Isolated from broilers in a poultry farm of perm krai: А 14-year study

Abstract

Sanitary and anti-epizootic measures in poultry industry should restrict spread and circulation of antibiotic-resistant bacteria, including pathogens which are the causative agents of epidemic diseases. This paper is our first report on prevalence and antibiotic resistance of enterobacteria in a commercial poultry flock population during a 14-year period with an assessment of the effectiveness of the most common fluoroquinolone- and colistin-containing veterinary medicines. Our goal was to compare species diversity and the antibiotic resistance of enterobacterial strains isolated from cross Ross 308 broiler chickens (Gallus gallus) in a large poultry complex (JSC PRODO Perm Poultry Farm, Perm Krai). Dead embryos and trachea, lungs, heart, liver, spleen, femur and tibia bones collected from slaughtered broilers were the pathomaterial (995 samples in 2004-2009, and 991 samples in 2010-2017). The organs of healthy broilers served as a control. In special experiments, we assessed the effectiveness of veterinary drugs used against certain pathogens. It was found that the frequency of Enterobacteriaceae family members remained stably high during the whole observation and significantly exceeded that of gram-positive microorganisms (p < 0.00001). In 2010-2017, bacterial contamination was higher in heart (p < 0.05) and spleen (p < 0.01), while the rate of infected dead embryos averaged 25 % and was lower (p < 0.05) compared to 2004-2009. Escherichia coli dominated, and Proteus mirabilis was a subdominant species. The prevalence of avian pathogenic E. coli (APEC) in the microbial community did not change, Proteus isolates (p < 0.0001) increased, and salmonella decreased (p < 0.05), the prevalence of other enterobacteria did not differ significantly. The prevalence of antibiotic-resistant E. coli was multidirectional: the ciprofloxacin-resistant strains increased from 47.4 to 75.9 % (p < 0.0005), whereas the amikacin-resistant strains decreased from 32.8 to 16.4 % (p < 0.0001). It was shown that Coliflox (NEC Agrovetszashchita SP, LLC, Russia) which contains maximum dosage of colistin and enrofloxacin is the most active among four studied colistin-containing medicines. Further down medicines are Vitrocil (Interchemie werken De Adelaar BV, Netherlands), which contains 10 times less colistin and 2 times less enrofloxacin, Pulmosol® (VIK — Animal Health LLC, Belarus) and Aquaprim (SP Veterinaria, SA, Spain) with 1.1 million and 400,000 IU colistin, respectively. Pulmosol® and Aquaprim, lacking of fluoroquinolones, showed the least activity (37.5 and 35.7 % of resistant E. coli, respectively, and 50.0 and 37.5 % of resistant Proteus spp.). Thus, combined veterinary medicines containing enrofloxacin had the highest activity against enterobacteria, but the effectiveness of these drugs has decreased in recent years. The long-term use of fluoroquinolones as dietary additives to prevent infections among poultry seems to be a risk factor leading to the selection of resistant strains.