Objectives: The aim of this study was to determine the prevalence of antibiotic-resistant bacteria, especially extended-spectrum beta-lactamase (ESBL) producing Escherichia coli, in samples from healthy adults, foods, food animals, and the environment in selected areas of Thailand. Methods: Samples were collected from stool specimens from adult food factory and food animal farm workers, fresh and cooked foods sold at markets, rectal swabs of healthy pigs and chickens, fresh pork meat from slaughterhouses, water samples from canals as well as fish and shrimp farm ponds, and stagnant water sources on pig farms. Antibiotic susceptibility was determined using the disk diffusion or agar dilution methods. Extended-spectrum beta-lactamase production was assayed using a double disk diffusion method. Results: Among 544 healthy adult food factory workers, 75.5% were positive for ESBL producing E. coli, while 77.3% of E. coli isolated from 30 healthy animal farm workers were positive. Amongst healthy food animals, ESBL producing status among E. coli isolates were more commonly detected in pigs (76.7%) than broilers (40%). Extended-spectrum beta-lactamase producing E. coli seemed to be more prevalent in fresh meat samples than in fresh vegetables, in fresh foods than in cooked foods, and in water samples collected from the animal farms than those from canals and fish and shrimp ponds. Conclusions: Extended-spectrum beta-lactamase producing E. coli isolates are prevalent amongst healthy individuals, foods along the food production chain from farms to consumers, and in the environment in selected areas in Thailand.

Background Infections caused by carbapenemase-producing Enterobacteriaceae (CPE) have continually grown as a global public health threat, with significant mortality rates observed across the world. We examined the clinical data from patients with CPE infections and their outcomes, concentrating on Klebsiella pneumoniae isolates. We analysed the clinical information, performed antimicrobial susceptibility testing, and conducted molecular epidemiological and genomic analyses on the isolates to identify patterns in the data. Methods The clinical characteristics of 33 hospitalised patients with confirmed CPE, including patient-related factors associated with the development of CPE infections, were examined. Patients were divided according to whether they were “colonised” or “infected” with CPE and by the timing and frequency of their rectal swab collections, from which 45 swabs were randomly selected for analysis. CPE isolates were purified, and antimicrobial susceptibility tests performed. Whole genome sequences of these isolates were determined and analysed to compute bacterial multilocus sequence types and plasmid replicon types, infer phylogenetic relationships, and identify antimicrobial resistance and virulence genes. Results Altogether, 88.9% (40/45) of the CPE isolates were K. pneumoniae. The most abundant carbapenemase gene family in the K. pneumoniae isolates (33/39) was blaOXA-232, with blaNDM-1 additionally identified in 19 of them. All CPE isolates carrying either blaOXA-232 or blaNDM-1 were resistant to meropenem, but only 40 from 45 were susceptible to colistin. Among the CPE-infected patients (n = 18) and CPE-colonised patients who developed CPE infections during the study (n = 3), all but one received standard colistin-based combination therapy. Phylogenetic analysis revealed the polyclonal spread of carbapenemase-producing K. pneumoniae (CPKP) within the patient population, with the following two major subclades identified: ST16 (n = 15) and ST231 (n = 14). CPKP-ST231 had the highest virulence score of 4 and was associated with primary bacteraemia. The siderophores yersiniabactin and aerobactin, considered to be important virulence factors, were only identified in the CPKP-ST231 genomes. Conclusions This study has revealed the genomic features of colonising CPE isolates, focusing on antimicrobial resistance and virulence determinants. This type of multi-layered analysis can be further exploited in Thailand and elsewhere to modify the regimes used for empirical antibiotic treatment and improve the management strategies for CPE infections in hospitalised patients.

Long-term use of colistin for preventing Gram-negative bacterial infections in food animals was prohibited in Thailand in 2017, but it is permitted for short-term treatment. This study aimed to investigate association between the use of colistin for short-term treatment of infection and the emergence of colistin-resistant Enterobacteriaceae in swine. The current study was conducted at 2 selected swine farms in Thailand. Neither farm has used colistin to prevent infection for longer than 1 year. Rectal swabs were collected from the same 66 pigs at birth, and on days 7, 14, 21, 28, and 60. Colistin was used to treat sick pigs for up to 3 days. Additional rectal swabs were collected during colistin treatment. Rectal swabs were analyzed for colistin-resistant Enterobacteriaceae and the mcr-1 gene. Results revealed that colistin-resistant Enterobacteriaceae were absent at birth. Some pigs at both farms had diarrhea and received colistin treatment during days 2-27. Colistin-resistant Enterobacteriaceae were detected in 13.3-50.0% of sick and healthy pigs. No sick pigs were observed during days 28-60, and colistin was not used during that period. Colistin-resistant Enterobacteriaceae were detected in 2.8-10.0% of healthy pigs on day 28, and in 0-3.4% of healthy pigs on day 60. The mcr-1 gene was detected in 57.6% of colistin-resistant Enterobacteriaceae isolates. Short-term treatment with colistin was found to be associated with the emergence of colistin-resistant Enterobacteriaceae in swine. Colistin-resistant Enterobacteriaceae rapidly emerged after colistin use, and rapidly decreased or disappeared after its discontinuation.