Abstract:
Background: Klebsiella pneumoniae strains expressing ESBLs are a predominant cause of hospital acquired
infections. Here we describe the molecular epidemiology of these isolates in a tertiary hospital in Tanzania, as
potential pathogens for neonatal infections.
Methods: Between April 2009 and March 2010 all Klebsiella pneumoniae isolates with phenotypic expression
Extended Spectrum Beta Lactamase (ESBL) were collected and characterized. Identification was done using in house
biochemical tests in case of ambiguous results confirmation was done using API 20E. Susceptibility testing was
determined 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 PFGE
clusters representative isolates were performed to determine clones of the isolates. Conjugation and hybridization
were 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 pneumoniae
isolates were characterized. These isolates were from blood 61 (66%), wound swab 13 (14%), urine 12 (13%) and
pus 6 (7%) were analyzed. Most blood culture strains originated from neonatal unit 39/61(64%) and 22 (36%) of the
blood culture isolates were from neonatal ICU. All isolates were resistant to gentamicin and 54% were resistant to
ciprofloxacin. Using a similarity index of 80%, the isolates were assigned to thirteen clusters based on PFGE patterns
and contained sub-clusters with identical strains indicating clonal outbreaks. Cluster X5, X7 and X8, and X9 were
grouped into ST48, ST14 and ST348 respectively. Based on gyrA PCR- RFLP phylogenetic analysis all isolates were
grouped as KpI. The predominant ESBL allele detected was blaCTX-M-15 which was found in 76% of isolates, followed
by blaTEM-104 (19%), blaSHV-11 (3.2%) and blaTEM-176 (2%). The blaCTX-M-15 gene was located in multiple conjugative
IncF 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, is
possibly due to the spread of a common IncFII 145 kb plasmid and of certain clones such as ST14 and ST48.
Furthermore the 485 kb plasmid detected is the largest plasmid reported to carry blaCTX-M-15 todate.
