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Investigation of Putative Selective Pressure Conferring Fitness Advantages in Fluroquinolone Resistant Campylobacter Jejuni

Singer, Randall
University of Minnesota
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We hypothesize that the cumulative set of selection pressures that exists in the chicken and its environment support a measureable and stable ratio between the fluoroquinolone-resistant (FQR) and fluoroquinolone-susceptible (FQS) Campylobacterjejuni subpopulations in the broiler chicken environment. This hypothesis is based on the following observations: i) FQR and FQS C. jejuni can be isolated from the same poultry environment samples, ii) the inter-farm prevalence of FQR C. jejuni in poultry samples has stabilized at approximately 20%, and iii) the increased fitness conferred by FQ resistance in C. jejuni does not appear to result in the elimination of the FQS strains.To address our hypotheses, we will complete the following Specific Aims: Specific Aim 1: Demonstrate that the gyrA point mutation confers fitness benefits to FQR C. jejuni by enhancing iron acquisition and regulation in vitro. Specific Aim 2: Quantify the fitness benefit or cost conferred to FQR C. jejuni in the presence or absence of the anti-DNA gyrase bacteriocin, MccB17.Specific Aim 3: Examine the subpopulation dynamic between FQR and FQS C. jejuni in the natural broiler chicken environment.
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Campylobacteriosis, primarily caused by Campylobacter jejuni, is a serious foodborne disease in humans globally, and chicken is considered to be the primary source of infection. Although not always necessary, antibiotic treatment of campylobacteriosis in humans is often warranted, and the critically important fluoroquinolone (FQ) antibiotic class is one of the frontline treatments for Campylobacter infections. Treatment of Campylobacter infections with FQ can be complicated by resistance. The FQ antibiotics were eliminated from use in U.S. poultry in 2005, but since that time, the prevalence of FQ-resistant (FQR) C. jejuni in poultry, poultry products and human infections has continued to rise in the absence of this direct selection pressure in poultry. Incredibly, factors enabling the FQR Campylobacter subpopulation to thrive in the broiler chicken environment remain elusive. This study will investigate different mechanisms that could be helping maintain the FQ resistance observed in Campylobacter of chickens, even in the absence of FQ use. Findings from this project will significantly improve our understanding of the ecology of FQR C. jejuni within-host and aid in developing effective mitigation programs specifically targeting FQR C. jejuni in broiler chickens.
Funding Source
Nat'l. Inst. of Food and Agriculture
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Bacterial Pathogens
Natural Toxins
Meat, Poultry, Game