Pilot Monitoring of Antimicrobial Residues in Chicken and Pork in Vietnam.

ABSTRACT: Antibiotic residues in consumer foods pose a threat to human health and contribute to increasing antimicrobial resistance. The study was conducted from January to July 2019 in six provinces in Vietnam. In total, 360 pork samples and 360 chicken samples were collected for analysis. The samples were first screened with an enzyme-linked immunosorbent assay test kit for residues in the beta-lactam, tetracycline, and sulfonamide groups. All positive and suspected positive samples were confirmed by liquid chromatography-tandem mass spectrometry to determine the concentration of ampicillin, amoxicillin, sulfamethazine, sulfaquinoxaline, oxytetracycline, and doxycycline residues. The final confirmed result showed that 13 (3.6%), 99 (27.5%), and 16 (4.4%) chicken samples and 13 (3.6%), 29 (8.1%), and 29 (8.1%) pork samples were positive or suspected positive with beta-lactam, tetracycline, and sulfonamide residues, respectively. The liquid chromatography-tandem mass spectrometry method detected amoxicillin (8.1 to 151.6 ng/g), ampicillin (1.9 to 7.5 ng/g), doxycycline (1.1 to 491.1 ng/g), oxytetracycline (1.1 to 12.9 ng/g), sulfaquinoxaline (1.1 to 7.3 ng/g), and sulfamethazine (1.0 to 1,556.5 ng/g) in positive or suspected positive pork and chicken samples. Tetracycline (18%) was the most frequently found residue, followed by sulfonamide (6%). The proportion of chicken samples with a residue level higher than the maximum residue limit (3%) and the level of tetracycline residue were significantly higher than pork (1%). A significantly higher proportion of samples with residue levels higher than MRL (4%) and the highest levels of tetracycline residue were observed in north Vietnam. This data can help motivate decision-making toward lowering the use of antimicrobials in livestock and antibiotic residue in livestock products.

Antimicrobial residues, non-typhoidal Salmonella, Vibrio spp. and associated microbiological hazards in retail shrimps purchased in Ho Chi Minh city (Vietnam).

We investigated antimicrobial residues, non-typhoidal Salmonella (NTS), Vibrio spp. and their associated antimicrobial resistance (AMR), in shrimps locally purchased in Ho Chi Minh City (Vietnam). In addition, we investigated the relationship between AMR in NTS, Vibrio spp. and antimicrobial residue in the same sample. A total of 40 samples of shrimp heads/shells from different retail sources was cultured using ISO 6579-1:2017 (NTS) and ISO/TS 21872-1:2007 (Vibrio spp.). Phenotypic antimicrobial susceptibility was investigated using Vitek (NTS, 34 antimicrobials) and disk diffusion (Vibrio spp., 12 antimicrobials). A total of 9 (22.5%) samples contained antimicrobial residue, including tetracyclines, fluoroquinolones, sulfonamides and macrolides (in 7.5%, 7.5%, 2.5% and 2.5% of samples, respectively). Shrimp samples from supermarkets had a higher prevalence of antimicrobial residue than those purchased in street markets (50% vs. 13.3%) (p = 0.049). A total of 30 (75%) samples were contaminated with NTS. All samples contained Vibrio spp., with V. parahaemolyticus being most common (87.5% samples). A total of 58.9% NTS isolates were multidrug resistant. With regards to the highest priority, critically important antimicrobials, the highest resistance corresponded to quinolones (14.4-47.8%), followed by 3rd and 4th generation cephalosporins (3.3-7.8%). Vibrio spp. isolates were characterised by their high resistance against ampicillin (82.7%) and 3rd generation cephalosporins (8.3-16.5%). Extended Spectrum Beta-Lactamase (ESBL) activity was detected in 28.1% V. parahaemolyticus isolates. Half of ESBL-positive V. parahaemolyticus strains harboured bla CTX-M1. We found an association between the presence of residues and the number of resistances for NTS (p = 0.075) and Vibrio spp. isolates (p = 0.093) from the same sample. These findings suggest that the presence of residues may contribute to the selection of AMR in foodborne pathogens in shrimps. Authorities should strengthen policies aiming at restricting inappropriate antimicrobial usage in shrimp farming, and step up monitoring of antimicrobial residues and food-borne pathogens at retail in Vietnam.