Short communication: Detection of stx2 and elt genes in bovine milk by using a multiplex PCR system

The aim of this study was to detect 2 important toxin genes from diarrheagenic Escherichia coli (DEC) in bovine milk using a new multiplex PCR. To standardize the multiplex PCR, the stx2 and elt genes were investigated for the detection of Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC), respectively. The DNA template was prepared with a thermal procedure (boiling) and a commercial kit. Samples consisted of UHT and pasteurized milk, both skimmed, and STEC and ETEC were tested in concentrations between 10¹ and 10⁹ cfu/mL. With the thermal procedure, the multiplex PCR system detected both pathotypes of E. coli at 10⁹ cfu/mL in UHT and pasteurized milk. When the commercial kit was used for template preparation, STEC and ETEC could be detected at concentrations as low as 10⁴ cfu/mL in UHT and pasteurized milk. Negative controls (Listeria monocytogenes, Salmonella Typhimurium, Salmonella Enteritidis, and Escherichia coli strain APEC 13) were not amplified with the multiplex PCR. These results indicate that the multiplex PCR was a rapid (less than 6 h) and efficient method to detect STEC and ETEC in milk using different methods for DNA preparation; however, the commercial kit was more sensitive than the thermal procedure.