학술논문
Effect of inoculum size of Enterobacteriaceae producing SHV and CTX-M extended-spectrum β-lactamases on the susceptibility to β-lactam combinations with inhibitors and carbapenems.
Document Type
Article
Author
Source
Subject
*BETA lactamases
*ESCHERICHIA coli
*PNEUMONIA
*IN vivo toxicity testing
*ENTEROBACTERIACEAE
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Language
ISSN
1840-0132
Abstract
Aim Many extended-spectrum ß-lactamases (ESBL) producing isolates of E. coli and K. pneumoniae are susceptible in vitro to amoxycillin-clavulanate (AMC), ceftazidime-clavulanate (CAZ/cl), and piperacillin-tazobactam (TZP), but MICs increase sub- stantially when higher inoculum is applied. The aim of this study was to determine the effect of inoculum size on the susceptibility orE. coli and K. pneumoniae isolates with well characterized ES- BLs, to amoxycillin (AMX), AMC - amoxycilin + clavulanate, ceftazidime (CAZ), CAZ/cl - ceftazidime + clavulanate, piperacillin (PIP), TZP - tazobactam + piperacilin, imipenem (IMI) and meropenem (MEM). Methods Minimum inhibitory concentrations (MIC) were determined by broth microdilution method using inocula that differed 100 fold in density. Results Inoculum effect for CAZ/cl was detected in 52% of SHV-2 producing K. pneumoniae strains followed by AMC (43%) and TZP (38%). SHV-5 producing K. pneumoniae strains showed the most pronounced inoculum effect with CAZ/cl and AMC and to lesser extent with TZP. Inoculum effect was observed for AMC, CAZ/cl and TZP in 71% of SHV-12 producers. E. coli producing SHV-5 ß-lactamase showed the most pronounced inoculum effect with AMC, followed by CAZ/cl and TZP. Strains producing CTX-M ß-lactamases had a marked inoculum effect with CAZ/cl, AMC and TZP. Carbapenems did not show inoculum effect with any type of ESBLs. Conclusion According to the results of this study, carbapenems remain the antibiotics of choice for the treatment of infections caused by ESBL-producing Enterobacteriaceae. [ABSTRACT FROM AUTHOR]