A study published in Frontiers in Veterinary Science has found high levels of antimicrobial-resistant (AMR), non-typhoidal Salmonella (NTS) in Vietnamese retail pork. The study also demonstrated the emergence of colistin resistance in NTS in pork, which poses a public health risk considering that colistin is a “last defense” antibiotic that is used against multi-drug-resistant (MDR) pathogens. 

According to the study, pork accounts for 70 percent of meat consumption in Vietnam, and Vietnamese pork has historically high levels of Salmonella contamination. Additionally, AMR within NTS has been a growing issue. 

Using whole genome sequencing (WGS), the study investigated the levels of AMR in 69 NTS isolates that were collected from pork retail outlets and slaughterhouses in Vietnam during 2014 and 2018–2019. Specifically, the study examined whether retail outlet type had an effect on AMR levels in NTS. 

The study identified 17 Salmonella serotypes. S. Typhimurium was most common, followed by S. Rissen, S. London, S. Anatum, and S. Derby. The AMR phenotype was identified in 59.4 percent of isolates that were deemed MDR. 

MDR strains were most common in slaughterhouses (83.3 percent) and supermarkets (71.4 percent), but were least common in traditional markets (38 percent) and convenience stores (40 percent). Colistin resistance was identified in 18 strains. High levels of resistance to the antibiotics ampicillin, tetracycline, chloramphenicol, and trimethoprim were also identified in over half of the isolates.

The study highlights that boutique retail outlets—which market quality, traceable, and environmentally-responsible pork products to high-income consumers—had very high levels of MDR NTS isolates (60 percent). The study emphasizes the importance of addressing AMR in NTS in retail meat, which continues to be a concern despite the improvements that have been made in modern retail.