Determination of extended spectrum β-lactamase-producing Enterobacteriaceae in raw water buffalo milk and dairy products by conventional multiplex and real-time PCR

Abstract

The prevalence of extended spectrum β-lactamase- (ESBL-) producing Enterobacteriaceae from water buffalo milk and its products, as well as genes encoding β-lactam resistance, was determined in a total of 50 raw milk samples and 120 water buffalo milk based dairy products (40 cheese, 40 cream, 30 yoghurt and 10 ice cream samples). A chromogenic-based culture method was used for isolation. Identification of strains was performed with PCR and VITEK MS. The presence of resistance genes was investigated using conventional multiplex and real-time PCR. Of the milk, cheese, yoghurt and cream samples, 26%, 17.5%, 16.6% and 12.5%, respectively, were found to contain at least one ESBL-producing Enterobacteriaceae strain; all ice cream samples were negative in terms of ESBL-producing Enterobacteriaceae. ESBL production of Enterobacter cloacae and Citrobacter freundii strains was found related to blaCTX-M gene. Four Escherichia coli isolates were found containing blaKPC gene with the coexistence of blaCTX-M and/or blaTEM.