Could honey bees signal the spread of antimicrobial resistance in the environment?

The honey bee has long been known to be a bioindicator of environmental pollution and the use of antimicrobials in the beekeeping industry is strictly regulated. For these reasons, this paper was aimed to evaluate for the first time the role of Apis mellifera as a possible indicator of environmental antimicrobial resistance (AMR). The study isolated and analysed the resistance patterns of Enterobacteriaceae from a pool of honey bee guts located in five different environmental sites (ES), where different antimicrobial selective pressures were hypothesized. In all, 48 isolates were considered for identification and underwent analyses of AMR to ampicillin, amoxicillin/clavulanic acid, cefazolin, ceftazidime, tetracycline, imipenem, enrofloxacin, amikacin and trimethoprim/sulfamethoxazole. In all, 12 isolates out of 48 (25%) showed resistance to at least one antimicrobial drug. There were no significant differences between the resistance rates observed in the ESs, even if the highest percentage of resistance was found in ES4. Resistances to amoxicillin/clavulanic acid resulted significantly higher than those detected towards the other antimicrobials. Amoxicillin/clavulanic acid is not commonly used in beekeeping but it is extensively used in animals and in humans, suggesting an environmental origin of this resistance and supporting the hypothesis that honey bees could be used as indicators of AMR spread in the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, a possible role of honey bees as indicator of environmental antimicrobial resistance is hypothesized. Enterobacteriaceae were isolated from bees living in different environmental sites (ES) where different antimicrobial selective pressures were hypothesized. Even if no differences between the resistances in the five ES were observed, the resistance rates for amoxicillin/clavulanic acid, compared to other antimicrobials, were significantly higher. Since amoxicillin/clavulanic acid is not used in beekeeping but it is extensively used in animals and in humans, an environmental origin of this resistance is suggested that supports our hypothesis.