Resumo

Carbapenem resistance in Enterobacteriaceae is closely related to the production of the enzyme KPC (Klebsiella pneumoniae carbapenemase). However, reports of other mechanisms such as metallo beta-lactamases (MBL), the action of the efflux pumps and changes in the composition of outer membrane porins, may also contribute to the resistence.The objective of this study was to report the unusual phenotype of an isolate of Enterobacter gergoviae showing positive phenotypic test for MBL production and the presence of blaKPC gene. The strain of Enterobacter gergoviae was obtained from urine culture. The minimum inhibitory concentration (MIC) was performed by broth microdilution according to CLSI (2010). The antimicrobial agents used were gentamicin (GEN), tigecycline (TIG), ceftazidime (CAZ), ceftriaxone (CEF), cefotaxime (CTX), cephalothin (CFL), ciprofloxacin (CIP), piperacillin / tazobactam (PPT), amoxicillin / clavulanate (AMC), aztreonam (ATM), imipenem (IMP), meropenem (MER), cefepime (CPM) and polymyxin (POLB). The isolate was tested phenotypically for ESBL (extended spectrum beta-lactamase), MBL and KPC production using double-disk synergy (ESBL and MBL) and Hodge test (modified). Genomic DNA of the bacterial isolate was extracted by the method of Brazol® and blaKPC and Intl genes were investigated by specific PCR. The isolate showed resistance to cephalosporins (CAZ - MIC 128 µg/mL, CTX – MIC> 256 µg/mL, CEF-MIC > 64 µg/mL ,CFL-MIC >256 µg/mL, CPM – MIC >512 µg/mL) and aztreonam (ATM - MIC> 128 µg/mL). For carbapenems, the strain was resistant to imipenem (MIC 64 ug/mL) and meropenem (MIC 32 ug/ml). The isolate showed sensitivity to ciprofloxacin, polymyxin and tigecycline and showing positive phenotypic test for metallo beta-lactamase and blaKPC gene. Investigation of metallo beta-lactamases and ESBL genes will be performed. This fact alerts to the potential risk of accumulation of different enzymatic carpabenem resistance mechanisms which could lead to the emergence of isolates highly efficient to resist to antimicrobials and contribute to the failure in the antibiotic therapy applied to patient.