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.

Recovery and Quantification of Norovirus in Air Samples from Experimentally Produced Aerosols

Norovirus is the leading cause of acute gastroenteritis in humans across all age groups worldwide. Norovirus-infected patients can produce aerosolized droplets which play a role in gastroenteritis transmission. The study aimed to assess bioaerosol sampling in combination with a virus concentrating procedure to facilitate molecular detection of norovirus genogroup (G) II from experimentally contaminated aerosols. Using a nebulizer within an experimental chamber, aerosols of norovirus GII were generated at known concentrations. Air samples were then collected in both 5 mL and 20 mL water using the SKC BioSampler at a flow rate of 12.5 L/min, 15 min. Subsequently, the virus in collected water was concentrated using speedVac centrifugation and quantified by RT-qPCR. The optimal distances between the nebulizer and the SKC BioSampler yielded high recoveries of the virus for both 5 and 20 mL collections. Following nebulization, norovirus GII RNA was detectable up to 120 min in 5 mL and up to 240 min in 20 mL collection. The concentrations of norovirus GII RNA recovered from air samples in the aerosol chamber ranged from 102 to 105 genome copies/mL, with average recoveries of 25 ± 12% for 5 mL and 22 ± 19% for 20 mL collections. These findings provide quantitative data on norovirus GII in aerosols and introduce a novel virus concentrating method for aerosol collection in water, thus enhancing surveillance of this virus.

Genetic diversity and antimicrobial resistance pattern of Salmonella enterica serovar Enteritidis clinical isolates in Thailand

OBJECTIVE

To trace the history of antimicrobial resistance in Salmonella enterica serovar Enteritidis (S. Enteritidis, SE) circulating in Thailand, we characterised clinical isolates obtained during 2004-2007.

METHODS

Antimicrobial resistance profiles, multi-locus variable number tandem repeat analysis (MLVA) types and 3 representative virulence determinants (spvA, sodCI and sopE) were established from SE isolates (n = 192) collected from stool and blood of patients throughout Thailand during the period 2004-2007.

RESULTS

Resistance was found in SE against 10 out of 11 antimicrobials studied. The highest resistance ratios were observed for nalidixic acid (83.2%), ciprofloxacin (51.1%) and ampicillin (50.5%), and 25.5% were multidrug resistant. Based on five polymorphic tandem repeat loci analysis, MLVA identified 20 distinct types with three closely related predominant types. A significant increase of AMP resistance from 2004 to 2006 was strongly correlated with that of a MLVA type, 5-5-11-7-3.

CONCLUSION

The usage of antimicrobials in human medicine or farm settings might act as selective pressures and cause the spread of resistant strains. Hence, a strict policy on antimicrobial usage needs to be implemented to achieve the control of resistant SE in Thailand.