18D-12 |
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S.-H. KIM1, K.-W. Chang1, Y.-M. Tzou1, C.-I. Wei1, and H. An2. (1) Dept. of Nutritional Sciences, Oklahoma State Univ., 301 HES, Stillwater, OK 74078, (2) School of Pharmacy, Univ. of Southern California, 1985 Zonal Ave., B-4 Pharmaceutical Sciences Ctr., Los Angeles, CA 90089-9121 The emergence of antibiotic-resistant bacteria in livestock and poultry has been attributed to the use of antibiotics to prevent infection and promote growth. The wide use of b-lactam agents in food-animal production has led to rapid evolution of bacterial resistance to the agents by producing hydrolytic enzymes and/or decreasing the active drug concentration via the alteration of permeability in outer membranes. The objective of this study was to characterize the genotype and phenotype resistant profiles of b-lactam-resistant bacteria prevalently detected in poultry and cattle farms and retail meat products. Salmonella spp., Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Acinetobacter spp., and Pseudomonas spp. were primary screened and identified as b-lactam-resistant bacteria. Antibiotic-resistant profiles of these isolates were examined by Kirby-Bauer disc diffusion test. The types of antibiotic-resistant genes and their genetic location in the isolates were determined by polymerase chain reaction assay and DNA sequencing. Conjugal transfer of these resistance genes were evaluated by mating the isolates with antibiotic-susceptible E. coli. Outer membrane profiles of the isolates were analyzed by SDS-PAGE. Among the isolates, Acinetobacter spp. and Pseudomonas spp. were resistant to most of the tested b-lactam agents, such as ampicillin, amoxicillin-clavulanic acid, cefoxitin, ceftiofur, and cephalothin. Their resistance to the agents resulted from alterations of membrane permeability or acquiring b-lactamase genes, blaSHV and blaTEM. Meanwhile, these tested enteric bacteria were mostly resistant to ampicillin by the expression of b-lactamase genes located in plasmids. The blaTEM-1 was detected in Salmonella spp., E. coli, and P. mirabilis, whereas the presence of blaSHV-1 was identified in K. pneumoniae. These genes were also able to transfer to E. coli by transconjugation. This study demonstrated diversity of b-lactam-resistant bacteria in animal farms and retail meat products. In particular, the spread of blaTEM by horizontal transfer was relevant in the tested isolates.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |