Leptospirosis is an important zoonotic disease that is often associated with animal carriers and contamination of the environment via infected urine. This study aimed to assess pathogenic leptospiral carriage in Nan province, a rural area of Thailand where leptospirosis is endemic. Samples from 20 villages were obtained during the period 2013 to 2016, comprising urine samples collected from asymptomatic people (n=37) and domestic animals (n=342), and environmental water samples (n=14). Leptospira were cultured in Ellinghauson McCullough Johnson and Harris (EMJH) media. An rrs nested PCR identified 9.92% (95% confidence interval (CI) 6.96-12.88) of the urine and water samples as being positive for Leptospira spp., and phylogenetic analysis was conducted on the 443bp amplicons. Leptospira weilii, which has not previously been identified in Thailand, was recovered from 13 cattle, 9 pigs, 2 dogs, 2 water samples and 1 goat. L. interrogans was found in 4 dogs, 3 pigs, 3 cattle, 1 human and 1 water sample. Four leptospiral strains were isolated and multilocus sequence typing (MLST) analysis was performed on these. Three novel sequence types were identified, including two singletons of L. interrogans in ST26 and ST33, and one of L. weilii in ST94, with this having a close relationship to previous isolates from cases of human leptospirosis in Laos and China. Our results revealed that pathogenic Leptospira occur commonly in asymptomatic domestic animals, humans and environmental water samples in Nan Province, and emphasize the high potential for zoonotic transmission in the province.

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This study examined antimicrobial resistance (AMR) profiles in commensal Escherichia coli derived from healthy fattening pigs in Thai farms that used prophylactic antimicrobials (in-feed tiamulin fumarate and amoxicillin) [PAs], therapeutic antimicrobials (injectable enrofloxacin or gentamicin) [TAs], or no antimicrobials [NAs]. Commensal E. coli were used as a proxy for overall AMR on the farms. There was a high level of multidrug resistance in all three categories of farm, with isolates showing resistance to β-lactams (amoxicillin, ampicillin, and piperacillin) and tetracyclines (tetracycline), and commonly possessing tetA, bla, and plasmid replicons FIB and F. On the other hand, isolates with an extended-spectrum beta-lactamase phenotype (ESBLP) and with resistance to aminoglycosides, chloramphenicol, fluoroquinolones, nitrofurantoin, tiamulin, and trimethoprim/sulfamethoxazole were significantly more common among the PA farms (p < 0.05) than in the other two farm categories. In the PA farms, ESBLP E. coli commonly contained the bla group, bla group, or both gene groups, and were shown to transfer bla genes in a conjugation experiment. E. coli containing N, FIC and A/C replicons were found only in PA farms. In summary, although E. coli isolates from all farms contained a core set of resistance to β-lactams and tetracyclines, the routine use of PA increased resistance rates to other important antimicrobials.