Antimicrobial susceptibility and genetic similarity of ESBL-positive Klebsiella pneumoniae strains

Introduction: Twenty-eight isolates of extended-spectrum beta-lactamase (ESBL)-positive Klebsiella pneumoniae were studied. Material and methods: The strains were cultured from different clinical specimens obtained from children hospitalised at the University Hospital in Bydgoszcz. Seventeen strains were isolated from colonization and eleven from clinical infection. Isolation and identification of bacteria were performed using routine methods at the clinical microbiology laboratory. Production of ESBL was assessed using the double disk synergy test. The susceptibility to imipenem and tigecycline was tested by the Etest. The susceptibility to gentamicin and ciprofloxacin was tested by the agar dilution method. The genomic DNA was extracted from the strains separated by pulsed-field gel electrophoresis (PFGE) after digesting with Xbal endonuclease. Results: Among analysed K. pneumoniae strains all were susceptible to imipenem, 21(75.0%) were susceptible to tigecycline, 14 (50.0%) to gentamicin and 5(17.9%) to ciprofloxacin. Molecular typing results revealed a great genetic diversity among K. pneumoniae isolates. All repeated PFGE patterns were detected in seven K. pneumoniae isolates. Among identical K. pneumoniae strains four susceptibility patterns were detected. Conclusions: The results of the study suggest that establishing strains' similarity in epidemiological investigations should be based on results obtained by several methods, and that each phenotyping method should be complemented with genetic research.