CTX-M Type Beta-Lactamase Frequency and Antibiotic Co-resistance in Extended Spectrum Beta-Lactamase Producing Klebsiella pneumoniae Strains

Objective: Extended spectrum beta-lactamase-producing Klebsiella pneumoniae infections cause difficulties in antibiotic choice for treatment. In this study, the frequency of CTX-M type beta-lactamase, antibiotic resistance rates and co-resistance rates in extended spectrum beta-lactamase (ESBL)-producing K. pneumoniae strains isolated in our hospital were investigated. Material and Methods: A total of 107 K. pneumoniae strains isolated from various clinical specimens in 2007 were included in the study. Antibiotic susceptibility test was performed using disc diffusion method through the recommendations of Clinical Laboratory Standards Institute (CLSI). Double disk synergy test was used for detection of ESBL production. Carbapenemase production was determined with Modified Hodge test. Presence of the gene belonging to CTX-M type beta-lactamases was investigated with polymerase chain reaction method using primers specific to these sites. Results: Frequency of CTX-M type beta-lactamase was detected as 85%. In general, the isolates were found to be highly resistant to co-trimoxasole (SXT) (79%), ampicillin-sulbactam (SAM) (77%), amoxicillin-clavulanic acid (AMC) (68%) and nitrofurantoin (NIT) (52%), and they were found to be less resistant against amikacin (AK) (19%), ciprofloxacin (CIP) (21%), norfloxacin (NOR) (24%), gentamicin (GN) (31%), cefoperazone-sulbactam (SCF) (32%) and piperacillin-tazobactam (TZP) (37%). While the resistance against meropenem (MEM) and fosfomycine (FOS) which are among the most effective antibiotics was determined as 2% and 3% respectively, no resistance was found agaist imipenem. Co-resistance was detected in 90% of the strains and the most common two co-resistance phenotypes were found as AMC/SAM/SXT/NIT (9%) ye AMC/SAM/SXT (6.5%). Conclusion: CTX-M type beta-lactamases were found to be considerably high in K. pneumoniae strains. It was concluded that empirical treatments with these antibiotics could be insufficient in our region since resistance against SXT, SAM, AMC and NIT is high in ESBL producing K. pneumoniae strains