Serotypes, Virulence Genes, and Intimin Types of Shiga Toxin-ProducingEscherichia coliand EnteropathogenicEscherichia coliIsolated from Mastitic Milk Relevant to Human Health in Egypt

Abstract

Some foodborne pathogens can cause mastitis, in which the organism is directly excreted into milk. Therefore, we undertook the steps to determine the prevalence and molecular characteristics of Shiga toxin-producing Escherichia coli (STEC) isolates from bovine mastitic milk in Egypt. Forty milk samples from dairy cattle showing mastitis were collected and examined for the presence of E. coli. Following enrichment and plating on selective agar, confirmation of the isolates was based on biochemical tests and the isolates were determined at the species level using cytochrome oxidase, triple sugar iron agar, urea, and indole tests as putatively E. coli. About 77.4% of the isolates belonged to four different O serogroups (O26, O86, O111, and O127). The multiplex polymerase chain reaction (PCR) found that the seven isolates revealed positive amplification of the Eagg gene from the extracted DNA of the E. coli isolates in an incidence of 100%. Also, the selected isolates were subjected to a simple PCR for the detection of 12 of the most important E. coli genes associated with virulence. Those genes detected were stx1, stx2, hylA, Flic(h7), stb, F41, K99, sta, F17, LT-I, LT-II, and eaeA. A total of seven E. coli isolates that were non-O157 isolates were investigated. Among the seven isolates, none was stx positive, and all seven lacked F41, K99, LT-I, LT-II, and Flic(h7). Of these seven isolates, three (42.85%) were enterohemorrhagic E. coli hlyA positive and two (28.57%) were eaeA positive. STEC isolates were not found in bovine mastitic milk in Egypt. Isolates from mastitic milk were potentially pathogenic for human in that they belonged to serogroups associated with diarrhea and hemolytic-uremic syndrome, and some of them were hylA, stb, sta, F17, and eaeA positive.