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A. Increased human morbidity

Due to their enhanced survivability in the presence of antibiotic concentrations, infectious agents possessing AMR traits gain an enhanced potential for transmission, incidence and persistence. This can result in their dominance over the prevailing microflora within mammalian host populations, leading to higher rates of transmission as compared to the susceptible bacterial strains.  This is particularly important for zoonotic agents present in animal carriers in which the bacteria have gained the ability to resist antibiotics important for their treatment, control and prevention.  Their enhanced ability to survive, thrive, prevail and resist treatment allows these resistant bacteria to be carried and maintained in their host animals, and therefore facilitates their spread to other susceptible hosts, including humans.

Examples are the increasing frequency of quinolone resistance among Salmonella Enteritidis5 and Campylobacter spp isolated from animals and people6,7 and the multiple resistance of Salmonella Typhimurium for ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (ACSSuT)8

Campylobacter Resistance and Fluoroquinolones

p06_01.jpgThe emergence of fluoroquinolone resistance among domestically acquired human infections with Campylobacter jejuni and E. coli is an example of AMR thought to have resulted from the use of antimicrobial agents in food animals with subsequent transmission of resistant bacteria to humans via the food supply7.   Both molecular and epidemiological evidence indicate that the resulting AMR prevalence among humans was triggered by the introduction of enrofloxacin in poultry, prompting FDA to withdraw its approval for use in poultry in 200511


AMR In Foodborne Pathogens

Although resistance in strictly human pathogens such as Shigella spp. and Salmonella typhi is primarily attributed to the use of antibiotic agents in human populations, the use of antibiotics in animal agriculture is thought to be the principal driver of increasing resistance for many enteric zoonotic infectious agents for which animal populations serve as the principal epidemiological reservoir.  The Department of Health and Human Services (HHS), Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) believe that resistant strains of three major bacterial pathogens in humans – Salmonella, Campylobacter and E. coli - are linked to the use of antibiotics in foodborne animals9.  These organisms are three of the top five major foodborne agents that account for an estimated 90% of deaths resulting from infection with foodborne pathogen in the United States10 .  

Increasing frequency of quinolone resistance among human and animal isolates has been shown in Salmonella Enteritidis and Campylobacter spp (see graph). Multiple resistance of Salmonella Typhimurium to ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (ACSSuT)  have also been observed. Most reports relate these increasing trends to the subtherapeutic use of antimicrobials in livestock and poultry.










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