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Transfer of Antimicrobial Resistance from Bacterial Contaminants to Campylobacter spp.


The goal of this project is to determine the role of the bacterial community in the transfer of antimicrobial resistance genes to Campylobacter spp. <P>The specific objectives are to: <OL> <LI> identify the members of the bacterial community from retail broiler meat contaminated with Campylobacter spp. <LI> isolate, identify and determine the level of antimicrobial resistance of Campylobacter spp and the bacterial community isolated from the same samples. </ol>The products from these efforts will generate fundamental knowledge on what are the main bacterial communities in Campylobacter-positive broiler meat and the similarities (or differences) between the antimicrobial profiling of Campylobacter spp. and the associated bacterial community. This project will also enhance the collaboration between food microbiologists and environmental microbiologists to understand antimicrobial resistance by food-borne pathogens. Graduate students will train in an interdisciplinary setting and will learn molecular techniques aimed at elucidating some of the mechanisms of antimicrobial resistance among bacteria. The results will be disseminated in scientific presentations and through referee-journal publications.

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NON-TECHNICAL SUMMARY: The spread of antimicrobial resistance can be partially traced through the spread of resistance genes by the mobile elements carrying them and the bacterial hosts harboring these elements. Antimicrobial-producing microbes are the main donors of resistance genes to susceptible microorganisms. This theory is supported by the strong evidence that some of the most important resistance genes in Gram-positive and Gram-negative bacteria have remarkable similarities. It is well-known that most of the antimicrobial producing bacteria have a soil origin. This is also the case with most of the Campylobacter-associated bacteria in broiler meat. The variation in the diversity of the bacterial community associated with retail broiler products has been reduced over the years. However, this bacterial community, which usually appears as contaminants in plate media used for isolation of Campylobacter spp., is comprised of Acinetobacter baumannii, A. lwoffi, Pseudomonas spp. and Staphylococcus hominis. Some of these bacteria, especially, Acinetobacter are found in diverse environments and include multi-drug resistant strains that are important for human health. In vitro antimicrobial susceptibility testing (AST) of Campylobacter isolates from foods is important because it predicts the level of antimicrobial resistance of the isolate that may infect humans. AST is performed on infectious organisms that warrant antimicrobial chemotherapy if their susceptibility cannot be predicted in a reliable fashion. Because resistance patterns for Campylobacter have changed significantly over the years, there is a lack of predictability and the surveillance of antimicrobial susceptibility becomes imperative.

<P>APPROACH: The identification of Campylobacter-associated bacteria from broiler retails samples will be done by rinsing the meat products with buffered peptone water, concentrating the bacterial cells and extracting DNA for denaturing gradient gel electrophoresis (DGGE) analysis. DGGE is commonly used in studies of microbial communities to provide information on the diversity of the bacteria present, with the ability to extract and sequence specific bands from the polyacrylamide gel. The samples will also be tested for the presence of Campylobacter (enrichment and plating). Campylobacter isolates will be speciated with multiplex polymerase chain reaction (PCR) assays. PCR-restriction fragment length polymorphism or pulsed-field gel electrophoresis (PFGE) will be used to obtain a fingerprinting profile for each of the Campylobacter and bacterial community strain. Strains will also be tested for their antimicrobial resistance profiles using E-test and broth microdilution methods according to the Clinical and Laboratory Standards Institute.

Oyarzabal, Omar
Auburn University
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