Influence of Single Dose Enrofloxacin Injection on Development of Fluoroquinolone Resistance in Campylobacter jejuni in Calves

Abstract

Fluoroquinolone (FQ) resistance in a major foodborne bacterial pathogen, Campylobacter jejuni, derived from cattle has recently become prevalent and poses a significant public health concern. However, the underlying factors for this increase are not entirely clear. To evaluate the effect of enrofloxacin treatment on FQ-resistance development in C. jejuni, 35 commercial calves were equally divided into five groups (Groups 1–5) and were orally inoculated with FQ-susceptible (FQ-S) C. jejuni. Eight days later, Groups 4 and 5 were challenged with Mannheimia haemolytica via a transtracheal route to induce a respiratory disease; after 8 days, Groups 2, 3, 4, and 5 were injected subcutaneously with enrofloxacin (7.5 mg/kg for Groups 2 and 4, and 12.5 mg/kg for Groups 3 and 5). Colonization levels by FQ-resistant (FQ-R) and FQ-S Campylobacter in rectal feces were determined via differential culture throughout the experiment. Before oral inoculation with C. jejuni, only five calves were naturally colonized by Campylobacter, four of which were also colonized by FQ-R C. jejuni (three in Group 1 and one in Group 3). Soon after the oral inoculation, almost all calves in the groups became stably colonized by FQ-S C. jejuni (~3–6 log10 CFU/g), except that the four calves that were pre-colonized before inoculation remained positive with both FQ-R and FQ-S C. jejuni. Following enrofloxacin administration, C. jejuni colonization declined sharply and rapidly in all treated groups to undetectable levels; however, the vast majority of the animals were recolonized by C. jejuni at comparable levels 72 h after the treatment. Notably, no FQ-R C. jejuni was detected in any of the calves that received enrofloxacin, regardless of the drug dose used or disease status of the animals. The lack of detection of FQ-R C. jejuni was likely due to the localized high concentration of the antibiotic in the intestine, which may have prevented the emergence of the FQ-R mutant. These findings indicate that single-dose enrofloxacin use in cattle poses a low risk for selection of de novo FQ-R mutants in C. jejuni.

Growth kinetics and fitness of fluoroquinolone resistant and susceptible Campylobacter jejuni strains of cattle origin

“…In chickens, as soon as 24 h after treatment with FQ antibiotics (enrofloxacin, sarafloxacin, or difloxacin; typically given in drinking water for 5 days), FQ-R Campylobacter mutants were found in the feces of treated birds and gradually colonized the intestinal tract at high densities ( 34 , 56 , 57 ). In big contrast, our recent study with calves showed that a single dose s.c. enrofloxacin treatment (7.5 or 12.5 mg/kg) did not result in any detectable level of FQ resistance development from FQ-S C. jejuni inhabiting the intestine ( ~ 10 4–5 CFU/g feces) of calves ( 46 ). Similarly, therapeutic administration of neither oral (20 mg/kg daily for 7 days) nor subcutaneous (20 mg/kg daily for 1–7 days) enrofloxacin resulted in development FQ-resistance in C. jejuni NCTC 11168 following experimental inoculation of mice via oral gavage ( 69 ).…”

“…Cattle are a significant source of human Campylobacter infections, and there is a clear trend that FQ-R Campylobacter from cattle has become highly prevalent in recent years ( 7 , 15 , 62 , 63 ). Even though the selection pressure (use of FQs in cattle) may have contributed to the expansion of FQ-R Campylobacter , the actual impact of this factor appears to be rather low ( 32 , 44 , 46 , 64 ). In the current study, we examined the hypothesis that the fitness of FQ-R Campylobacter may have also played a role in the rise seen in FQ-R Campylobacter isolates of cattle origin.…”

“…Campylobacter -free rectal feces collected freshly and saved at −80°C during our previous investigation ( 46 ) was used as a bovine fecal extract in the current study. To confirm the Campylobacter -free status, fecal samples were plated on Mueller-Hinton (MH) agar (Difco, BD, Sparks, MD) plates containing Campylobacter growth supplement (SR084E; Oxoid, Basingstoke, England) and Preston Campylobacter selective supplement (SR117E; Oxoid).…”

“…Instead, ability to grow in MH agar containing 4 μg/mL ciprofloxacin (clinical resistance breakpoint per CLSI) was used as an indication of FQ-resistance in the present study. This method was used in many of our previous studies and shown to correlate well with the standard MIC-based resistance determination (32,34,40,46,50,51). Campylobacter jejuni strains (in glycerol stocks saved in freezers) were grown on MH agar at 42°C for 48 h under microaerobic conditions.…”

Zoonotic and antibiotic-resistant Campylobacter: a view through the One Health lens

“…Different from sheep production where the use of FQ antimicrobials is prohibited, FQs are used for the treatment and control of respiratory diseases in cattle [63]. The use of FQ antimicrobials could serve as a selection force for the spread of FQ-resistant Campylobacter, but a recent FQ treatment study suggested that subcutaneous injection of FQ antimicrobials did not result in the de novo development of FQ-resistant mutants from the inoculated FQ-susceptible C. jejuni in the cattle intestinal tract [64]. As explained by the authors, this might be due to the relatively low density of Campylobacter in cattle feces and the high concentration of the antimicrobial excreted into the intestine [65], which could have exceeded the mutant selection window and prevented the emergence of FQ-resistant mutants.…”