Colistin Resistance and ESBL Production in Salmonella and Escherichia coli from Pigs and Pork in the Thailand, Cambodia, Lao PDR, and Myanmar Border Area

Abstract

The study aimed to examine the prevalence and genetic characteristics of ESBL-production and colistin resistance in Salmonella and Escherichia coli from pigs and pork in the border area among Thailand, Cambodia, Lao PDR, and Myanmar. Salmonella (n = 463) and E. coli (n = 767) isolates were collected from pig rectal swab from slaughterhouses (n = 441) and pork from retail markets (n = 368) during October 2017 and March 2018. All were determined for susceptibility to colistin and cephalosporins, ESBL production and mcr and ESBL genes. Salmonella was predominantly found in Cambodia (65.8%). Serovars Rissen (35.6%) and Anatum (15.3%) were the most common. The E. coli prevalence in pork was above 91% in all countries. Colistin-resistance rate in E. coli (10.4%) was significantly higher than Salmonella (2.6%). ESBL-producing Salmonella (1.9%) and E. coli (6.3%) were detected. The blaCTX-M-55 and blaCTX-M-14 were identified. The mcr-1 gene was detected in Salmonella (n = 12) and E. coli (n = 68). The mcr-1/blaCTX-M-55 and mcr-3/blaCTX-M-55 co-concurrence was observed in one Salmonella and three E. coli isolates, respectively. In conclusion, pigs and pork serve as carriers of colistin and new generation cephalosporins resistance. Testing for resistance to last line antibiotics should be included in national AMR surveillance program using One Health approach.

Virulence Determinants and Plasmid-Mediated Colistin Resistance mcr Genes in Gram-Negative Bacteria Isolated From Bovine Milk

“…The high proportion of colistin-resistant bacteria and the diversity of mcr variants detected here indicates a lot of independent acquisitions of mcr genes by colistin-sensitive bacteria and confirm the hypothesis that animals and food chain may play a key role in mcr transmission ( Luo et al., 2020 ). This is considering an alarming ratio since previous studies have detected colistin resistance in 37%, 40%, and 41% of bacterial isolates from pigs, poultry, and human clinical samples, respectively ( Savin et al., 2020 ; Lay et al., 2021 ; Qadi et al., 2021 ). Of note, we identified these isolates in milk samples, which included various bacterial species.…”

Longitudinal Monitoring Reveals Persistence of Colistin-Resistant Escherichia coli on a Pig Farm Following Cessation of Colistin Use

“…Following the first identification of mcr -1 during nation-wide surveillance in Thailand ( 19 ), from the start of 2017 the Department of Livestock and Development (DLD) has prohibited prophylactic use of colistin sulfate in pig farms. Data regarding colistin resistance in bacteria from livestock in Thailand is still limited, although mcr positive E. coli have been detected in pig slaughterhouses from the Thailand border areas even after implementation of the colistin withdraw policy ( 20 ). Therefore, currently it is still debatable how this withdrawal of colistin usage may have influenced the emergence and spread of mcr genes in pigs and in the farm environment ( 21 ).…”

Genomic Epidemiology of Multidrug-Resistant Nontyphoidal Salmonella in Young Children Hospitalized for Gastroenteritis

“…bla CTX-M-55 was also recently identified specifically in Salmonella spp. from pigs/pork in both Thailand and Lao PDR ( 24 ), while bla CTX-M-55 was identified in Escherichia coli from pig slaughterhouses/retail markets of these countries as well as from Cambodia and Myanmar. Further studies on animal food sources may define the widespread presence of CTX-M-55 in this region.…”