99D-10 |
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L. D. GOODRIDGE, Dept. of Animal Science, Univ. of Wyoming, PO Box 3684, Laramie, WY 82071-3684 The increased use of antimicrobials in human and veterinary medicine, and agriculture, has created enormous pressure for the selection of antimicrobial resistance among bacterial pathogens. Recent foodborne outbreaks of Salmonella enterica serotype Newport infection appears to be related to the recent emergence of multiple antimicrobial resistant strains of S. Newport. These strains are resistant to multiple antimicrobials, including third generation cephalosporins such as ceftriaxone, an antimicrobial agent commonly used to treat serious Salmonella infections in children. The objective of this study was to use the techniques of ribotyping, pulsed field gel electrophoresis, plasmid profiles and integron analysis to investigate the degree of DNA banding polymorphism exhibited by strains of antimicrobial resistant S. Newport. Antimicrobial resistance of the S. Newport isolates was determined using the Sensititre automated antimicrobial susceptibility system. Ribotyping was accomplished using the Dupont Qualicon Riboprinter. Pulsed field gel electrophoresis was performed according to the directions of the Centers for Disease Control and Prevention (CDC). Plasmid and integron analysis were performed according to previously described methods. PFGE and ribotype profiles were used to compare the genetic relatedness of the S. Newport isolates. Both methods clearly resolved the S. Newport isolates into eight distinct clusters. Plasmid analysis revealed that most isolates contained plasmids ranging in size from 2.0 - 23.0 kb. Class 1 integrons were observed in many of the isolates, and several isolates contained more than one integron. Restriction fragment length polymorphism (RFLP) indicated that integrons of the same size were identical. These results demonstrate the high degree of DNA banding pattern polymorphism found in some strains of antimicrobial resistant S. Newport, and illustrates the presence of complex genetic structures contained within the isolates, which may be involved in the rapid spread of antibiotic resistance among S. Newport strains.
Session 99D, Food Microbiology: General
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