Spreading and Mechanisms of Antimicrobial Resistance in Microorganisms, Producing Beta-Lactamases.Molecular Mechanisms of Resistanceto Beta-Lactam Antibiotics of Klebsiella spp. Strains,Isolated in Cases of Nosocomial Infections

摘要

Antibiotic sensitivity has been investigated in nosocomial bacterial Klebsiella spp. strains isolatedfrom patients treated in 30 hospitals of 15 Russian regions. Among Klebsiella strains (n = 212) studied the fol-lowing species were found: Klebsiella pneumoniae ss. pneumoniae-182 (85.8%), Klebsiella pneumoniae ss.ozaenae-1 (0.5%), Klebsiella oxytoca-29 (13.7%) strains. Their sensitivity to antibacterial preparations wasestimated by the method of serial dilutions in microvolume (the microdilution method). Carbapenems (imi-penem and meropenem) exhibited the highest antibacterial activity against the strains studied. Among third gen-eration cephalosporins the lowest MIC (Minimum inhibitory concentration) were found in the inhibitor pro-tected preparations: ceftazidime/clavulanic acid (MIC_(50)of 0.25 μg/ml; MICK, of 64 μg/ml) and cefopera-zone/sulbactam (MIC_(50)of 16 μg/ml; MIC_(90)64 μg/ml). Using the PCR method the detection of class A beta-lactamases genes (TEM, SHV, CTX) was carried out in 42 strains of Klebsiella pneumoniae ss. pneumoniae.TEM type beta-lactamases were found alone or in various combinations in 16 (38.1%) strains, SHV—in 29(69%), and CTX—in 27 (64.3%). Combinations of 2 and 3 different resistance determinants were detected in23.8 and 26.2% of strains, respectively. Screening of carbapenem-resistant Klebsiella strains for production ofclass B metallo-beta-lactamases did not reveal nosocomial strains with phenotypically documented productionof these enzymes.