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Factors Affecting the Emergence of Quinolone-Resistant Campylobacter in Poultry


Since the use of quinolones, one of the most valuable antimicrobials available to treat human infections, in poultry production systems, quinolone-resistant Campylobacter strains have rapidly increased throughout the world and are emerging as a major threat to public health.
The objectives of this project are to:
<li> Determine the isolation rate of quinolone-resistant Camplyobacter in different production systems; </li>
<li> Determine the effect of quinolone use in poultry on the development and persistence of resistant Campylobacter using laboratory infection models; and </li>
<li> Establish an extension and education program to provide producers with science-based iknowledge on prudent use of antibiotics in food produsing animals. </li></ol></p>
Once we have accomplished the work proposed in this application, we will have a better understanding of which factors or management practices contribute to the development and persistence of resistant Campylobacters in poultry. </p>

More information

In spite of the widely appreciated magnitude of the problem associated with quinolone resistance, little is known about the factors that affect the development and persistence of resistant Campylobacter in poultry. Lack of this information has hampered the design and implementation of farm-based strategies to prevent the occurrence of quinolone resistance. <P>
The purpose of this project is to use an integrated approach to examine the development and persistance of quinolone-resistant Campylobacter in the poultry reservoir. </p>
As a result of this study effective and practical intervention strategies may be developed to minimize the level of quinolone resistance in the poultry production environment. </p>
Organic farms (no exposure to antibiotics) and integrated operations will be surveyed to determine the difference in quinolone resistance rates. Different types of poultry farms including broiler chickens and meat turkeys will be surveyed to determine if the resistance rates are related to management factors. A laboratory infection model will be used to monitor the development of quinolone-resistant Campylobacter in poultry and to examine how long quinolone resistance persists in campylobacters after the selection pressure is withdrawn from poultry. A variety of extension and education programs and activities will be used to disseminate the knowledge to producers and veterinarians.</p> <p>
In this project, ten integrated and 5 organic poultry farms (broiler and turkey) were surveyed for the prevalence of antibiotic resistant Campylobacter. Totally, 694 Campylobacter isolates were obtained and tested for susceptibilities to ampicillin, tetracycline, gentamicin, kanamycin, clindamycin, erythromycin, ciprofloxacin, norfloxacin, and nalidixic acid using the standard agar dilution method. </p>
In general, high resistance rates were associated with integrated operations. Specifically, the resistance rates to fluoroquinolone antimicrobials were 46% and 67% for integrated broiler and turkey farms, respectively, while the fluoroquinolone resistance rates for organic broiler and turkey farms were 0% and 2%, respectively. </p>
These findings clearly showed the differences in antibiotic resistance rates between different production systems and suggest that the differences are the consequences of antibiotic usages in integrated operations. </p>
To determine if fluoroquinolone treatment directly affected the resistance rates, treatments of Campylobacter-infected chickens with enrofloxacin were conducted in laboratory settings to monitor the development of resistant Campylobacter. The treatment transiently reduced the shedding of Campylobacter, but did not eradicate Campylobacter from the chickens. The rate of Campylobacter shedding recovered rapidly and reached the pre-treatment level three days after the cessation of the treatment. </p>
Drastic increases in the resistance to ciprofloxacin were detected with isolates derived from the treated chickens. In fact, nearly all of the isolates from the two FQ-treated groups showed MICs of more than 32 ug/ml. Sequence analysis of the gyrA gene showed that the Thr-86-Ile mutation was linked to high-level resistance to ciprofloxacin (MIC>32), while Asp-90-Asn mutation and Thr-86-Lys mutation were associated with intermediate-level resistance. Inactivation of the CmeABC efflux pump resulted in more than 21-fold decrease in resistance in the presence of gyrA mutations, indicating that the efflux pump is important for fluoroquinolone resistance.</p>
These results indicate that use of fluoroquinolones in chickens can rapidly select for resistant Campylobacter. To promote the prudent use of antibiotics on poultry farms we organized multiple workshops and continuing education programs, including Layer Health Management School, Poultry Health Management School, Broiler Health Management School, Poultry Health Management School, and Turkey Health Management School. These workshops focused on poultry health (including antibiotic resistance) for poultry producers throughout the Midwest. </p>
In addition, we also addressed antibiotic resistance issue with local poultry producers in conjunction with the Ohio Poultry Association Annual Meeting and periodically gave updates on the research at the poultry health forum. To reach the 4-H community, Dr. Morishita spoke on poultry health and antibiotic usage at 4-H regional poultry health fairs held annually. </p>
Our research results were also presented to the national and regional audience of poultry producers, veterinarians, and other poultry professional. </p>
Our findings indicate that treatment of chickens with enrofloxacin is a significant risk factor for fluoroquinolone-resistant campylobacter and the rate of resistance is influenced greatly by management practices.</p>
The information is useful for the design of intervention strategies to control the transmission and spread of antibiotic resistant Campylobacter. </p>

Zhang, Qijing
Iowa State University
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