engleski

Prevalence of antimicrobial resistance genes in Escherichia coli longitudinally isolated from a broiler breeder farm

Antimicrobial resistance poses a great threat to the animal and human health. Despite the regulations for the usage of antibiotics in poultry farming, many farms excessively use them, which leads to the development of multidrug-resistant bacterial strains. Avian pathogenic Escherichia coli (APEC) is an extraintestinal pathotype, genetically very similar to uropathogenic and neonatal meningitis-associated E. coli, which cause problems in human population. The aim of this research was to determine the prevalence of the acquired resistance genes in APEC strains longitudinally isolated from four broiler breeders’ flocks that had severe problems with colibacillosis. Implementation of the autogenous E. coli vaccine to the immunoprophylaxis program in the Flocks 2, 3 and 4, significantly improved the performance rates and decreased the need for the antibiotic application. The daily mortalities on the studied farm were regularly pathomorphologically examined, and swabs from the bone marrow, liver, lungs, oviduct and peritoneum were bacteriologically examined. Identification of E. coli was confirmed by using MALDI-TOF MS. Afterwards, one strain per chicken from each flock was selected for whole-genome paired-end sequencing using NovaSeq, Illumina. The study included 10, 14, 13 and 14 isolates from four consecutive flocks, respectively. Genome sequences were analysed for the acquired resistance genes using ResFinder tool. The detected genes were aac(3)-VIa, aadA1, aadA2b, aph(3’’)-Ib, aph(3)-IIa, aph(6)-Id, blaCMY-2, blaCMY-38, blaMIR-2, blaMIR-6, blaTEM-1A, blaTEM-1B, blaTEM-1C, blaTEM-40, blaZEG-1, catA1, cmlA1, dfrA5, dfrA14, qnrB19, sul1, sul2, sul3, tet(A) and tet(B). Resistance genes for the class of beta-lactams showed highest prevalence in all flocks (50-100%). Also, 19, 61% of the isolates carried one, while 58, 82% carried two or more resistance genes. The results showed highest level of the resistance genes in Flock 2. In the first two flocks antimicrobial classes were more heterogenous, while the last two flocks showed less heterogenicity and increased prevalence of tetracycline resistance genes, which were most commonly used as therapy. As resistance and virulence-associated genes are mostly located on mobile genetic elements and therefore are easily transferable among bacteria, APEC strains can act as important reservoirs for both animal and human bacterial microflora. Thus, continuous monitoring of E. coli strains on poultry farms could help improve control of multidrug-resistant strains.

Escherichia coli, APEC, poultry, antimicrobial resistance, whole-genome sequencing

nije evidentirano