Epidemic diffusion of Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamases in neonatal and pediatric wards in Rabta hospital of Tunisia

Abstract

Klebsiella pneumoniae producing extended-spectrum β-lactamase (ESBL) cause severe life threatening infections resulting in considerable morbidity and mortality especially in neonatology ward. The aim of this study was to evaluate the epidemiology and resistance of 131 strains collected between 2007 and 2008 in neonatology and pediatric wards and to determine the mode of their epidemic spread. The isolates were identified, tested for antimicrobial susceptibility with the disk-diffusion on Mueller-Hinton agar. The type of ESBL was determined by polymerase chain reaction (PCR) followed by sequencing for CTX-M enzymes. The epidemiological relationships between epidemic strains were analysed by pulsedfield gel electrophoresis. In this study, antibiotic susceptibility testing showed resistance to all β-lactams except imipenem with a concomitant resistance to aminoglycosides, tetracycline and cotrimoxazole. Fluoroquinolones still have activity against strains. Characterization of β-lactamases encoding genes revealed that all strains have SHV β-lactamases. TEM-type and CTX-M-1 group were encoded, respectively, in 21 and 57% of ESBLs isolates. Among 84 strains tested by PFGE, 14 pulsotypes were identified. DNA sequencing of amplified CTX-M β-lactamase genes justified diffusion of CTX-M-15 between epidemic strains. In conclusion, this study revealed a high degree of clonal diversity of isolates and complexity of outbreaks that involve more than two epidemic pulsotypes and indicated that both clonal spread of epidemic strains and transfer of β-lactamases might contribute to epidemic dissemination of ESBL in neonatology ward.