Wide distribution of plasmid mediated quinolone resistance gene, qnrS, among Salmonella spp. isolated from canal water in Thailand.

AIMS: This research focused on assessing the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and antimicrobial susceptibility in Salmonella strains isolated from Thai canal water. METHODS AND RESULTS: From 2016 to 2020, 333 water samples were collected from six canals across Bangkok, Thailand. Salmonella spp. was isolated, PMQR genes were detected through polymerase chain reactions, and the antimicrobial susceptibility was examined using the disk diffusion method. The results indicated a 92.2% prevalence of Salmonella spp. in canal water, being serogroups B and C the most frequently detected. Overall, 35.3% of isolates harbored PMQR genes, being qnrS the most prevalent gene (97.2%, n = 137/141). Other PMQR genes, including qnrB, qnrD, oqxAB, and aac(6')-Ib-cr, were detected. Notably, six isolates harbored multiple PMQR genes. Furthermore, 9.3% and 3.8% of the overall isolates were resistant to nalidixic acid (NAL) and ciprofloxacin (CIP), respectively. PMQR-positive isolates showed higher rates of non-susceptibility to both NAL (48.2%, n = 68/141) and CIP (92.2%, n = 130/141) compared to PMQR-negative isolates (NAL: 8.9%, n = 23/258; CIP: 11.2%, n = 30/258). CONCLUSIONS: The high prevalence of Salmonella spp., significant PMQR-positive, and reduced susceptibility isolates in canal water is of public health concern in Bangkok.

Genomic analysis of Salmonella isolated from canal water in Bangkok, Thailand.

Antimicrobial resistance (AMR) poses an escalating global public health threat. Canals are essential in Thailand, including the capital city, Bangkok, as agricultural and daily water sources. However, the characteristic and antimicrobial-resistance properties of the bacteria in the urban canals have never been elucidated. This study employed whole genome sequencing to characterize 30 genomes of a causal pathogenic bacteria, Salmonella enterica, isolated from Bangkok canal water between 2016 and 2020. The dominant serotype was Salmonella Agona. In total, 35 AMR genes and 30 chromosomal-mediated gene mutations were identified, in which 21 strains carried both acquired genes and mutations associated with fluoroquinolone resistance. Virulence factors associated with invasion, adhesion, and survival during infection were detected in all study strains. 75.9% of the study stains were multidrug-resistant and all the strains harbored the necessary virulence factors associated with salmonellosis. One strain carried 20 resistance genes, including mcr-3.1, mutations in GyrA, ParC, and ParE, and typhoid toxin-associated genes. Fifteen plasmid replicon types were detected, with Col(pHAD28) being the most common type. Comparative analysis of nine S. Agona from Bangkok and 167 from public databases revealed that specific clonal lineages of S. Agona might have been circulating between canal water and food sources in Thailand and globally. These findings provide insight into potential pathogens in the aquatic ecosystem and support the inclusion of environmental samples into comprehensive AMR surveillance initiatives as part of a One Health approach. This approach aids in comprehending the rise and dissemination of AMR and devising sustainable intervention strategies.IMPORTANCEBangkok is the capital city of Thailand and home to a large canal network that serves the city in various ways. The presence of pathogenic and antimicrobial-resistant Salmonella is alarming and poses a significant public health risk. The present study is the first characterization of the genomic of Salmonella strains from Bangkok canal water. Twenty-two of 29 strains (75.9%) were multidrug-resistant Salmonella and all the strains carried essential virulence factors for pathogenesis. Various plasmid types were identified in these strains, potentially facilitating the horizontal transfer of AMR genes. Additional investigations indicated a potential circulation of S. Agona between canal water and food sources in Thailand. The current study underscores the role of environmental water in an urban city as a reservoir of pathogens and these data obtained can serve as a basis for public health risk assessment and help shape intervention strategies to combat AMR challenges in Thailand.

Multilocus Sequence Typing and Virulence Potential of Vibrio parahaemolyticus Strains Isolated from Aquatic Bird Feces.

Vibrio parahaemolyticus is a Gram-negative, foodborne pathogenic bacterium that causes human gastroenteritis. This organism is ubiquitously present in the marine environment. Detection of V. parahaemolyticus in aquatic birds has been previously reported; however, the characterization of isolates of this bacterium recovered from these birds remains limited. The present study isolated and characterized V. parahaemolyticus from aquatic bird feces at the Bangpu Recreation Center (Samut Prakan province, Thailand) from 2016 to 2017, using multilocus sequence typing (MLST) and genome analysis. The results showed that V. parahaemolyticus was present in 34.9% (76/218) of the collected bird fecal samples. Among the ldh-positive V. parahaemolyticus isolates (n = 308), 1% (3/308) were positive for tdh, 1.3% (4/308) were positive for trh, and 0.3% (1/308) were positive for both tdh and trh. In turn, the MLST analysis revealed that 49 selected V. parahaemolyticus isolates resolved to 36 STs, 26 of which were novel (72.2%). Moreover, a total of 10 identified STs were identical to globally reported pathogenic strains (ST1309, ST1919, ST491, ST799, and ST2516) and environmental strains (ST1879, ST985, ST288, ST1925, and ST260). The genome analysis of isolates possessing tdh and/or trh (ST985, ST1923, ST1924, ST1929 and ST2516) demonstrated that the organization of the T3SS2α and T3SS2ß genes in bird fecal isolates were almost identical to those of human clinical strains posing public health concerns of pathogen dissemination in the recreational area. The results of this study suggest that aquatic birds are natural reservoirs of new strains with high genetic diversity and are alternative sources of potentially pathogenic V. parahaemolyticus in the marine environment. IMPORTANCE To our knowledge, infection of foodborne bacterium V. parahamolyticus occurs via the consumption of undercooked seafood contaminated with pathogenic strains. Aquatic bird is a neglectable source that can transmit V. parahaemolyticus along coastal areas. This study reported the detection of potentially pathogenic V. parahamolyticus harboring virulence genes from aquatic bird feces at the recreational center situated near the Gulf of Thailand. These strains shared identical genetic profile to the clinical isolates that previously reported in many countries. Furthermore, the strains from aquatic birds showed extremely high genetic diversity. Our research pointed out that the aquatic bird is possibly involved in the evolution of novel strains of V. parahaemolyticus and play a role in dissimilation of the potentially pathogenic strains across geographical distance.

Characterization of Vibrio parahaemolyticus strains isolated from clinically asymptomatic seafood workers.

Vibrio parahaemolyticus (VP) is a major cause of gastroenteritis outbreaks in Thailand and other countries due to the consumption of contaminated and undercooked seafood. However, there have been few reports of the molecular epidemiology of VP isolates from asymptomatic seafood handlers. Here, we report the phenotypic and genetic characterization of 61 VP isolates obtained from asymptomatic workers in two seafood-processing plants. We found 24 O:K serotypes, of which O11:KUT, O1:KUT and O3:KUT were the dominant serotypes. Analysis by PCR showed that 12 isolates harbored either tdh or trh genes with the potential to be pathogenic VP strains. The presence of T3SS2α and T3SS2ß genes was correlated with the presence of tdh and trh, respectively. Four tdh+ isolates were positive for pandemic marker. In this study, VP isolates were commonly resistant to ampicillin, cephazolin, fosfomycin and novobiocin. Phylogenetic analysis of VP1680 loci in 35 isolates from 17 asymptomatic workers, 6 gastroenteritis patients, 7 environmental samples and 5 genomes from a database showed 22 different alleles. Gene VP1680 was conserved in tdh+ isolates and pandemic strains, while that of trh + isolates was diverse. Asymptomatic workers carrying VP were the most likely source of contamination, which raises concerns over food safety in seafood-processing plants.