Contamination and antimicrobial resistance testing of Staphylococcus aureus isolates from pork in the traditional market at Central Vietnam.

BACKGROUND

Staphylococcus aureus is an opportunistic pathogen widely present in humans and food-producing animals. The emergence of antimicrobial resistance (AMR) in S. aureus represents a major challenge for both animal and public health.

AIM: This study investigated the presence of S. aureus in pork sold in traditional markets in Central Vietnam, analyzing its AMR profile and evaluating potential public health risks.

METHODS

We collected 48 retail pork samples from traditional markets in Central Vietnam. The S. aureus count (log10 CFU/g) was determined using Baird-Parker (BP) medium and was confirmed by the coagulase reaction. The S. aureus isolates were tested for AMR and AMR genes (ARGs) using the disk diffusion method and PCR, respectively.

RESULTS

All 48 retail pork samples (100%) tested positive for S. aureus, with S. aureus counts ranging from 4.17 to 4.52 log10 CFU/g. AMR was most commonly observed against penicillin (75.0%), followed by amoxicillin (64.6%), tetracycline (54.2%), ampicillin (41.7%), neomycin (39.6%), and vancomycin (39.6%). Multidrug resistance was observed in 85.4% of the S. aureus isolates, with penicillin-ampicillin-amoxicillin being the most common resistance pattern. The highest frequency of S. aureus isolates carried the tetM (30/48, 62.5%) gene, followed by blaZ (25/48, 52.1%), and femA (20/48, 41.7%). Moreover, the results revealed a positive correlation among β-lactams, specifically between ampicillin and neomycin, and between amoxicillin and erythromycin/neomycin.

CONCLUSION

The high AMR of S. aureus isolates from retail pork samples is alarming and raises public health concerns. Food of animal origin serves as a source of AMR S. aureus, which can spread throughout the food supply chain. Therefore, controlling S. aureus requires targeting specific entry points based on findings related to risk factors and food contamination drivers.