Staphylococcus aureus contamination in traditional buffalo milk supply chain in Bangladesh

The water buffalo population in Bangladesh has increased over the decades, but the milk supply chain infrastructure is still unregulated and poorly controlled. This increases the risk of spreading opportunistic pathogens like S. aureus, a significant public health concern due to its antibiotic resistance and biofilm formation, which shields it from treatment and promotes persistent infection. The present study estimates the prevalence of Staphylococcus aureus, its antimicrobial resistance, and biofilm-forming ability across Bangladesh's water buffalo milk chain. In addition, risk factors associated with S. aureus were also investigated. One hundred and thirty-two milk samples were collected from three different nodes of the milk supply chain: farm (n = 45), middlemen (n = 42), and collection center (n = 45) from two different farming systems (semi-free-range and smallholder). Thirty (22%) S. aureus isolates from the milk supply chain were confirmed by MALDI-TOF, where the highest number of isolates (n = 12) were identified at the milk collection center than the farm (n = 7) and middlemen (n = 11). All isolates were identified as biofilm producers. The highest number of biofilm producers were observed in the milk collection centers (n = 12). The antimicrobial resistance was found to be highest for ampicillin at 87% (n = 26), followed by penicillin at 83% (n = 25) and erythromycin at 67% (n = 20) respectively. Eight isolates (27%) were considered as multidrug-resistant (MDR). Cleanliness of the milk container at the farm level was associated with S. aureus (p = 0.012) at Fishers' exact test. However, no other variable was found to have a significant association with S. aureus at univariable analysis. In conclusion, the study indicates a high occurrence of resistance and biofilm-producing S. aureus along the buffalo milk supply chain. Implementing a proper supply chain and determining some critical control points are required to attain consumer safety and reduce S. aureus contamination.