Correlation between Resistance to Ciprofloxacin and Roxarsone Found in Campylobacter Species

Introduction: As bacteria develop resistance to many available antibiotic treatments, cross-resistance becomes a major concern. Campylobacter is known to possess a multidrug efflux pump that contributes to resistance of unrelated antibiotics. Some Campylobacter strains carry arsenic resistance genes that encode an efflux pump and a membrane permease, which could potentially act as alternate pathways for antibiotic resistance.

Purpose: To examine the prevalence of antibiotic and arsenic resistance in Campylobacter isolated from retail conventional and organic chicken and to determine any correlation between arsenic resistance and antibiotic resistance.

Methods: Sixty-five Campylobacter isolates from retail chickens, organic and conventional, were screened for resistance to arsenic and six antibiotics. Arsenic resistance was determined by minimum inhibitory concentrations for arsenate, arsenite, and roxarsone via agar dilution method and antibiotic resistance was determined using the disc diffusion method (following CLSI standard procedures).

Results: It was determined that all isolates were resistant to cephalothin and susceptible to gentamicin, erythromycin, and chloramphenicol. Isolates varied in resistance to tetracycline and ciprofloxacin, 34% and 26%, respectively, were resistant. Ciprofloxacin resistance was significantly correlated with increased roxarsone resistance (P = 0.0022), while tetracycline resistance was not significantly correlated with any arsenic resistance. 

Significance: Cross-resistance is a major concern for the growing threat of antibiotic resistance. The correlation between ciprofloxacin resistance and roxarsone resistance could be an indication of a cross-resistance mechanism within Campylobacter.