| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 99 === Enterococcus spp., along with gram-positive coccus, are important bacteria found in a number of nature habitats including soil, water, plants, and also part of normal intestinal flora in humans and other animals. They can lead the cause of nosocomial infections, in which the prevalence of enterococcal resistance to antibiotics become major concerns. Now the use of antimicrobial agents has been widespread dependent on food animals. It has resulted in a rise of antimicrobial resistant strains of bacteria. Enterococci and E. coli can transfer antimicrobial resistant genes to another bacterial species. Therefore, the relationships between antibiotic uses and resistance in dairy farms are needed to be accurately investigated. The aims of this study are to understand the prevalence about antimicrobial resistance by disc diffusion tests and to detect tetracycline resistant genes by multiplex PCR in enterococcal strains from dairy farms in Taiwan. A total of 218 enterococcal isolates were collected from raw milk samples, fecal samples, and diarrheic feces. The result of antibiotic resistance tests was shown with a large proportion of strains resistant to cloxacillin (97.2%, 212/218), cefuroxime (94.5%, 206/218), and amikacin (83.9%, 183/218). The most susceptible drugs were amoxycillin-clavulanic acid (97.7%, 213/218), ampicillin (97.2%, 212/218), and penicillin (95.4%, 208/218). All of enterococcal strains collected from this study revealed a variety of resistance profiles to the tested antibiotics and presented multi-resistance to at least 3 antimicrobial agents. The tetracycline resistant genes were detected in 86 strains (39.4%) from 218 enterococcal isolates by multiplex PCR. The PCR products were analyzed with gene sequencing and sequence alignments. We found 4 tetracycline resistant genes in this study, including tet M (22%, 48/218), tet L (17.9%, 39/218), tet O (8.3%, 18/218), and tet S (0.9%, 2/218) genes. While tet M and tet L genes exist at relatively high frequencies (22.0% and 17.9%) in enterococci in our study. There were total 20 strains (23.3%, 20/86) containing 2 tetracycline resistant genes. According to our results of study in multi-drug resistance in enterococci, the use of antibiotics must be carefully and controled in process of therapy and in agriculture industries.
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