Distribution of bacteria and antimicrobial resistance in retail Nile tilapia (Oreochromis spp.) as potential sources of foodborne illness

PLoS One. 2024 Apr 2;19(4):e0299987. doi: 10.1371/journal.pone.0299987. eCollection 2024.

Abstract

This study aimed to investigate AMR profiles of Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae isolated from Nile tilapia (Oreochromis spp.) (n = 276) purchased from fresh markets and supermarkets in Bangkok, Thailand. A sample of tilapia was divided into three parts: fish intestine (n = 276), fish meat (n = 276), and liver and kidney (n = 276). The occurrence of A. hydrophila, Salmonella, and V. cholerae was 3.1%, 7.4%, and 8.5%, respectively. A high prevalence of these pathogenic bacteria was observed in fresh market tilapia compared to those from supermarkets (p < 0.05). The predominant Salmonella serovars were Paratyphi B (6.4%), followed by Escanaba (5.7%), and Saintpaul (5.7%). All isolates tested positive for the virulence genes of A. hydrophila (aero and hly), Salmonella (invA), and V. cholerae (hlyA). A. hydrophila (65.4%), Salmonella (31.2%), and V. cholerae (2.9%) showed multidrug resistant isolates. All A. hydrophila isolates (n = 26) exhibited resistant to ampicillin (100.0%) and florfenicol (100.0%), and often carried sul1 (53.8%) and tetA (50.0%). Salmonella isolates were primarily resistant to ampicillin (36.9%), with a high incidence of blaTEM (26.2%) and qnrS (25.5%). For V. cholerae isolates, resistance was observed against ampicillin (48.6%), and they commonly carried qnrS (24.3%) and tetA (22.9%). To identify mutations in the quinolone resistance determining regions (QRDRs), a single C248A point mutation of C248A (Ser-83-Tyr) in the gyrA region was identified in six out of seven isolates of Salmonella isolates. This study highlighted the presence of antimicrobial-resistant pathogenic bacteria in Nile tilapia at a selling point. It is important to rigorously implement strategies for AMR control and prevention.

MeSH terms

  • Aeromonas hydrophila / genetics
  • Ampicillin
  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Cichlids* / microbiology
  • Drug Resistance, Bacterial / genetics
  • Foodborne Diseases* / epidemiology
  • Salmonella
  • Thailand / epidemiology

Substances

  • Anti-Bacterial Agents
  • Ampicillin

Grants and funding

This study was supported by Thailand Science Research and Innovation Fund Chulalongkorn University (HEA663100108), National Research Council of Thailand (NTCT) (N42A660897), University of California Davis (A22-3754-S001), and Rachadapisek Sompote Fund Chulalongkorn University (GR_62_37_31_02) and College of Industrial Technology, King Mongkut’s University of Technology North Bangkok (Res-CIT0232/2019). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.