| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 98 === Antimicrobial resistance is a growing concern for public and animal health in modern medicine. Threats to public health could come from the transfer of pathogens between animals and people via direct contact or indirect contact such as through food. Escherichia coli is one of the most common pathogens which induce such as mastitis, diarrhea, pneumonia, omphalitis in dairy farms. To accurately characterize the relationship between antibiotic use and resistance in dairy farms, epidemiological definitions are needed. The aim of this study was to detect the resistance determinats by use of disk diffusion method and specific oligonucleotide primers for amplifying three β-lactamases genes: blaTEM, blaSHV, and blaOXA-1. In the result of this study, a total of 137 pathogenic E. coli was obtained from raw milk samples, diarrheic feces, omphalitis, uterine infection cases, and lung tissue samples from 63 dairy farms in Taiwan. The result of antibiotic resistance tests was showed with a large proportion of isolates resistant to ampicillin (35.3%), oxytetracycline (50.0%), and cloxacillin (87.5%). Upon testing for β-lactamases genes, the blaTEM-1 was detected in 76 strains (55.5%) from 137 E. coli isolates. However, none of these isolates contained either blaSHV or blaOXA-1 genes. Dendrograms of phylogenetic relationships with blaTEM-1 gene detected from 76 E. coli were very similar (97%-100%), except one (95%) obtained from a fecal sample. According to our results, approximately 90% of strains of E. coli revealed a variety of resistance profiles to the tested antibiotics. Multiplex antimicrobial resistance (≥ 2 antimicrobial) was observed in 77 (56.2%) of E. coli isolates. The prevalence of the antibiotic resistance patterns and the blaTEM-1 gene in our finding was lower than in other researches but the resistant trend was identically. The results may indicate that the susceptibility profile of the causal bacteria should be determined before empirical therapy is started. blaTEM-1 was the predominant β-Lactamase from gram negative isolates worldwide and the most common resistance gene among pathogenic E. coli isolated from dairy farms in Taiwan. Therefore, a long period of surveillance programs is necessary for better understanding about this bacterium and more effective therapy in diseases infected with E. coli.
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