Neonatal septicaemia caused by diverse clones of Klebsiella pneumoniae & Escherichia coli harbouring blaCTX-M-15

Background & objectives: Information about the genetic diversity of the extended-spectrum beta-lactamases (ESBLs) and the clonal relationship of the organisms causing neonatal infections is limited, particularly from India where neonatal mortality is high. This study was undertaken to investigate the molecular epidemiology and risk factors associated with neonatal septicaemia caused by ESBL-producing Klebsiella pneumoniae and Escherichia coli. Methods: Bloodstream isolates (n=26) of K. pneumoniae (n=10) and E. coli (n=16) from the neonates admitted in a tertiary care hospital in New Delhi during January to May 2008 were characterized. Antimicrobial susceptibility tests were carried out and ESBL production was assessed phenotypically. PCR was carried out for ESBL and ampC genes. Genotyping was performed by pulsed-field gel electrophoresis (PFGE). Conjugation experiments were done to determine the mobility of ESBL genes. Risk factors associated with ESBL-producing K. pneumoniae and E. coli infections were analysed. Results: Resistance rates to most of the antibiotics tested were high, except for imipenem. Among the isolates tested, 60 per cent of K. pneumoniae and 75 per cent of E. coli were ESBL producers. PFGE of the isolates demonstrated a vast diversity of genotypes with no epidemic clones. Despite the clonal diversity, bla(CTX-M-15) was detected in 100 per cent of ESBL-positive isolates. The other genes present in ESBL-positive isolates were bla(TEM-1), bla(SHV-1), bla(SHV-28), bla(SHV-11), and bla(SHV-12). Class 1 integrons were detected in 7 of 18 ESBL-positive isolates. Moreover, the plasmid carrying bla(CTX-M-15), in E. coli and K. pneumoniae were self transferable. Feeding through an enteral tube was identified as the only risk factor for sepsis by ESBL-producing organisms. Interpretation & conclusions: The study emphasises the presence of bla(CTX-M-15) in clonally diverse isolates indicating probable horizontal transfer of this gene. The widespread dissemination of CTX-M-15 is of great concern as it further confines the limited therapeutic interventions available for neonates.