Abstract

Milk is a substantial source of nutrients needed by all humans across lifespan development. Given its nutritional composition, milk is considered a vehicle for various microbes including beneficial and pathogenic bacteria. In this study, 270 milk samples comprising raw cow and buffalo milk and pasteurized milk with different shelf-life durations were tested along with pasteurized organic milk for the presence of Staphylococcus aureus and Escherichia coli. Collectively, 21 E. coli and 14 S. aureus isolates were cultivated and identified from total milk samples. All E. coli and S. aureus isolates exhibited resistance to erythromycin and penicillin, respectively. Serogroups O26, O128, and O111 were the most frequently identified amongst E. coli isolates, whereas staphylococcal enterotoxins (SEs) were inconsistently produced across S. aureus isolates. The molecular profile showed clustering of 6 isolates of E. coli by harboring stx1, stx2, eaeA genes, and 5 isolates of S. aureus by mecA gene. Findings revealed the bacteriological quality of popularly consumed milk in Egypt, including raw and pasteurized milk with preference to pasteurized organic milk and 7-day shelf life (7DSL) pasteurized milk. However, raw milk and 3MSL pasteurized milk were the major sources of E. coli and S. aureus, posing a serious public health issue.

Key words: Raw milk, pasteurization, Staphylococcus aureus and Escherichia coli, shelf-life.