Isolation and Molecular Characterization of Enterotoxigenic Strains of Staphylococcus aureus in Raw Milk from District Kasur, Punjab, Pakistan

Abstract

This research aimed to isolate and molecularly characterize Staphylococcus aureus (S. aureus) from raw milk. We collected 600 raw milk samples from commercial dairy farms, milk collection centers, and Gawalas (200 samples each) in Kasur District, Punjab, Pakistan. S. aureus was identified in 270 (45%) of the samples using culture techniques. Raw milk from Gawalas had the highest prevalence, with 110 (55%) positive samples, followed by 90 (45%) from milk collection centers and 70 (35%) from commercial dairy farms. The S. aureus isolates that tested positive for enterotoxin genes were further characterized using PCR. In raw milk from commercial dairy farms, the enterotoxin C gene was detected in 42.86% of samples, while the A and B genes were present in 28.57% each. In raw milk from collection centers, the enterotoxin A gene was found in 42.86% of samples, and the B and C genes in 28.57% each. In Gawala's raw milk, the enterotoxin A gene was present in 50% of samples, while the B and C genes were present in 30% and 20% of samples, respectively. Overall, enterotoxin genes A, B, and C were identified in 41.67%, 29.17%, and 29.17% of the samples, respectively. This study found a significant incidence of enterotoxigenic S. aureus in raw milk from Gawlas, indicating that unsanitary milking practices increase the risk of milk-borne diseases, and recommends implementing pasteurization.