63:217-223[CrossRef][Medline].
|
| 22.
|
Rolland, K.,
N. Lambert-Zechovsky,
B. Picard, and E. Denamur.
1998.
Shigella and enteroinvasive Escherichia coli strains are derived from distinct ancestral strains of Escherichia coli.
Microbiology
144:2667-2672[Abstract/Free Full Text].
|
| 23.
|
Selander, R. K.,
D. A. Caugant,
H. Ochman,
J. M. Musser,
M. N. Gilmour, and T. S. Whittam.
1986.
Methods of multilocus enzyme electrophoresis for bacterial population genetics and systematics.
Appl. Environ. Microbiol.
51:873-884[Free Full Text].
|
| 24.
|
Selander, R. K.,
D. A. Caugant, and T. S. Whittam.
1987.
Genetic structure and variation in natural populations of Escherichia coli, p. 1625-1648.
In
F. C. Neidhardt, J. L. Ingraham, K. B. Low, B. Magasanik, M. Schaechter, and H. E. Umbarger (ed.), Escherichia coli and Salmonella typhimurium: cellular and molecular biology. American Society for Microbiology, Washington, D.C.
|
| 25.
|
Sethi, M. R.
1997.
Fully automated microbial characterization and identification for industrial microbiologists.
Am. Lab.
5:31-35.
|
Journal of Clinical Microbiology, December 2001, p. 4549-4553, Vol. 39, No. 12
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.12.4549-4553.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
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