ABSTRACT
The purpose of this study was to investigate the tetracycline resistance in Trueperella pyogenes isolates from bovine samples in Burdur, Turkiye, and assess 16 tetracycline-resistance genes distribution among the isolates. Forty-nine T. pyogenes isolates were phenotypically characterized for anti-microbial resistance to doxycycline, oxytetracycline and tetracycline by disc diffusion method. Presence of tetracycline genes of T. pyogenes was investigated by multiplex and singleplex polymerase chain reaction. Our results indicated that 87.80% and 42.86% of the isolates were resistant to tetracycline and oxytetracycline, respectively, and the rate of resistance to doxycycline was 6.12%. Total of 21 (42.85%) were carrying tetracycline-resistance genes and tet(A) was present in 12 (24.49%) isolates; whereas, the tet(W) gene was identified in 9 (18.37%) and 2 (4.08%) of the isolates carried both tet(A) and tet(W), respectively. The study indicated antibiotic resistance patterns of tetracycline agents and links to the tet-genes among T. pyogenes were detected. It makes it worthwhile that this is the first report for detection of tet(A) gene in T. pyogenes.
ABSTRACT
Avian pathogenic Escherichia coli (APEC) causes colibacillosis, the disease with the highest economic loss for the broiler industry. However, studies focusing on the prevalence and population structure of APEC in the broiler production pyramid are scarce. Here, we used genotyping and serotyping data to elucidate the APEC population structure and its changes in different broiler production stages along with whole-genome sequencing (WGS) in a subset of APEC isolates to determine transmission patterns amongst dominant APEC sequence types (STs) and characterize them in detail. Comparison of genotypes encountered in both APEC and avian fecal E. coli (AFEC) provided further insights. Overall, APEC-related mortality, as the proportion of the total sampled mortality in the broiler production, was high (35%), while phylogroup C and serogroup O78 were predominant amongst APEC isolates. We found a low (34.0%) and high (53.3%) incidence of colibacillosis in chicks and end-cycle broilers, respectively, which may be related to a shift in APEC genotypes, suggesting a trend from commensalism to pathogenicity across different broiler production stages. Despite considerable APEC genotypic diversity, there was substantial genotype overlap (40.9%, overall) over the production stages and convergence of STs to the four clusters. Within these clusters, WGS data provided evidence of clonal transmission events and revealed an enriched virulence and resistance APEC repertoire. More specifically, sequenced APEC were assigned to defined pathotypes based on their virulence gene content while the majority (86%) was genotypically multi-drug resistant. Interestingly, WGS-based phylogeny showed that a subset of APEC, which are cephalosporin-resistant, may originate directly from cephalosporin-resistant AFEC. Finally, exploration of the APEC plasmidome indicated that the small fraction of the APEC virulome carried by IncF plasmids is pivotal for the manifestation of the APEC pathotype; thus, plasmid exchange can promote pathogenicity in strains that are at the edge of the commensal and pathogenic states.