Isolation and molecular detection of enterotoxigenic Staphylococcus aureus from raw milk of cows

Abstract

Staphylococcus aureus is a microbe associated with human’s food poisoning. It is caused by isolates producing different heat stable enterotoxins which act as one of the most spread worldwide gastroenteritis causes. The goal of the current study was to assess the incidence of S. aureus (enterotoxigenic) in the raw milk samples of cows which were collected from various places of Baghdad city. Isolation and identification of S. aureus were done by conventional laboratory method and the diagnoses were confirmed by using molecular method RT-PCR to detect the specific gene of S. aureus nuc gene. In addition, we investigate the occurrence of some of Staphylococcal enterotoxins genes such as SEA, SEB, SEC, SED, and SEE. We found that 12/50 (24%) of the isolates were S. aureus and these isolates carried one or more of the enterotoxin genes such as enterotoxin type SEC 12/12 (100) followed by enterotoxin type SEA 7/12 (58.33%) and only 1/12 (8.33%) was type SED, while type SEB and SEE were negative 0%. Some of the isolates have genes that coded for two enterotoxins patterns such as SEA and SEC 7/12 (58.33%) and SEC and SED 1/12 (8.33%). Fewer of the isolates expressed only one genotype of enterotoxin gene like SEC 4/12 (33.3%). This study has proven that there was a high chance of occurrence for the enterotoxigenic S. aureus at the raw milk of cows in Baghdad city.

Keywords

• enterotoxins genes
• nuc gene
• raw milk
• rt-pcr
• s. aureus