Antibiotic Resistance of Enterococcus faecalis Isolated from Gastrointestinal Tract of Broiler Chickens after Propolis and Bee Pollen Addition

One of the safety aspects of antimicrobials (propolis and bee pollen) use in poultry farms as growth promoters is higher susceptibility of gastrointestinal microorganisms to antibiotics used for human treatment. Enterococci belong to the normal microbiota of gastrointestinal tract of chickens and are widely distributed in nature, but they are not generally recognized as safe (GRAS). Poultry enterococci carrying antimicrobial resistance genes may not only transfer these genes to other, possibly pathogenic, bacteria in the chicken gut, but upon transfer to zoonotic bacteria they also may pose a human health hazard. Antibiotic resistance prevalence of E. faecalis isolates found in the crop was subsequently found in the ileum and caecum within each group of broiler chickens. No resistance of E. faecalis isolates was found against vancomycin and teicoplanin. Intermediate resistance to erythromycin in the most E. faecalis isolates from gastrointestinal tract of broiler chickens with propolis supplement in their diet was eliminated. Our results suggest the probability of synergism effect of propolis and also bee pollen with some tested antibiotics against E. faecalis isolates.