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Chapter 13 : Antimicrobial Resistance in Food-Borne Pathogens
Category: Food Microbiology; Applied and Industrial Microbiology
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This chapter focuses on the occurrence of antimicrobial-resistant (AMR) phenotypes among selected food-borne bacteria, with emphasis on isolates recovered from foods of animal origin and the potential public health consequences. Once an AMR determinant becomes widely disseminated in different ecosystems, it is difficult to conduct trace studies to identify particular origins. It may be possible, however, to track the spread of resistant organisms after the introduction of a new animal antimicrobial drug. Continuous monitoring of antimicrobial susceptibility/ resistance profiles in food-borne pathogens is needed in order to identify important trends that signify a need to amend antimicrobial use practices. Bacterial isolates recovered from ill people are sent to the Centers for Disease Control and Prevention (CDC) Coordinating Center for Infectious Diseases in Atlanta, GA, by participating state and local health departments. Enterococci were readily isolated from all retail meats tested, ranging, on average, from 88%of pork chops to 98% of all chicken breasts sampled, which is consistent with other studies from the United States. The enteric habitat of Escherichia coli in animals provides an easy source of contamination for animal-derived meats at slaughter and at points downstream in the food production process. Transmission of resistance genes from normally nonpathogenic species to more virulent organisms within the animal or human intestinal tract may be an important mechanism for acquiring clinically relevant AMR organisms. The evolution and propagation of transmissible plasmids in Salmonella and E. coli carrying resistance to eight or more antimicrobials are particularly worrisome.
Routes of dissemination of AMR bacteria and determinants. Adapted from reference 197a .
Circular representation of the IncA/C backbone (inner circle) and laterally acquired regions (outer circles) on R plasmids from Yersinia ruckeri, Yersinia pestis, and Salmonella serovar Newport. Printed with permission of W. Florian Fricke, University of Maryland School of Medicine, Baltimore.
AMR among E. coli isolates from NARMS retail meats, 2002 to 2005. AMI, amikacin; GEN, gentamicin; KAN, kanamycin; STR, streptomycin; AMP, ampicillin; AMC, amoxicillin-clavulanic acid; TIO, ceftiofur; AXO, ceftriaxone; FOX, cefoxitin; FIS, sulfisoxazole; COT, trimethoprim-sulfamethoxazole; CHL, chloramphenicol; CIP, ciprofloxacin; NAL, nalidixic acid; TET, tetracycline.
AMR among Salmonella isolates from NARMS retail meats, 2002 to 2005. For abbreviations, see legend to Fig. 3 .
Examples of antimicrobials approved for use in animals in the United States a
Number and percentage of retail meats positive for Campylobacter, Salmonella, Enterococcus, and E. coli from NARMS, 2002 to 2006