Resumo

Klebsiella pneumoniae carbapenemase (KPC) is an enzyme produced by Gram-negative bacteria capable of conferring resistance to all beta-lactams including carbapenems. For this reason, polymyxin B has often been regarded as the last choice in the treatment of infections caused by Klebsiella pneumoniae.However, changes in bacterial outer membrane may lead to the development of resistance to this drug, resulting in isolates with no therapeutic options. The aim of this study was to report an isolate of K. pneumoniae positive for KPC production that developed resistance to a wide range of antibiotics, including polymyxin B during treatment in the ICU of a public hospital in Recife. Between September and October 2013, two K. pneumoniae isolates were recovered from the cerebrospinal fluid (CSF) of a 37 years old patient. The modified Hodge test and ethylenediaminetetraacetic acid (EDTA) and mercaptopropionic acid (2-AMP) inhibition test were used to verify the presence of KPC and metallo-beta-lactamase (MBLs), respectively. Antimicrobial susceptibility was determined by automated Vitek-2 and E-test, following the Clinical and Laboratory Standards Institute (CLSI, 2013) breakpoints. The detection of blaKPC gene was performed by PCR. Clonal relatedness of the isolates was verified by pulsed-field gel electrophoresis (PFGE). The results showed that the two isolates were resistant to all the antimicrobial agents tested except amikacin and gentamicin. It was observed that both isolates were positive for Hodge test and had the blaKPC gene. EDTA phenotypic test was positive for MBL production on the two isolates. Molecular typing showed that the isolates were indistinguishable. It was observed that the first isolate (KPC1) was susceptible to polymyxin B (MIC = 1,5 µg/ml) while the second one (KPC2) showed resistance to this drug (MIC = 12 µg/ml) after 1 moth interval, indicating that the resistance to this drug may have arisen in vivo by antimicrobial therapy selective pressure. These findings indicate the need for improved infection control measures in the hospital analyzed related to the clonal spread of multiresistant isolates, and alert to the potential of these isolates to also acquire resistance to polymyxin B, considered as a last choice drug in the treatment of serious infections caused by enterobacteria.