Molecular characterisation of extended spectrum beta-lactamases producing Enterobacteriaceae
Abstract
Extended Spectrum beta-lactamase producing Enterobacteriaceae have been
responsible for numerous outbreaks of infections worldwide. Escherichia coli and
Klebsiella pneumoniae species are the main producers of ESBLs, causing hospital and
community acquired infections. The aim of this study was to isolate and identify ESBL
producing Enterobacteriaceae from cattle faeces and raw beef samples and determine
the presence of ESBL determinants using specific PCR assays. A total of 151 samples
were analysed and 259 presumptive isolates screened for characteristics of
Enterobacteriaceae using biochemical tests and 16S rRNA universal gene. A total of
196 isolates were confirmed as E. coli and K. pneumoniae through amplification of uidA,
uspA and ntrA genes fragments respectively. Antimicrobial susceptibility test was
performed to determine antibiotic resistance profiles of the isolates. Large proportions
(66.7-100%) of isolates were resistant to Amoxicillin, Aztreonam, Ceftazidime,
Cefotaxime and Piperacillin.
Correlations between antibiotic resistant isolates from the various sources was
determined using the Pearson's product of moment and scored as significant if P≤0.05.
Phenotypic characterisation by cluster analysis of antibiotic inhibition zone diameter
data used to determine the commonness of isolates and resolve the differences of
isolates from various sources and/or locations revealed a close association between
isolates derived from cattle faeces and beef samples. This implies that the isolates may
have originated from the common progeny.
A total of 196 isolates were screened for the presence of ESBL determinants. Among all
the isolates analysed, the prevalence of ESBL was 53.1%. The blaTEM, blaSHV and
blaCTX-M genes were detected in 85.5%, 69.6% and 58% of the isolates respectively and
this was most prevalent among E. coli isolates. Similarly, the blaCTX-M gene was the
most frequently detected in K. pneumoniae isolates. On the contrary, blaOXA gene was
highly prevalent in K. pneumoniae. The genetic relatedness of the isolates was
determined using ERIC PCR technique. The DNA fragments showed great similarities
in the banding patterns among E. coli and K. pneumoniae isolates. From the findings of
this study, there is a need for continuous monitoring of ESBL producing strains in food
products and food producing animals.