[Comparison of three microbiological methods for detection of expanded-spectrum betalactamases in Enterobacteriaceae isolated in Santa Fe (Argentina)].
BACKGROUND
Expanded-spectrum betalactamases (ESBLs) are the main source of resistance to oxyimino cephalosporins and monobactams in Enterobacteriaceae. Most of them derive from TEM or SHV, however the incidence of other families like CTX-M, OXA and PER has increased. In Argentina, the most frequent ESBL in Enterobacteriaceae is CTX-M-2. This specific circumstance, which differs from the situation in the Northern Hemisphere, motivated us to study new diagnostic strategies for the detection of ESBLs in our region.


METHODS
Microbiological ESBL detection was performed by double-disk synergy tests, cefotaxime and ceftazidime disks with and without clavulanic acid (NCCLS), and cefotaxime and ceftazidime disks in Müeller-Hinton agar supplemented with lithium clavulanate (MH-cla). Betalactamases were characterized by isoelectric focusing, hydrolysis profile and PCR amplification.


RESULTS
Among 575 clinical isolates of Enterobacteriaceae, 14% were oxyimino cephalosporin-resistant. Two different ESBLs were detected in 31 resistant strains: CTX-M-2 (28) and PER-2 groups (3). The double-disk synergy test was the least sensitive method for ESBL detection. ESBLs were detected by the other two methods in all isolates with the use of cefotaxime disks, but not with ceftazidime disks.


CONCLUSIONS
The microbiological method employing MH-cla with cefotaxime disks had a sensitivity and specificity comparable to the referral test using the same antibiotic proposed by the NCCLS for the detection of ESBLs.
Truppia
Luis Alberto
LA
Hospital J.M. Cullen, Santa Fe, Argentina.
Mollerach
Analia
A
Di Conza
José Alejandro
JA
Radice
Marcela
M
Mugna
Viviana
V
Méndez
Emilce
E
Gutkind
Gabriel Osvaldo
GO
D001118:Argentina / Q000453:epidemiology; D001426:Bacterial Proteins / Q000032:analysis* / Q000145:classification / Q000378:metabolism; D002439:Cefotaxime / Q000378:metabolism / Q000494:pharmacology; D002442:Ceftazidime / Q000378:metabolism / Q000494:pharmacology; D002511:Cephalosporins / Q000145:classification / Q000378:metabolism* / Q000494:pharmacology; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D006868:Hydrolysis; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests / Q000379:methods*; D008997:Monobactams / Q000145:classification / Q000378:metabolism* / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013379:Substrate Specificity; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000032:analysis* / Q000145:classification / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D002511:Cephalosporins; D008997:Monobactams; D002442:Ceftazidime; C071167:beta-lactamase CTX-2; C509814:beta-lactamase PER-2, Enterobacteriaceae; D001618:beta-Lactamases; D002439:Cefotaxime