Colistin resistance and plasmid-mediated mcr genes in Escherichia coli and Salmonella isolated from pigs, pig carcass and pork in Thailand, Lao PDR and Cambodia border provinces.

BACKGROUND: Colistin and carbapenem-resistant bacteria have emerged and become a serious public health concern, but their epidemiological data is still limited. OBJECTIVES: This study examined colistin and carbapenem resistance in Escherichia coli and Salmonella from pigs, pig carcasses, and pork in Thailand, Lao PDR, and Cambodia border provinces. METHODS: The phenotypic and genotypic resistance to colistin and meropenem was determined in E. coli and Salmonella obtained from pigs, pig carcasses, and pork (n = 1,619). A conjugative experiment was performed in all isolates carrying the mcr gene (s) (n = 68). The plasmid replicon type was determined in the isolates carrying a conjugative plasmid with mcr by PCR-based replicon typing (n = 7). The genetic relatedness of mcr-positive Salmonella (n = 11) was investigated by multi-locus sequence typing. RESULTS: Colistin resistance was more common in E. coli (8%) than Salmonella (1%). The highest resistance rate was found in E. coli (17.8%) and Salmonella (1.7%) from Cambodia. Colistin-resistance genes, mcr-1, mcr-3, and mcr-5, were identified, of which mcr-1 and mcr-3 were predominant in E. coli (5.8%) and Salmonella (1.7%), respectively. The mcr-5 gene was observed in E. coli from pork in Cambodia. Two colistin-susceptible pig isolates from Thailand carried both mcr-1 and mcr-3. Seven E. coli and Salmonella isolates contained mcr-1 or mcr-3 associated with the IncF and IncI plasmids. The mcr-positive Salmonella from Thailand and Cambodia were categorized into two clusters with 94%-97% similarity. None of these clusters was meropenem resistant. CONCLUSIONS: Colistin-resistant E. coli and Salmonella were distributed in pigs, pig carcasses, and pork in the border areas. Undivided-One Health collaboration is needed to address the issue.

Antimicrobial Resistance Phenotypes and Genotypes of Salmonella spp. Isolated from Commercial Duck Meat Production in Thailand and Their Minimal Inhibitory Concentration of Disinfectants.

Salmonella is an important foodborne bacterium that has become increasingly resistant to critical antimicrobial and disinfectant agents. The aim of this study was to characterize antimicrobial and disinfectant resistance of Salmonella spp. isolated from ducks raised for meat in Nakhon Pathom province, Thailand. A total of 694 fecal samples from ducks were collected in 2018. Of which, 85 samples were positive for Salmonella (12.2%), and 12 Salmonella serovars were identified from 125 Salmonella isolates. The Altona serovar was the predominant serotype found in this study (36.5%). All isolates showed resistance to at least one class of antimicrobial, and 23.2% displayed multidrug resistance (MDR) phenotype. The blaTEM, aadA2, strA, and dfrA12 genes were detected in antibiotic-resistant strains of Salmonella, whereas the genes within a plasmid-borne qnr family that presented in fluoroquinolone-susceptible Salmonella strains were qnrB (3.8%) and qnrS (1.5%). The minimum inhibitory concentrations of benzalkonium chloride (BKC), cetylpyridium chloride (CPC), and hexadecyltrimethyl ammonium bromide (CTAB) ranged between 128 and 512 µg/mL, while that of didecyldimethylammonium chloride (DDAC) was between 32 and 128 µg/mL. The presences of qacEΔ1, mdfA, sugE(c), sugE(p), and ydgE genes were less prevalent (0.8-1.6%). Taken together, our results indicate that duck is an important source of Salmonella with antimicrobial resistance in food-producing animals. Active surveillance programs for antimicrobial and disinfectant resistance in duck production are needed for an early detection of resistance strains of public health importance.

Presence and Transfer of Antimicrobial Resistance Determinants in Escherichia coli in Pigs, Pork, and Humans in Thailand and Lao PDR Border Provinces.

This study aimed to investigate antimicrobial resistance (AMR) characteristics of Escherichia coli isolates from pig origin (including pigs, pig carcass, and pork) and humans in Thailand and Lao People's Democratic Republic (PDR) border provinces. The majority of the E. coli isolates from Thailand (69.7%) and Lao PDR (63.3%) exhibited multidrug resistance. Class 1 integrons with resistance gene cassettes were common (n = 43), of which the most predominant resistance gene cassette was aadA1. The percentage of extended-spectrum beta-lactamase (ESBL) producers was 3.4 in Thailand and 3.2 in Lao PDR. The ESBL genes found were blaCTX-M14, blaCTX-M27, and blaCTX-M55, of which blaCTX-M55 was the most common (58.6%). Ser-83-Leu and Asp-87-Asn were the predominant amino acid changes in GyrA of ciprofloxacin-resistant isolates. Twenty-two percent of all isolates were positive for qnrS. Class 1 integrons carrying aadA1 from pigs (n = 1) and ESBL genes (blaCTX-M55 and blaCTX-M14) from pigs (n = 2), pork (n = 1), and humans (n = 7) were located on conjugative plasmids. Most plasmids (29.3%) were typed in the IncFrepB group. In conclusion, AMR E. coli are common in pig origin and humans in these areas. The findings confirm AMR as One Health issue, and highlight the need for comprehensive and unified collaborations within and between sectors on research and policy.

Prevalence, antimicrobial resistance, virulence gene, and class 1 integrons of Enterococcus faecium and Enterococcus faecalis from pigs, pork and humans in Thai-Laos border provinces.

OBJECTIVES: This study aimed to determine prevalence, antimicrobial resistance, virulence genes, and Class 1 integrons of Enterococcus faecium (E. faecium) and Enterococcus faecalis (E. faecalis) from pigs, pork and humans in Thailand-Laos border provinces. METHODS: Six hundred and forty-eight rectal and carcass swab samples from border provinces of Thailand (n=359) and Lao PDR (n=289) were collected and examined from September 2013 to October 2014. RESULTS: The overall prevalence of Enterococcus species was 483 of 648 (75%), comprising E. faecium (359 of 483, 74.3%) and E. faecalis (124 of 483, 25.7%). The occurrence of E. faecium in pigs, pig carcasses, retail pork, and humans in Thailand was 80.6%, 73.8%, 77.6%, and 67%, respectively. The prevalence of E. faecium was higher in Laos (65.7%) than Thailand (47.1%) (P<0.001). Conversely, E. faecalis was more common in Thailand (24.2%) than Laos (12.8%) (P<0.001). The E. faecium and E. faecalis isolates were resistant to all antimicrobials except vancomycin. High resistance was first observed to tetracycline, erythromycin and streptomycin, followed by gentamicin, ampicillin and chloramphenicol. Both E. faecium (7%) and E. faecalis (0.8%) carried empty Class 1 integrons: E. faecium carried gel (6.4%) and esp (0.8%), while E. faecalis carried agg (41.9%), cylA (36.3%), gel (60.5%), and esp (42.7%). CONCLUSIONS: This study revealed a variable distribution of antimicrobial resistance and virulence genes among E. faecium and E. faecalis from pigs, pig products and humans in Thai-Laos border provinces. These pathogens may serve as potential reservoirs for the maintenance and widespread dissemination of antimicrobial resistance and virulence determinants from animals to humans via the food chain.

Phylogenetic characterization of Salmonella enterica from pig production and humans in Thailand and Laos border provinces.

BACKGROUND AND AIM: The genetic relationship among serotypes of Salmonella enterica from food animals, food of animal origin, and human is of interest as the data could provide an important clue for the source of human infection. This study aimed to determine the genetic relatedness of S. enterica from pig production and human in Thailand-Laos border provinces. MATERIALS AND METHODS: A total of 195 S. enterica serotypes isolated from pig and pork (n=178) and human (n=17) including four serotypes (Typhimurium, Rissen, Derby, and Stanley) were randomly selected to examine their genetic relatedness using highly conserved sequence of three genes (fim A, man B, and mdh). RESULTS: The results showed that 195 Salmonella isolates of four different serotypes were grouped into five different clusters, and members of the same Salmonella serotypes were found in the same cluster. Salmonella isolated from pig production and human in Thailand-Laos border provinces represented overlapping population and revealed a high degree of similarity, indicating close genetic relationship among the isolates. CONCLUSION: The results support that the determination of Salmonella serotyping combined with analysis of phylogenetic tree can be used track the clonal evolution and genetic diversity of Salmonella serotypes in different host species.

High prevalence and molecular characteristics of multidrug-resistant Salmonella in pigs, pork and humans in Thailand and Laos provinces.

This study aimed to examine occurrence and antimicrobial resistance characteristics of Salmonella from pigs, pork and humans in Thailand and Laos provinces. The samples were collected from pigs, carcasses and workers in slaughterhouses, retail pork and butchers in fresh markets and patients in hospitals in Thailand (n=729) and Laos (n=458). A total of 295 of 729 samples (34.6 %) collected in Thailand and 253 of 458 (47.4 %) samples collected in Laos were positive for Salmonella. A total of 548 Salmonella isolates from Thailand (n=295) and Laos (n=253) were further analysed. Serovar Typhimurium was the most common serotype in Thai (34 %) and Laos (20.6 %) samples. Approximately 2.4 % of Thai isolates produced extended-spectrum ß-lactamase (ESBL). All the ESBL producers possessed blaCTX-M-14, some of which were horizontally transferred. Class 1 integrons were common in Thai (31.9 %) and Laos (39.1 %) isolates, but none were associated with SGI1. The resistance cassette dfrA12-aadA2 was the most common, while the least common was aadA2-linG (n=1). The dfrA12-aadA2 gene cassette in five isolates and aadA2-linG were located on conjugative plasmid. Three pork isolates were fluoroquinolone resistant and carried an amino acid substitute, Ser-83-Tyr, in GyrA. The qnrS gene was found in 7.1 and 5.5 % of the Thai and Laos isolates, respectively, while qnrB was carried in another Laos isolate (1.9 %). All ESBL producers carried qnrS. In conclusion, multidrug-resistant Salmonella was common in pigs, pork and human samples in this region. The bacteria carried mobile genetic elements and resistance genes on conjugative plasmids that could be readily transferred to other bacterial species.

Characterization of Antimicrobial Resistance in Salmonella enterica Isolated from Pork, Chicken Meat, and Humans in Northeastern Thailand.

A total of 221 Salmonella enterica from raw pork (n=64), raw chicken (n=80), and humans (n=77) were characterized for antimicrobial resistance phenotypes and genotypes and virulence plasmid-associated genes. Most Salmonella isolates (95.9%) were multidrug resistant and exhibited high resistance to sulfamethoxazole (96.4%), streptomycin (93.2%), spectinomycin (76.5%), tetracycline (73.3%), ampicillin (70.1%), and trimethoprim (60.2%). Forty-one percent of all isolates were intI1-positive, of which 60% carried class 1 integrons with variable region ranging in size from 0.2 to 2.0 kb. Six integron profiles (IP-I to IP-VI) were defined. The dfrA12-aadA2 cassette was most prevalent (66.7%). Class 1 integrons with the dfrA12-aadA2 cassette in five pork isolates could be horizontally transferred. Three pork isolates carried Salmonella genomic island 1 (SGI1), of which a serovar Anatum harbored SGI1 gene cluster located between thdF and int2. Two single-point mutations (i.e., G-259-T and C-248-T) in gyrA leading to Asp-87-Tyr and Ser-83-Phe substitutions in GyrA, respectively, were detected. Of all plasmid-mediated quinolone resistance genes tested, only qnrS (4.1%) and qnrB (1.8%) were found. The virulence plasmid-associated genes including spvC, pefA, and rck were identified in 8.1%, 1.8%, and 1.4% of all Salmonella isolates, respectively.