The persistence of fluoroquinolone-resistant Campylobacter in poultry production.

Resistance to antimicrobials is a growing crisis in clinical medicine, and it is generally recognized that misuse and overuse in any sector contributes to this burden. Antimicrobial use in food animal production is an area of concern because the on-farm selection of antimicrobial-resistant zoonotic pathogens can lead to human exposure and infection via various pathways, including meat and poultry products. Fluoroquinolone use in poultry production selects for fluoroquinolone-resistant Campylobacter populations and is associated with an increase in fluoroquinolone-resistant Campylobacter infections in humans via poultry exposure (Gupta et al. 2004, 2005). Campylobacter is an important foodborne zoonotic pathogen causing enteritis and diarrhea (campylobacteriosis). Campylobacter infection is also associated with a number of rare neuropathologic sequelae, including Guillain-Barre syndrome (Hughes et al. 1999). In the United States, Campylobacter is the most common cause of bacterial diarrhea, with over a million people estimated to be affected annually [Centers for Disease Control and Prevention (CDC) 2005]. Campylobacteriosis is typically self-limiting, with symptoms rarely lasting more than 10 days (Butzler 2004; CDC 2005); however, it can be fatal in more vulnerable populations (Djuretic et al. 1996; Manfredi et al. 1999; Tee and Mijch 1998). Indeed, antimicrobial therapy is essential for elderly, pregnant, and immunocompromised patients for whom hydration and electrolyte maintenance may be insufficient (Allos 2001). Until recently, fluoroquinolones were regularly prescribed for those requiring antimicrobial therapy. However, a sharp increase in the prevalence of fluoroquinolone-resistant Campylobacter, shown to occur in parallel with the use of fluoroquinolones in U.S. poultry production, has limited fluroquinolones’ effectiveness in the clinical setting (Allos 2001; Collignon 2005; Gupta et al. 2004). Immunocompromised patients with Campylobacter bacteremia often require a prolonged course of multiantimicrobial therapy (Tee and Mijch 1998); therefore, the loss of fluoroquinolones as an effective therapeutic has become a threat to these patients. Based on a risk assessment of the contribution of fluoroquinolone use in poultry production to fluoroquinolone-resistant Campylobacter infections in humans, the Food and Drug Administration (FDA) suspended all fluoroquinolone use in poultry production as of 12 September 2005 (FDA 2000). The goal of this policy is to eliminate on-farm selection of fluoroquinolone-resistant Campylobacter and thereby reduce human exposure via food to these organisms. However, this policy’s efficacy may be limited by stable reservoirs of fluoroquinolone-resistant Campylobacter strains in and around poultry production facilities. These reservoirs can serve to sustain resistant Campylobacter in poultry environments, even after the cessation of on-farm fluoroquinolone use (Bull et al. 2006; Moore et al. 2006). Furthermore, some studies indicate that fluoroquinolone-resistant Campylobacter isolates may actually be more fit than the wild-type with respect to poultry colonization (Zhang et al. 2006). Therefore, to better assess this policy’s efficacy, it is essential to monitor the prevalence of resistant strains in poultry flocks, production facilities, consumer poultry products, and human infections. If resistant strains continue to persist in spite of the fluoroquinolone ban, it may be necessary to implement other measures in order to reduce fluoroquinolone-resistant Campylobacter populations. Previously, we reported that poultry products from two conventional producers were more likely to be contaminated with fluoroquinolone-resistant Campylobacter than products from producers who claimed to use no antibiotics (Price et al. 2005), even though both conventional producers had announced discontinuation of fluoroquinolone use 1 year before the study. Because of the relatively short period of time between this announcement and our analysis, we undertook the current study of products for an additional 3 years (i.e., 4 years beyond the point at which these two companies committed to stop using fluoroquinolones).