Research – First report on the molecular characterization and the occurrence of extended-spectrum β-lactamase producing Enterobacteriaceae in unpasteurized bovine’s buttermilk

Wiley Online

The dairy products have been reported as a source of extended-spectrum β-lactamase (ESBL)-producing bacteria. The aim of this study is to determine the potential transfer of ESBL Enterobacteriaceae to humans due to the consumption of buttermilk made from raw, unpasteurized milk collected in Batna province (Northeast of Algeria) as well as to identify isolates and genes encoding resistance in these isolates. Two hundred and forty-three samples of buttermilk made from raw, unpasteurized milk were collected and screened for the presence of ceftazidime-resistant Enterobacteriaceae. The suspected isolates were identified by molecular methods. Enterobacteriaceae isolates were subjected to antimicrobial susceptibility testing and were examined phenotypically for ESBL production and confirmed by using PCR assay and DNA sequencing. Thirteen ceftazidime-resistant Enterobacteriaceae were observed at a rate of 5.76% including Escherichia coli (n = 4), Klebsiella pneumoniae (n = 4), Klebsiella oxytoca (n = 1), Hafnia paralvei (n = 3), and Citrobacter freundii (n = 1). Eight Enterobacteriaceae (61.53%, 8) revealed multidrug resistance, while (61.53%, 8) were confirmed as ESBL-producing Enterobacteriaceae. Polymerase chain reaction assay revealed that blaTEM (87.5%, 7) was the most common gene, followed by the blaCTX-M gene (75%, 6) and finally the blaSHV gene (50%, 4). The sequencing of genes identified blaTEM-1DblaSHV-1, and blaSHV-11. Our findings signified that buttermilk made from raw, unpasteurized milk could be the reservoir for the prevalence of ESBL-producing Enterobacteriaceae and the potential source of transmission for the consumer. Pasteurization of buttermilk is critical to reduce the risk associated with ESBL-producing isolates.

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