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 b-lactamase (ESBL). All the ESBL producers possessed bla CTX-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.
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.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.