RESUMEN
BACKGROUND AND AIM: Salmonella enterica is an important foodborne pathogen and is recognized as a major public health issue. The emergence of multidrug-resistant (MDR) S. enterica represents a major challenge for national public health authorities. We investigated the distribution of serovars and antimicrobial resistance of S. enterica isolates from clinical swine samples stored at the Veterinary Diagnostic Laboratory, Faculty of Veterinary Medicine, Kasetsart University from 2016 to 2017. MATERIALS AND METHODS: Clinical samples were collected and subjected to standard microbiological techniques outlined in the Manual of Clinical Microbiology to identify Salmonella serovars. Susceptibility to antimicrobials was tested by the Kirby-Bauer disk diffusion method using a panel of 14 antimicrobials. RESULTS: A total of 144 Salmonella isolates were identified and the dominant serovar was Salmonella Choleraesuis (66.67%), followed by monophasic Salmonella Typhimurium (18.75%), S. Typhimurium (9.03%), and Rissen (5.56%). The isolates displayed high resistance rates to ampicillin (AMP [100%]), amoxicillin (AX [100%]), tetracycline (TE [100%]), cefotaxime (CTX [89.58%]), ceftriaxone (CRO [87.50%]), chloramphenicol (C [82.64%]), gentamicin (CN [79.17%]), nalidixic acid (NA [72.92%]), and ceftazidime (CAZ [71.53%]). All isolates were MDR, with 29 distinct resistance patterns. The dominant MDR pattern among serovars Choleraesuis and Rissen exhibited resistance to 9 antimicrobials: (R7-14 AMP-AX-CAZ-CRO-CTX-NA-C-CN-TE). However, all tested isolates were susceptible to AX/clavulanic acid and fosfomycin. CONCLUSION: High resistance levels to the third generation of cephalosporins such as CAZ, CRO, and CTX highlight the need for careful and reasonable usage of antimicrobials in animals and humans, especially for S. Choleraesuis infections.
RESUMEN
The prevalence of intermediately virulent Rhodococcus equi isolates from pig submaxillary lymph nodes from four slaughterhouses in Nakhonpathom province, Thailand, was investigated. The isolates were tested for the presence of virulence plasmids and the 20-kDa virulence-associated protein antigen (VapB) gene by PCR. Of the 734 submaxillary lymph nodes tested, 19 (2.6%) produced positive cultures of R. equi. All 19 isolates were positive for the VapB gene and contained virulence plasmids that were identified as type 1 (six isolates), type 6 (two isolates), type 7 (one isolate), type 16 (two isolates), and a new variant (eight isolates). Based on the restriction digestion patterns of the plasmid DNAs, we tentatively designated the variant as type 18. Investigation of the prevalence and plasmid profiles of VapB-positive R. equi in pigs should be extended throughout Thailand to evaluate potential sources of zoonotic infections.
