Streptococcus suis is a leading cause of bacterial meningitis in South-East Asia, with frequent zoonotic transfer to humans associated with close contact with pigs. A small number of invasive lineages are responsible for endemic infection in the swine industry, causing considerable global economic losses. A lack of surveillance and a rising trend in clinical treatment failure has raised concerns of growing antimicrobial resistance (AMR) among invasive S. suis . Gene flow between healthy and disease isolates is poorly understood and, in this study, we sample and sequence a collection of isolates predominantly from healthy pigs in Chiang Mai province, Northern Thailand. Pangenome characterization identified extensive genetic diversity and frequent AMR carriage in isolates from healthy pigs. Multiple AMR genes were identified, conferring resistance to aminoglycosides, lincosamides, tetracycline and macrolides. All isolates were non-susceptible to three or more different antimicrobial classes, and 75 % of non-serotype 2 isolates were non-susceptible to six or more classes (compared to 37.5 % of serotype 2 isolates). AMR genes were found on integrative and conjugative elements previously observed in other species, suggesting a mobile gene pool that can be accessed by invasive disease isolates. This article contains data hosted by Microreact.

Background: MonophasicSalmonellaTyphimurium orS. enterica1,4,[5],12:i:- is among the top five serotypes reported in Thailand. In this study, nineteen monophasicS. Typhimurium from the pig production chain in Chiang Mai and Lamphun provinces during 2011–2014 were sequenced and compared to a globally disseminated clone. Isolates were probed in silico for the presence of antimicrobial resistance genes andSalmonellavirulence factors, including Pathogenicity Islands.Results: All isolates were from sequence type 34 (ST-34) and clustered similarly in core and pangenome genealogies. The two closest related isolates showed differences in only eighteen loci from whole-genome multilocus sequence typing analysis. All 19 isolates carried aminoglycoside and beta-lactam class resistance genes and genes for five or more different antibiotic classes. Seven out of 14 known SPIs were detected, including SPI-5, SPI-13 and SPI-14, which were detected in all isolates.Conclusions: The multi-drug resistant clone, ST-34 was sampled at all stages of pork production. This clone has infiltrated global agricultural processes and poses a significant public health risk. Differences in the core and accessory genomes of the isolates we collected suggest that strains persist though the pork production process, with evidence of mutation within the core-genome and horizontal acquisition of genes, potentially via sharing of pathogenicity islands and plasmids. This highlights the importance of surveillance and targeted intervention measures to successfully controlSalmonellacontamination.

Tadee P, et al. J Vet Sci. 2023 Dec;25(1):e5. https://doi.org/10.4142/jvs.23189

Background: The surrounding areas of the middle Mekong basin, particularly along the border between Thailand and Lao People’s Democratic Republic (Lao PDR), are high-risk areas for many livestock-associated foodborne illnesses, especially salmonellosis. This study aimed to determine the prevalence and characteristics ofSalmonellaspp. contamination in pork, beef and chicken meats sold at retail markets in the Thailand-Laos border area surrounding the Thai-Lao Friendship Bridge I from January to May 2019. We focused on the prevalent serotypes, antimicrobial susceptibility profiles and the multilocus sequence type (MLST) genotypes of the collectedSalmonellastrains.Results: From a total of 370 meat samples collected, 63% were positive forSalmonella, with the prevalence of 73%, 60% and 56% from pork, beef and chicken meat samples, respectively. Of all the positive samples, 53 serotypes were identified. Of these,Salmonella entericaserovar London accounted for the majority (27%), followed by serovars Corvallis (14%), and Rissen (6%). Resistance against tetracycline was found at the highest frequency (50%), followed by ampicillin (35%) and sulfamethoxazole-trimethoprim (28%). MLST revealed no evidence of shared genetic relatedness ofSalmonellaat retail sites among Thailand-Laos border zone. However, a diverse range ofSalmonellagenotypes were spread over the area. Besides, the persistence of the residential pathogen and sharing of the supply route within-country can be inferred.Conclusions: Given the high levels of contamination of retail meats, regular disinfecting of all working areas and quality control checking at pre-retail stage must be applied to reduce the transmission ofSalmonellaand other foodborne pathogens to consumers. The findings of this study will make a significant contribution to the current understanding ofSalmonellaepidemiology to enhance food security in the region.