Predominance of Klebsiella pneumoniae ST14 carrying CTX-M-15 causing neonatal sepsis in Tanzania

Abstract

Background: Klebsiella pneumoniae strains expressing ESBLs are a predominant cause of hospital acquiredinfections. Here we describe the molecular epidemiology of these isolates in a tertiary hospital in Tanzania, aspotential pathogens for neonatal infections.Methods: Between April 2009 and March 2010 all Klebsiella pneumoniae isolates with phenotypic expressionExtended Spectrum Beta Lactamase (ESBL) were collected and characterized. Identification was done using in housebiochemical tests in case of ambiguous results confirmation was done using API 20E. Susceptibility testing wasdetermined using the disc diffusion method followed by specific PCR and sequencing to determine ESBL genes.Phylogenetic analysis, Pulse field gel electrophoresis (PFGE) and Multi-Locus sequence typing (MLST) to PFGEclusters representative isolates were performed to determine clones of the isolates. Conjugation and hybridizationwere performed to determine the location of blaCTX-M-15 gene.Results: A total of 92 non- repetitive ESBL producing K. pneumoniae representing 50.3% of Klebsiella pneumoniaeisolates were characterized. These isolates were from blood 61 (66%), wound swab 13 (14%), urine 12 (13%) andpus 6 (7%) were analyzed. Most blood culture strains originated from neonatal unit 39/61(64%) and 22 (36%) of theblood culture isolates were from neonatal ICU. All isolates were resistant to gentamicin and 54% were resistant tociprofloxacin. Using a similarity index of 80%, the isolates were assigned to thirteen clusters based on PFGE patternsand contained sub-clusters with identical strains indicating clonal outbreaks. Cluster X5, X7 and X8, and X9 weregrouped into ST48, ST14 and ST348 respectively. Based on gyrA PCR- RFLP phylogenetic analysis all isolates weregrouped as KpI. The predominant ESBL allele detected was blaCTX-M-15 which was found in 76% of isolates, followedby blaTEM-104 (19%), blaSHV-11 (3.2%) and blaTEM-176 (2%). The blaCTX-M-15 gene was located in multiple conjugativeIncF plasmids ranging from 25 kb-485 kb in size.Conclusion: The high prevalence of blaCTX-M-15 observed among ESBL producing K. pneumoniae in Tanzania, ispossibly due to the spread of a common IncFII 145 kb plasmid and of certain clones such as ST14 and ST48.