Molecular evidence for cross boundary spread of Salmonella spp. in meat sold at retail markets in the middle Mekong basin area

Prevalence of Salmonella spp. in meat, seafood, and leafy green vegetables from local markets and vegetable farms in Phnom Penh, Cambodia

Salmonella is a major bacterial concern for public health globally. Although there are limited documentation on the prevalence of Salmonella species in Cambodia's food chain, some reports indicate that salmonellosis is a severe gastrointestinal infection in its population and especially in children. To investigate the presence of Salmonella spp., 285 food samples (75 meat, 50 seafood, and 160 leafy green vegetable samples) were randomly collected from various local markets in Phnom Penh capital and nearby farms in Cambodia. Concurrently, field observations were conducted to collect data on food hygiene and practices among the relevant actors. All food samples were analyzed using bacterial culture and plate counts, and the findings were confirmed serially with biochemical, serological, and PCR tests. The observational data on food hygiene and practices from farm to market revealed that the spread of Salmonella in the food-value chain from farm to market could pose health risks to consumers. The overall prevalence of Salmonella spp. was 48.4% (138/285), while the prevalence in meat, seafood, and vegetables was 71% (53/75), 64% (32/50), and 33% (53/160), respectively. Mean Salmonella plate count ranged from 1.2 to 7.40 log10 CFU/g, and there was no significant difference in bacterial counts between meat, seafood, and vegetable samples (p > 0.05). The most common serogroups among the isolated Salmonella spp. were B and C. These results suggest that a large proportion of meat, seafood, and vegetable products sold at local markets in Phnom Penh are contaminated with Salmonella spp. This is likely linked to inadequate hygiene and sanitation practices, including handling, storage, and preservation conditions. Observations on farms suggested that the prevalence of Salmonella in vegetables sold at the market could be linked to contamination relating to agricultural practices. Thus, controlling the spread of foodborne salmonellosis through the food-value chain from farms and retailers to consumers is warranted to enhance food safety in Cambodia.

Genomic analysis of Salmonella enterica from Metropolitan Manila abattoirs and markets reveals insights into circulating virulence and antimicrobial resistance genotypes

The integration of next-generation sequencing into the identification and characterization of resistant and virulent strains as well as the routine surveillance of foodborne pathogens such as Salmonella enterica have not yet been accomplished in the Philippines. This study investigated the antimicrobial profiles, virulence, and susceptibility of the 105 S. enterica isolates from swine and chicken samples obtained from slaughterhouses and public wet markets in Metropolitan Manila using whole-genome sequence analysis. Four predominant serovars were identified in genotypic serotyping, namely, Infantis (26.7%), Anatum (19.1%), Rissen (18.1%), and London (13.3%). Phenotypic antimicrobial resistance (AMR) profiling revealed that 65% of the isolates were resistant to at least one antibiotic, 37% were multidrug resistant (MDR), and 57% were extended-spectrum β-lactamase producers. Bioinformatic analysis revealed that isolates had resistance genes and plasmids belonging to the Col and Inc plasmid families that confer resistance against tetracycline (64%), sulfonamide (56%), and streptomycin (56%). Further analyses revealed the presence of 155 virulence genes, 42 of which were serovar-specific. The virulence genes primarily code for host immune system modulators, iron acquisition enzyme complexes, host cell invasion proteins, as well as proteins that allow intracellular and intramacrophage survival. This study showed that virulent MDR S. enterica and several phenotypic and genotypic AMR patterns were present in the food chain. It serves as a foundation to understand the current AMR status in the Philippines food chain and to prompt the creation of preventative measures and efficient treatments against foodborne pathogens.