RESUMEN
Klebsiella pneumoniae which is a causative agent of nosocomial infections, is protected from phagocytosis and the lethal effect of serum bactericidal proteins owing to its capsular polysaccharides (CPS). The important leading problem in treating infections caused by this bacterium that successfully develops antimicrobial resistance, especially via mobile genetic elements, is that it acquires beta-lactamase genes, which are responsible for the resistance against beta-lactam antibiotics. Due to the increase in studies targeting capsular polysaccharides in developing strategies for vaccination and treatment, we aimed to investigate the possible relationship of the capsular genotypes of K.pneumoniae isolates obtained from various clinical specimens with antibiotic susceptibility and beta-lactamase genes. In K.pneumoniae clinical isolates; K1, K2, K5, K20, K54 and K57, which are known as hypervirulent capsular types, were investigated by polymerase chain reaction (PCR) method. In isolates whose capsular genotypes were determined, antibiotic susceptibility was examined by Kirby-Bauer disc diffusion method. Colistin resistance was investigated by the broth microdilution method. Carbapenem resistance was confirmed with the carbapenem inactivation test. The beta-lactamase genes blaCTX-M1, blaCTX-M2, blaCTX-M9, blaCTX-M8/25, blaKPC, blaNDM-1, and blaOXA-48-like were investigated by using PCR. Of the 38 K.pneumoniae isolates whose capsular genotypes were determined, 15 (39.5%), 12 (31.6%), seven (18.4%), two (5.3%), one (2.6%) and one (2.6%) were K5-CPS, K2-CPS, K20-CPS, K1-CPS, K54-CPS and K57-CPS genotypes, respectively. blaOXA-48-like, blaNDM-1, and blaCTX-M1 were detected in 68.4, 10.5, and 7.9%, whereas coexistence of blaOXA-48-like with blaNDM-1, and blaOXA-48-like with blaCTX-M1 were determined in 7.9, and 5.3% of the isolates, respectively. The relationship of the blaCTX-M1 gene, detected only in three K20-CPS isolates, was found to be statistically significant with this genotype. In addition, of the blaNDM-1-positive four isolates, three were K5-CPS, and one was K2-CPS, while blaOXA-48-like was similarly detected mostly in K5-CPS and K2-CPS (10 and 9 isolates, respectively). Except for the two isolates that were resistant to colistin, one K1-CPS and the other K5-CPS, the highest resistance was detected against cefotaxime (36/38) and the lowest resistance was detected against gentamicin (23/38) as a result of antibiotic susceptibility tests. The resistance relationship of K5-CPS isolates with amoxicillin/clavulanate, piperacillin/tazobactam, cefoxitin and ertapenem and the susceptibility relationship of K20-CPs isolates with amoxicillin/clavulanate, piperacillin/tazobactam, imipenem, tetracycline and trimethoprim/sulfamethoxazole were found as statistically significant. Our study is the first to investigate the relationship between K.pneumoniae capsular genotypes and beta-lactamase genes in Turkey. As a result, it is believed that this research will contribute to the determination of vaccine and treatment options by providing data to wider and regional studies that will examine other capsule genotypes and antibiotic resistance genes to clarify the importance of the capsule in virulence.
