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Journal of Clinical Microbiology, February 2000, p. 542-546, Vol. 38, No. 2
Department of Bacteriology, Hellenic Pasteur
Institute, 115 21 Athens,1 Department of
Microbiology, Hippokration General Hospital, 54642 Thessaloniki,2 and Department of
Microbiology, Medical School, Aristotle University of Thessaloniki,
54006 Thessaloniki,3 Greece
Received 12 July 1999/Returned for modification 30 September
1999/Accepted 28 October 1999
The aim of the present study was to investigate the frequency of
extended-spectrum The occurrence of
extended-spectrum Derepressed production of the AmpC Bacterial strains.
A total of 68 isolates of
Enterobacter spp. (56 E. cloacae and 12 E. aerogenes isolates) were studied. The isolates were nonrepetitive (one per patient) and were obtained consecutively from clinical specimens in the Hippokration General Hospital, Thessaloniki, Greece,
from January 1998 through March 1999. Species identification was done
by using the Vitek automated identification system (bioMérieux, Marcy l'Etoile, France) and was confirmed with the ATB-GN system (bioMérieux).
Antimicrobial susceptibility testing and screening for
ESBLs.
The susceptibilities of the isolates to antibiotics were
determined by the standard disk diffusion method as described in the
guidelines of the National Committee for Clinical Laboratory Standards
(16). The MICs of selected Conjugal transfer experiments.
Strains with resistance or
decreased susceptibility to expanded-spectrum cephalosporins (ESCs) as
well as ESC-susceptible strains with positive indications by at least
one of the ESBL screening tests used were mated with an E. coli K-12 recipient (strain 1R716; R IEF of ERIC2 PCR typing.
The ESC-resistant isolates were typed by
the ERIC2 PCR method (13). Extracted genomic DNA
(approximately 100 ng from each isolate) was amplified in a final
volume of 50 µl containing 20 mM Tris-HCl (pH 8.3), 50 mM KCl, 0.2 mM
(each) deoxynucleoside triphosphate, 2 mM MgCl2, 50 pmol of
the ERIC2 primer (5'-AAGTAAGTGACTGGGGTGA GCG-3'), and 0.5 U
of Taq DNA polymerase (Promega). The PCR products were
separated in 1.2% agarose.
By disk diffusion susceptibility testing, all of the 68 Enterobacter isolates studied were resistant to cefoxitin
and were classified into three main phenotypes according to their
susceptibilities to the ESCs and aztreonam. Eighteen (32%) of 56 E. cloacae isolates and 3 (25%) of 12 E. aerogenes isolates were susceptible to all newer By initial screening of the isolates for ESBLs, the Vitek ESBL test was
positive for two Caz-resistant E. cloacae strains and one
ESC-susceptible E. cloacae strain. The conventional DDST with ESC and aztreonam disks at 30 mm from the disk of Amc was positive
for six isolates, including another ESC-susceptible E. cloacae isolate. By applying the same disks at 20-mm distances, the number of isolates with positive DDST results increased to 22. Finally, the use of cefepime and cefpirome at distances 30 and 20 mm
from Amc resulted in positive DDST results for 22 and 29 enterobacters,
respectively. DDST results for two representative strains are shown in
Fig. 1.
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Detection of Extended-Spectrum
-Lactamases in
Clinical Isolates of Enterobacter cloacae and
Enterobacter aerogenes
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-lactamases (ESBLs) in a consecutive collection of
clinical isolates of Enterobacter spp. The abilities of
various screening methods to detect ESBLs in enterobacters were
simultaneously tested. Among the 68 consecutive isolates (56 Enterobacter cloacae and 12 Enterobacter
aerogenes isolates) that were analyzed for -lactamase content,
21 (25 and 58%, respectively) possessed transferable ESBLs with pIs of
8.2 and phenotypic characteristics of SHV-type enzymes, 8 (14.3%) of
the E. cloacae isolates produced a previously nondescribed,
clavulanate-susceptible ESBL that exhibited a pI of 6.9 and that
conferred a ceftazidime resistance phenotype on Escherichia
coli transconjugants, and 2 E. cloacae isolates
produced both of these enzymes. Among the total of 31 isolates that
were considered ESBL producers, the Vitek ESBL detection test was
positive for 2 (6.5%) strains, and the conventional double-disk
synergy test (DDST) with amoxicillin-clavulanate and with
expanded-spectrum cephalosporins and aztreonam was positive for 5 (16%) strains. Modifications of the DDST consisting of closer
application of the disks (at 20 instead of 30 mm), the use of cefepime,
and the use of both modifications increased the sensitivity of this
test to 71, 61, and 90%, respectively. Of the 37 isolates for which isoelectric focusing failed to determine ESBLs, the Vitek test was
false positive for 1 isolate and the various forms of DDSTs were
false-positive for 3 isolates.
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-lactamases (ESBLs) in enterobacteria that
possess inducible Bush group 1 chromosomal -lactamases is
increasingly reported worldwide (1, 2, 4-9, 10, 12, 15, 17,
18). In these species, the detection of ESBLs by methods based on
the inhibitory effects of clavulanic acid is expected to be difficult
and is dependent on the level of chromosomal enzyme production
(3). From a clinical point of view, the discrimination
between ESBLs and overproduced class C -lactamases may not be
critical, since the therapeutic options for infections caused by
organisms that possess any of these mechanisms of resistance are
similarly limited (22). Nevertheless, the detection of such
"hidden" ESBLs is still of epidemiological importance for the
hospital environment (3).
-lactamase has previously been
documented as a prevalent mechanism of -lactam resistance in
Enterobacter cloacae strains isolated in Greece
(24). On the other hand, there are no studies on the
occurrence of ESBLs in enterobacters, although high frequencies of such
enzymes have repeatedly been reported in strains of Klebsiella
pneumoniae, Escherichia coli, and Serratia
marcescens isolated in Greek hospitals (9, 19, 23). In
the present study we attempted to determine the frequency of ESBLs in a
consecutive sample of clinical isolates of E. cloacae and
Enterobacter aerogenes by using various screening procedures, as well as isoelectric focusing and conjugal transfer of
-lactamases.
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-lactams were determined for
isolates with representative susceptibility phenotypes and E. coli transconjugants by the Etest method (AB Biodisk, Solna, Sweden). All susceptibility results were interpreted by using the
breakpoints from the National Committee for Clinical Laboratory Standards (16). The isolates were screened for the presence of ESBLs by the Vitek ESBL detection test (bioMérieux) by using cefotaxime and ceftazidime alone (at 0.5 µg/ml) and in combination with clavulanic acid (4 µg/ml). Double-disk synergy tests (DDSTs) (14) were also performed by placing disks of ceftazidime,
cefotaxime, ceftriaxone, aztreonam, cefepime, and cefpirome (30 µg
each) at distances of 30 and 20 mm (center to center) from a disk
containing amoxicillin plus clavulanate (Amc; 20 g and 10 µg, respectively).
Strr). Transconjugants were selected on MacConkey agar
containing streptomycin (500 µg/ml) and ceftazidime (10 µg/ml) or
ampicillin (25 µg/ml).
-lactamases.
Isoelectric focusing (IEF) was
performed by electrophoresis of ultrasonic cell extracts on
polyacrylamide gels containing ampholytes with pHs that ranged from 3.5 to 9.5 (Amersham Pharmacia Biotech AB, Uppsala, Sweden). -Lactamases
were visualized with a 0.2-mg/ml nitrocefin solution (Oxoid Ltd.,
Basingstoke, England) and were applied on one of two parallel focused
gels immediately and on the other after it was flooded with a 1 mM
solution of potassium clavulanate. This allowed the in situ distinction
between class C -lactamases that were insensitive to clavulanate and plasmid-mediated enzymes that were susceptible to clavulanate (21).
RESULTS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-lactams
(ESC-susceptible group). Eight (14.3%) of the E. cloacae
isolates were resistant to ceftazidime and were either intermediately
susceptible or susceptible to cefotaxime, ceftriaxone, and aztreonam
(Caz-resistant group). The remaining 30 (53.6%) E. cloacae
isolates and 9 (75%) E. aerogenes isolates were resistant to all the -lactams listed above (ESC-resistant group). Seven of the
ESC-resistant E. cloacae isolates were also resistant to cefepime and cefpirome.
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FIG. 1.
Various forms of DDST for two representative isolates of
E. cloacae (TSV-287 and TSV-9) producing -lactamases of
pI 8.2 (A) and 6.9 (B), respectively. A1 and B1, tests with application
of the cephalosporin disks at a standard distance of 30 mm from the
clavulanate-containing disk (center to center); A2 and B2, tests with
proximal application of the disks at 20 mm. AMC,
amoxicillin-clavulanate; CAZ, ceftazidime; CTX, cefotaxime; CRO,
ceftriaxone; FEP, cefepime; CPO, cefpirome.
To confirm these findings, we analyzed the -lactamase contents of
the isolates. On IEF gels, all of the ESC-susceptible enterobacters, as
well as 12 of the ESC-resistant isolates (10 E. cloacae and 2 E. aerogenes isolates) presented single -lactamase
bands (pI range, 7.8 to 9.2) which were not inhibited by potassium
clavulanate and which were thus considered class C enzymes. The
remaining 35 isolates showed one or more additional -lactamase bands
which focused at pIs of 6.9, 8.2, and 5.4 and which were labile to the inhibitory action of clavulanate. In conjugation experiments in which
ceftazidime was used for selection, transconjugants were obtained only
from enterobacters that possessed enzymes of pI 8.2 or 6.9, and all of
them showed respective -lactamase bands on IEF gels. Transconjugant
clones from four strains that produced the -lactamase of pI 5.4 alone were selected on ampicillin. Matings of the two ESC-susceptible
E. cloacae strains that were positive by ESBL screening
tests showed that they were infertile. The MICs of -lactams for
representative clinical strains and E. coli transconjugants are presented in Table 1. The clones that
had acquired the enzyme of pI 6.9 expressed high levels of resistance
only to ceftazidime, while those that produced the -lactamase of pI
8.2 were resistant to all ESCs and aztreonam. Both types of
tranconjugant clones were more susceptible to penicillin-clavulanic
acid combinations than to the respective penicillins alone, indicating
efficient inhibition of the -lactamases produced by this inhibitor.
Moreover, both types of tranconjugants were positive for ESBL
production by the Vitek test as well as the conventional DDST. In all
cases, resistance to aminoglycosides, co-trimoxazole, and tetracycline had been cotransferred. On the basis of these results, both enzymes were considered to be ESBLs, and the number of ESBL producers among the
total 68 enterobacters was confirmed to be 31 (45.6%). The
-lactamase of pI 8.2 encountered in 16 (28.6%) of the E. cloacae isolates and 7 (58.3%) of the E. aerogenes
isolates and the enzyme of pI 6.9 were present in 10 (17.9%) of the
E. cloacae isolates (in 2 of them together with the enzyme
of pI 8.2).
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By ERIC2 PCR typing, all eight isolates with the Caz resistance
phenotype and the -lactamase of pI 6.9 exhibited the same pattern.
Similarly, the majority (11 of 16) of the E. cloacae isolates that possessed the enzyme of pI 8.2 exhibited a different pattern, which was also present in four of the ESC-resistant, non-ESBL-producing E. cloacae isolates. The remaining 15 ESC-resistant isolates were distributed into three unrelated ERIC2 PCR
patterns. Of the nine ESC-resistant E. aerogenes isolates,
eight, including all those that were confirmed to be ESBL producers,
showed the same ERIC2 PCR pattern (data not shown).
The scores obtained by the various ESBL screening tests are presented
in Table 2. The more efficient tests were
the DDSTs with cefepime or aztreonam at 20 mm, which were found to be
true positive for 28 (90.3%) and 21 (67.7%) of 31 ESBL producers,
respectively, and false positive for none of the 37 isolates for which
IEF and conjugal transfer experiments failed to confirm the presence of ESBLs. DDSTs with cefpirome were generally less sensitive than those
with cefepime. The conventional DDST, as well as the Vitek ESBL
detection test, were inadequate. The Vitek test was false positive for
one strain, and the DDSTs with ceftazidime, aztreonam, and cefpirome at
30 mm were false positive for another E. cloacae strain in
the ESC-susceptible group. Two more (ESC-resistant) strains for which
the DDSTs of cefepime and cefpirome indicated the presence of ESBLs
were considered false positive, since they produced only their
chromosomal -lactamase plus an enzyme of pI 5.4 that conferred a
penicillinase resistance phenotype on the respective E. coli
transconjugants (Table 1).
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DISCUSSION |
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Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
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The results of this study showed a high frequency of ESBLs in the
sample of E. aerogenes and E. cloacae isolates
examined. The most frequently encountered ESBL of pI 8.2 is most likely the SHV-5-type -lactamase, which is widely disseminated among clinical strains of K. pneumoniae, E. coli, and
S. marcescens isolated in Greek hospitals (9, 19,
23). The available data do not allow the assignment of the pI 6.9 enzyme to any of the known ESBL groups. However, the characterization
of this probably novel ESBL is beyond of the scope of this study. On
the basis of ERIC2 PCR typing, the ESBL-producing isolates seemed to
represent a limited number of types; nevertheless, the presence of the
same -lactamase in strains of different types and species is
indicative of the fact that horizontal gene spread may also be
responsible for the high frequency of detection of ESBLs among
enterobacters in this setting.
Our findings support previous suggestions that the currently used ESBL
detection methods, which are based on the inhibitory effect of
clavulanic acid on the activities of ESBLs against ESCs, are inadequate
in cases of overproduction of Bush group 1 -lactamases (3,
25). The Vitek ESBL detection test and the conventional DDST were
the least sensitive methods in our setting. In a previous study, the
Vitek test was found to be efficient with E. coli and Klebsiella spp., but its reliability with
Enterobacter spp. and Serratia spp. remained
questionable (20). In a recent report, the Vitek ESBL
detection test, as well as the conventional DDST, were unable to detect
the SHV-5 -lactamase in a K. pneumoniae strain that
produced a plasmid-borne AmpC-type -lactamase; the ESBL present in
that strain had been successfully detected by a DDST that combined Amc
with cefepime (25). In accordance with this observation, the
use of cefepime increased the sensitivity of the DDST with ESCs for the
detection of ESBLs in enterobacters from 16 to 61% when the disks were
applied at the standard distance of 30 mm from clavulanate and from 71 to 90% with closer application of the disks. The greater efficacy of
cefepime and cefpirome instead of ESCs by ESBL detection methods on the
basis of the inhibitory effect of clavulanic acid is expected, since
the former, but not the latter, retain activity against derepressed
variants of enterobacters (11). "Proximal" DDSTs with
cephalosporin disks placed 20 mm from the disk containing clavulanate
were more successful than those with disks placed the standard distance
of 30 mm.
The presence of ESBLs in enterobacters has been documented previously, but the reported numbers of ESBL producers are generally low, especially in E. cloacae (5, 6, 8, 10, 20). In most of these studies, as well as in studies that have evaluated various ESBL detection methods, the DDST with ESC has been used for the initial screening. The findings of this study indicate that the frequency of ESBLs can easily be underestimated in populations of enterobacters characterized by a high prevalence of derepressed variants. For such situations, the application of DDSTs that combine Amc with cefepime may increase the possibility of ESBL detection.
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ACKNOWLEDGMENTS |
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This work was partly supported by bioMérieux.
We thank L. S. Tzouvelekis for helpful suggestions.
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FOOTNOTES |
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* Corresponding author. Mailing address: Department of Microbiology, Medical School, Aristotle University of Thessaloniki, 54006-Thessaloniki, Greece. Phone: 30 31 99 90 91. Fax: 30 31 99 91 49. E-mail: atsakris{at}med.auth.gr.
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REFERENCES |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
|
|---|
| 1. | Arpin, C., C. Coze, A. M. Rogues, J. P. Gachie, C. Bebear, and C. Quentin. 1996. Epidemiological study of an outbreak due to multidrug-resistant Enterobacter aerogenes in a medical intensive care unit. J. Clin. Microbiol. 34:2163-2169[Abstract]. |
| 2. |
Barroso, H.,
A. Freitas-Vieira, and A. Duarte.
1999.
Molecular characterization of a ceftazidime-resistant Morganella morganii isolate producing a TEM-10 -lactamase.
Antimicrob. Agents Chemother.
43:434-435 |
| 3. | Bush, K. 1996. Is it important to identify extended-spectrum beta-lactamase-producing isolates? Eur. J. Clin. Microbiol. Infect. Dis. 15:361-364[CrossRef][Medline]. |
| 4. |
Chanal, C.,
D. Sirot,
J. P. Romaszko,
L. Bret, and J. Sirot.
1996.
Survey of extended-spectrum -lactamases among Enterobacteriaceae.
J. Antimicrob. Chemother.
38:127-132 |
| 5. |
Coudron, P. E.,
E. S. Moland, and C. C. Sanders.
1997.
Occurrence and detection of extended-spectrum -lactamases in members of the family Enterobacteriaceae at a veterans medical center: seek and you may find.
J. Clin. Microbiol.
35:2593-2597[Abstract].
|
| 6. |
de Champs, C.,
D. Sirot,
C. Chanal,
M.-C. Poupart,
M.-P. Dumas, and J. Sirot.
1991.
Concomitant dissemination of three extended-spectrum -lactamases among different Enterobacteriaceae isolated in a French hospital.
J. Antimicrob. Chemother.
27:441-457 |
| 7. | El Harrif-Heraud, Z., C. Arpin, S. Benliman, and C. Quentin. 1997. Molecular epidemiology of a nosocomial outbreak due to SHV-4-producing strains of Citrobacter diversus. J. Clin. Microbiol. 35:2561-2567[Abstract]. |
| 8. |
Emery, C. L., and L. A. Weymouth.
1997.
Detection and clinical significance of extended-spectrum -lactamases in a tertiary-care medical unit.
J. Clin. Microbiol.
35:2061-2067[Abstract].
|
| 9. | Gianneli, D., T. Tzelepi, L. S. Tzouvelekis, A. F. Mentis, and C. Nikolopoulou. 1994. Dissemination of cephalosporin-resistant Serratia marcescens strains producing a plasmidic SHV type beta-lactamase in Greek hospitals. Eur. J. Clin. Microbiol. Infect. Dis. 13:764-767[CrossRef][Medline]. |
| 10. |
Goldstein, F. W.,
Y. Pean,
A. Rosato,
J. Gertner,
L. Gutmann, and the Vigil'Roc Study Group.
1993.
Characterization of ceftriaxone-resistant Enterobacteriaceae: a multicenter study in 26 French hospitals.
J. Antimicrob. Chemother.
32:595-603 |
| 11. |
Hancock, R. E. W., and F. Bellido.
1992.
Factors involved in the enhanced efficacy against gram-negative bacteria of fourth-generation cephalosporins.
J. Antimicrob. Chemother.
29(Suppl. A):1-6 |
| 12. |
Hibbert-Rodgers, L. C. F.,
J. Heritage,
D. M. Gascoyne-Binzi,
P. M. Hawkey,
N. Todd,
I. J. Lewis, and C. Bailey.
1995.
Molecular epidemiology of ceftazidime resistant Enterobacteriaceae from patients on a pediatric oncology ward.
J. Antimicrob. Chemother.
36:65-82 |
| 13. | Hulton, C. S., C. F. Higgins, and P. M. Sharp. 1991. ERIC sequences: a novel family of repetitive elements in the genomes of Escherichia coli, Salmonella typhimurium and other enterobacteria. Mol. Microbiol. 5:825-834[Medline]. |
| 14. |
Jarlier, V.,
M. H. Nicolas,
G. Fournier, and A. Philippon.
1988.
Extended broad-spectrum -lactamases conferring transferable resistance to newer -lactam agents in Enterobacteriaceae: hospital prevalence and susceptibility patterns.
Rev. Infect. Dis.
10:867-878[Medline].
|
| 15. |
Naas, T.,
L. Philippon,
L. Poirel,
E. Ronco, and P. Nordman.
1999.
An SHV-derived -lactamase in Pseudomonas aeruginosa.
Antimicrob. Agents Chemother.
43:1281-1284 |
| 16. | National Committee for Clinical Laboratory Standards. 1997. Performance standards for antimicrobial disk susceptibility tests, 6th ed. Approved standard M2-A6 (M100-S7). National Committee for Clinical Laboratory Standards, Wayne, Pa. |
| 17. |
Neuwirth, C.,
E. Siebor,
J. Lopez,
A. Pechinot, and A. Kazmierczak.
1996.
Outbreak of TEM-24-producing Enterobacter aerogenes in an intensive care unit and dissemination of the extended-spectrum -lactamase to other members of the family Enterobacteriaceae.
J. Clin. Microbiol.
34:76-79[Abstract].
|
| 18. |
Pitout, J. D. D.,
K. S. Thomson,
N. D. Hanson,
A. F. Ehrhardt,
P. Coudron, and C. C. Sanders.
1998.
Plasmid-mediated resistance to expanded-spectrum cephalosporins among Enterobacter aerogenes strains.
Antimicrob. Agents Chemother.
42:596-600 |
| 19. |
Prinarakis, E. E.,
E. Tzelepi,
M. Gazouli,
A. F. Mentis, and L. S. Tzouvelekis.
1996.
Characterization of a novel SHV -lactamase variant that resembles the SHV-5 enzyme.
FEMS Microbiol. Lett.
139:229-234[Medline].
|
| 20. |
Sanders, C. C.,
A. L. Barry,
J. A. Washington,
C. Shubert,
E. S. Moland,
M. M. Traczewski,
C. Knapp, and R. Mulder.
1996.
Detection of extended-spectrum -lactamase-producing members of the family Enterobacteriaceae with the Vitek ESBL test.
J. Clin. Microbiol.
34:2997-3001[Abstract].
|
| 21. |
Sanders, C. C.,
W. E. Sanders, and E. S. Molland.
1986.
Characterization of -lactamases in situ on polyacrylamide gels.
Antimicrob. Agents Chemother.
30:951-952 |
| 22. |
Smith Moland, E.,
C. C. Sanders, and K. S. Thomson.
1998.
Can results obtained with commercially available MicroScan microdilution panels serve as an indicator of -lactamase production among Escherichia coli and Klebsiella isolates with hidden resistance to expanded-spectrum cephalosporins and aztreonam?
J. Clin. Microbiol.
36:2575-2579 |
| 23. |
Tsakris, A.,
L. S. Tzouvelekis,
J. Douboyas,
T. Panagea, and E. Tzelepi.
1997.
Diversity of -lactamases among Klebsiella pneumoniae strains isolated in a university hospital in Greece.
Eur. J. Epidemiol.
13:103-107[CrossRef][Medline].
|
| 24. |
Tzelepi, E.,
L. S. Tzouvelekis,
A. C. Vatopoulos,
A. F. Mentis,
A. Tsakris, and N. J. Legakis.
1992.
High prevalence of stably derepressed class-I -lactamase expression in multiresistant clinical isolates of Enterobacter cloacae from Greek hospitals.
J. Med. Microbiol.
37:91-95 |
| 25. |
Tzouvelekis, L. S.,
A. C. Vatopoulos,
G. Katsanis, and E. Tzelepi.
1999.
Rare case of failure by an automated system to detect extended-spectrum -lactamase in a cephalosporin-resistant Klebsiella pneumoniae isolate.
J. Clin. Microbiol.
37:2388 |
Journal of Clinical Microbiology, February 2000, p. 542-546, Vol. 38, No. 2
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Copyright © 2000, American Society for Microbiology. All rights reserved.
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Spanu, T., Sanguinetti, M., Tumbarello, M., D'Inzeo, T., Fiori, B., Posteraro, B., Santangelo, R., Cauda, R., Fadda, G.
(2006). Evaluation of the New VITEK 2 Extended-Spectrum Beta-Lactamase (ESBL) Test for Rapid Detection of ESBL Production in Enterobacteriaceae Isolates.. J. Clin. Microbiol.
44: 3257-3262
[Abstract] [Full Text] -
Moland, E. S., Hanson, N. D., Black, J. A., Hossain, A., Song, W., Thomson, K. S.
(2006). Prevalence of Newer {beta}-Lactamases in Gram-Negative Clinical Isolates Collected in the United States from 2001 to 2002.. J. Clin. Microbiol.
44: 3318-3324
[Abstract] [Full Text] -
Yan, J.-J., Hsueh, P.-R., Lu, J.-J., Chang, F.-Y., Shyr, J.-M., Wan, J.-H., Liu, Y.-C., Chuang, Y.-C., Yang, Y.-C., Tsao, S.-M., Wu, H.-H., Wang, L.-S., Lin, T.-P., Wu, H.-M., Chen, H.-M., Wu, J.-J.
(2006). Extended-Spectrum {beta}-Lactamases and Plasmid-Mediated AmpC Enzymes among Clinical Isolates of Escherichia coli and Klebsiella pneumoniae from Seven Medical Centers in Taiwan.. Antimicrob. Agents Chemother.
50: 1861-1864
[Abstract] [Full Text] -
Schwaber, M. J., Navon-Venezia, S., Chmelnitsky, I., Leavitt, A., Schwartz, D., Carmeli, Y.
(2006). Utility of the VITEK 2 Advanced Expert System for Identification of Extended-Spectrum {beta}-Lactamase Production in Enterobacter spp.. J. Clin. Microbiol.
44: 241-243
[Abstract] [Full Text] -
Park, Y.-J., Lee, S., Kim, Y. R., Oh, E.-J., Woo, G.-J., Lee, K.
(2006). Occurrence of extended-spectrum {beta}-lactamases and plasmid-mediated AmpC {beta}-lactamases among Korean isolates of Proteus mirabilis. J Antimicrob Chemother
57: 156-158
[Full Text] -
Paterson, D. L., Bonomo, R. A.
(2005). Extended-Spectrum {beta}-Lactamases: a Clinical Update. Clin. Microbiol. Rev.
18: 657-686
[Abstract] [Full Text] -
Bert, F., Juvin, M., Ould-Hocine, Z., Clarebout, G., Keller, E., Lambert, N., Arlet, G.
(2005). Evaluation and Updating of the Osiris Expert System for Identification of Escherichia coli {beta}-Lactam Resistance Phenotypes. J. Clin. Microbiol.
43: 1846-1850
[Abstract] [Full Text] -
Ho, P. L., Shek, R. H. L., Chow, K. H., Duan, R. S., Mak, G. C., Lai, E. L., Yam, W. C., Tsang, K. W., Lai, W. M.
(2005). Detection and characterization of extended-spectrum {beta}-lactamases among bloodstream isolates of Enterobacter spp. in Hong Kong, 2000-2002. J Antimicrob Chemother
55: 326-332
[Abstract] [Full Text] -
Jiang, X., Ni, Y., Jiang, Y., Yuan, F., Han, L., Li, M., Liu, H., Yang, L., Lu, Y.
(2005). Outbreak of Infection Caused by Enterobacter cloacae Producing the Novel VEB-3 Beta-Lactamase in China. J. Clin. Microbiol.
43: 826-831
[Abstract] [Full Text] -
Kang, C.-I., Kim, S.-H., Park, W. B., Lee, K.-D., Kim, H.-B., Kim, E.-C., Oh, M.-D., Choe, K.-W.
(2004). Bloodstream Infections Due to Extended-Spectrum {beta}-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae: Risk Factors for Mortality and Treatment Outcome, with Special Emphasis on Antimicrobial Therapy. Antimicrob. Agents Chemother.
48: 4574-4581
[Abstract] [Full Text] -
Yan, J.-J., Ko, W.-C., Wu, H.-M., Tsai, S.-H., Chuang, C.-L., Wu, J.-J.
(2004). Complexity of Klebsiella pneumoniae Isolates Resistant to Both Cephamycins and Extended-Spectrum Cephalosporins at a Teaching Hospital in Taiwan. J. Clin. Microbiol.
42: 5337-5340
[Abstract] [Full Text] -
Pai, H., Kang, C.-I., Byeon, J.-H., Lee, K.-D., Park, W. B., Kim, H.-B., Kim, E.-C., Oh, M.-d., Choe, K.-W.
(2004). Epidemiology and Clinical Features of Bloodstream Infections Caused by AmpC-Type-{beta}-Lactamase-Producing Klebsiella pneumoniae. Antimicrob. Agents Chemother.
48: 3720-3728
[Abstract] [Full Text] -
Pai, H., Hong, J. Y., Byeon, J.-H., Kim, Y.-K., Lee, H.-J.
(2004). High Prevalence of Extended-Spectrum {beta}-Lactamase-Producing Strains among Blood Isolates of Enterobacter spp. Collected in a Tertiary Hospital during an 8-Year Period and Their Antimicrobial Susceptibility Patterns. Antimicrob. Agents Chemother.
48: 3159-3161
[Abstract] [Full Text] -
Sturenburg, E., Sobottka, I., Noor, D., Laufs, R., Mack, D.
(2004). Evaluation of a new cefepime-clavulanate ESBL Etest to detect extended-spectrum {beta}-lactamases in an Enterobacteriaceae strain collection. J Antimicrob Chemother
54: 134-138
[Abstract] [Full Text] -
Bell, J. M., Turnidge, J. D., Jones, R. N., the SENTRY Asia-Pacific Participants,,
(2003). Prevalence of Extended-Spectrum {beta}-Lactamase-Producing Enterobacter cloacae in the Asia-Pacific Region: Results from the SENTRY Antimicrobial Surveillance Program, 1998 to 2001. Antimicrob. Agents Chemother.
47: 3989-3993
[Abstract] [Full Text] -
Quinteros, M., Radice, M., Gardella, N., Rodriguez, M. M., Costa, N., Korbenfeld, D., Couto, E., Gutkind, G.
(2003). Extended-Spectrum {beta}-Lactamases in Enterobacteriaceae in Buenos Aires, Argentina, Public Hospitals. Antimicrob. Agents Chemother.
47: 2864-2867
[Abstract] [Full Text] -
Pitout, J. D. D., Reisbig, M. D., Venter, E. C., Church, D. L., Hanson, N. D.
(2003). Modification of the Double-Disk Test for Detection of Enterobacteriaceae Producing Extended-Spectrum and AmpC {beta}-Lactamases. J. Clin. Microbiol.
41: 3933-3935
[Abstract] [Full Text] -
Aibinu, I. E., Ohaegbulam, V. C., Adenipekun, E. A., Ogunsola, F. T., Odugbemi, T. O., Mee, B. J.
(2003). Extended-Spectrum {beta}-Lactamase Enzymes in Clinical Isolates of Enterobacter Species from Lagos, Nigeria. J. Clin. Microbiol.
41: 2197-2200
[Abstract] [Full Text] -
Yamasaki, K., Komatsu, M., Yamashita, T., Shimakawa, K., Ura, T., Nishio, H., Satoh, K., Washidu, R., Kinoshita, S., Aihara, M.
(2003). Production of CTX-M-3 extended-spectrum {beta}-lactamase and IMP-1 metallo {beta}-lactamase by five Gram-negative bacilli: survey of clinical isolates from seven laboratories collected in 1998 and 2000, in the Kinki region of Japan. J Antimicrob Chemother
51: 631-638
[Abstract] [Full Text] -
Wang, H., Kelkar, S., Wu, W., Chen, M., Quinn, J. P.
(2003). Clinical Isolates of Enterobacteriaceae Producing Extended-Spectrum {beta}-Lactamases: Prevalence of CTX-M-3 at a Hospital in China. Antimicrob. Agents Chemother.
47: 790-793
[Abstract] [Full Text] -
Duarte, A., Faria, N., Conceicao, T., Correia, M., Lito, L. M., Cristino, J. M., Salgado, M. J., Tenreiro, R.
(2002). Identification of TEM-10 {beta}-Lactamase in a Kluyvera sp. and Other Enterobacteriaceae at a Portuguese Hospital. Antimicrob. Agents Chemother.
46: 4041-4042
[Full Text] -
Arpin, C., Labia, R., Dubois, V., Noury, P., Souquet, M., Quentin, C.
(2002). TEM-80, a Novel Inhibitor-Resistant {beta}-Lactamase in a Clinical Isolate of Enterobacter cloacae. Antimicrob. Agents Chemother.
46: 1183-1189
[Abstract] [Full Text] -
Canton, R., Oliver, A., Coque, T. M., Varela, M. d. C., Perez-Diaz, J. C., Baquero, F.
(2002). Epidemiology of Extended-Spectrum {beta}-Lactamase-Producing Enterobacter Isolates in a Spanish Hospital during a 12-Year Period. J. Clin. Microbiol.
40: 1237-1243
[Abstract] [Full Text] -
Spanu, T., Luzzaro, F., Perilli, M., Amicosante, G., Toniolo, A., Fadda, G.
(2002). Occurrence of Extended-Spectrum {beta}-Lactamases in Members of the Family Enterobacteriaceae in Italy: Implications for Resistance to {beta}-Lactams and Other Antimicrobial Drugs. Antimicrob. Agents Chemother.
46: 196-202
[Abstract] [Full Text] -
Bradford, P. A.
(2001). Extended-Spectrum {beta}-Lactamases in the 21st Century: Characterization, Epidemiology, and Detection of This Important Resistance Threat. Clin. Microbiol. Rev.
14: 933-951
[Abstract] [Full Text] -
Naumiuk, L., Samet, A., Dziemaszkiewicz, E.
(2001). Cefepime in vitro activity against derepressed extended-spectrum {beta}-lactamase (ESBL)-producing and non-ESBL-producing Enterobacter cloacae by a disc diffusion method. J Antimicrob Chemother
48: 321-322
[Full Text] -
De Gheldre, Y., Struelens, M. J., Glupczynski, Y., De Mol, P., Maes, N., Nonhoff, C., Chetoui, H., Sion, C., Ronveaux, O., Vaneechoutte, M.
(2001). National Epidemiologic Surveys of Enterobacter aerogenes in Belgian Hospitals from 1996 to 1998. J. Clin. Microbiol.
39: 889-896
[Abstract] [Full Text] -
Girlich, D., Poirel, L., Leelaporn, A., Karim, A., Tribuddharat, C., Fennewald, M., Nordmann, P.
(2001). Molecular Epidemiology of the Integron-Located VEB-1 Extended-Spectrum {beta}-Lactamase in Nosocomial Enterobacterial Isolates in Bangkok, Thailand. J. Clin. Microbiol.
39: 175-182
[Abstract] [Full Text]
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