Prevalence of Salmonella and Escherichia coli O157 from Acute Diarrheic Children in the Mekong Delta, Vietnam

Antibiotic and colistin resistance pattern of Salmonella spp. isolated from pediatric patients with diarrhea in the Southern region of Vietnam

Background

Salmonella spp. is a prominent causative agent of pediatric diarrhea, with recent research emphasizing the rising concern regarding antimicrobial resistance (AMR), particularly involving colistin, a last-resort antibiotic.

Methods

This study involved the collection of 500 stool samples from children with diarrhea from two tertiary pediatric hospitals in Ho Chi Minh City. Conventional methods were used to isolate Salmonella spp., and antibiotic resistance profiling against seven antibiotics was conducted using the disk diffusion method. Colistin resistance was determined by the microdilution method. Colistin resistance (mcr) genes were detected by PCR assay. A conjugation experiment with a multidrug-resistant Salmonella strain and E. coli J53 was performed, and the plasmids from this Salmonella strain were analyzed using bioinformatics.

Results

The Salmonella spp. infection rate was found to be 74/500 (14.8 %). The predominant antibiotic resistance phenotype was ampicillin with 53/74 (71.6 %), followed by trimethoprim-sulfamethoxazole with 23/74 (31.1 %). Resistance rates to ceftazidime, cefotaxime and gentamicin were 14/74 (18.9 %), 13/74 (17.6 %) and 6/74 (8.1 %), respectively. Resistance to imipenem was not observed. Colistin resistance was exhibited in 3/74 (4.1 %) of isolates, all harboring the mcr-1 gene. The plasmid carrying the mcr-1 gene could transfer to E. coli, which belongs to the IncX4 type and contains IS26.

Conclusion

This study provides valuable insights into the antibiotic resistance profiles of Salmonella spp. isolated from pediatric patients, with particular emphasis on colistin resistance.

A review and meta-analysis of non-typhoidal Salmonella in Vietnam: Challenges to the control and antimicrobial resistance traits of a neglected zoonotic pathogen

Non-typhoidal Salmonella (NTS) is a food-borne zoonotic pathogen with important implications for human health. Despite its importance, the burden of NTS infections in Vietnam is unknown. We conducted a systematic review and a meta-analysis to describe the prevalence and phenotypic antimicrobial resistance (AMR) for NTS over time in Vietnam. Following PRISMA guidelines, we identified 72 studies from PubMed and Google Scholar containing data relevant to 'Salmonella', 'Salmonellosis', and 'Vietnam', or 'Viet Nam'. Of those, forty-two papers reporting prevalence of NTS, and twenty-six including data on phenotypic resistance were selected for meta-analysis. The prevalence of NTS ranged from 2% to 5% in humans and from 30% to 41% in samples from animals and the farm/slaughterhouse environment. Between 2000 and 2020 we observed a 27.3% (p = 0.044) increase in absolute terms in prevalence among individuals with enteric diseases and a 12.0% (p = 0.047) increase in aquaculture/seafood samples. The most commonly serovars identified across studies included S. Weltevreden (12.0%), followed by S. Typhimurium (10.1%), S. Derby (6.4%), S. London (5.8%), S. Anatum (4.4%), S. Rissen (3.9%), S. Enteritidis (3.7%), S. Albany (3.3%) and S. 4,[5],12:i:- (3.0%). Over the same period, there was an increasing trend in the pooled AMR prevalence for quinolones (15.6% relative increase), 3rd-, 4th-, and 5th-generation cephalosporins (23.7%), penicillins (16.1%), tetracyclines (12.9%), sulfonamides (8.8%), amphenicol (17.8%), and multidrug resistance (11.4%) (all p ≤ 0.014). A broad range of AMR genes (ARGs) were detected in both human and animal populations. The observed prevalence and AMR trends in Vietnam underscore the need of adopting a One Health strategy encompassing surveillance systems, research initiatives, and awareness campaigns to effectively address the challenges posed by NTS.

A systematic review and meta-analysis of integrated studies on antimicrobial resistance in Vietnam, with a focus on Enterobacteriaceae, from a One Health perspective

Vietnam is a low- and middle-income country (LMIC), a primary food producer, and an antimicrobial resistance (AMR) hotspot. AMR is recognized as a One Health challenge since it may transfer between humans, animals and the environment. This study aimed to apply systematic review and meta-analysis to investigate the phenotypic profiles and correlations of antimicrobial-resistant Enterobacteriaceae across three compartments: humans, animals and the environment in Vietnam. A total of 89 articles found in PubMed, Science Direct, and Google Scholar databases were retrieved for qualitative synthesis. E. coli and non-typhoidal Salmonella (NTS) were the most common bacterial species in studies of all compartments (60/89 studies). Among antimicrobials classified as critically important, the resistance levels were observed to be highest to quinolones, 3rd generation of cephalosporins, penicillins, and aminoglycosides. Of 89 studies, 55 articles reported the resistance prevalence of E. coli and NTS in healthy humans, animals and the environment against ciprofloxacin, ceftazidime, ampicillin, gentamicin, sulfamethoxazole-trimethoprim, chloramphenicol was used for meta-analysis. The pooled prevalence was found highest in E. coli against ampicillin 84.0% (95% CI 73.0-91.0%) and sulfamethoxazole-trimethoprim 66.0% (95% CI 56.0-75.0%) while in NTS they were 34.0% (95% CI 24.0-46.0%), 33.0% (95% CI 25.0-42.0%), respectively. There were no significant differences in the pooled prevalence of E. coli and NTS to these antimicrobials across healthy humans, animals and the environment, except for ceftazidime-resistant E. coli (χ² = 8.29, p = 0.02), chloramphenicol-resistant E.coli (χ² = 9.65, p < 0.01) and chloramphenicol-resistant NTS (χ² = 7.51, p = 0.02). Findings from the multiple meta-regression models indicated that the AMR levels in E. coli (β = 1.887, p < 0.001) and the North (β = 0.798, p = 0.047) had a higher fraction of AMR than NTS and other regions of Vietnam. The outcomes of this study play an important role as the baseline information for further investigation and follow-up intervention strategies to tackle AMR in Vietnam, and more generally, can be adapted to other LMICs.

Wild geckos considered as the natural reservoir of Salmonella Weltevreden in Southeast Asian countries

A total of 1,318 wild geckos were collected in Cambodia, Thailand and Vietnam (Hue and the Mekong Delta) from 2012 to 2015 to determine the prevalence of Salmonella Weltevreden. Those geckos belong to three species: common house gecko (Hemidactylus frenatus), flat-tailed house gecko (Hemidactylus platyurus) and four-clawed gecko (Gehyra mutilata). Of 1,318 gecko samples, 293 (22.2%) samples were positive for Salmonella in this study. The prevalence of Salmonella in geckos was 46.0% in Thailand, 17.3% in Cambodia and 16.3% in Vietnam. Among the Salmonella isolates, S. Weltevreden was the most predominant serovar (32.1%) isolated from wild geckos in these countries. There was no significant difference in the prevalence of Salmonella among gecko species. All S. Weltevreden isolates (100%) were susceptible to the nine antibiotics examined in this study. The PFGE assay by XbaI enzyme identified 19 different patterns from 75 S. Weltevreden isolates. These isolates showed high genetic heterogenicity, and there were specific types prevalent in each region. Furthermore, S. Weltevreden has been prevalent since the ancient times in this region. The results indicate that wild gecko seems to be an important natural reservoir for S. Weltevreden as well as a source of Salmonella infections in humans in Southeast Asian countries.

Retail fresh vegetables as a potential source of Salmonella infection in the Mekong Delta, Vietnam

From July 2017 to Jan 2019, a total of 572 retail fresh vegetables were collected to clarify the contamination of Salmonella in the Mekong Delta, Vietnam. Salmonella was isolated from 74 (12.9%) of 572 samples. The isolation rate of Salmonella from retail fresh vegetables in the rainy season (15.3%) was significantly higher than that in the dry season (7.6%) (P < 0.05). Of 74 Salmonella isolates, Salmonella Weltevreden was the most predominant serovar (35.1%) identified from retail fresh vegetables in all of the wet markets. All S. Weltevreden isolates (100%) were susceptible to nine antibiotics examined. Thus, retail fresh vegetables were considered as an important potential vehicle of Salmonella transmission to humans in the Mekong Delta. These results provide important data for preventing and controlling human salmonellosis in this area.

The importance of wild gecko as a source of human Salmonella infection

A total of 201 wild geckos from the region of Mekong Delta, Vietnam were collected to determine the viable number and survival period of Salmonella in their feces. Of the 101 samples examined, 24 (23.8%) were Salmonella positive. These 24 geckos excreted Salmonella in their feces in a range of 1 to 8.6 log CFU/g with a mean of 4.5 ± 3.2 log CFU/g. Among the Salmonella serovars, Salmonella Weltevreden was the most predominant serovar (37.5%). Moreover, Salmonella could survive for 6 weeks in gecko feces at room temperature in Vietnam. These results indicate that the wild gecko seems to play an important role as a reservoir for Salmonella and a source of Salmonella infection in humans in Southeast Asian countries.