Prevalence, Identification and Antibiotic Resistance of Isolates from Chickens in Poland.

The Gram-negative bacterium is part of the normal avian respiratory, intestinal and reproductive tract microflora and can be transmitted horizontally and vertically. With the coexistence of other relevant factors, becomes an opportunistic pathogen, economically damaging to the poultry industry. This bacterium's prevalence and molecular epidemiology were investigated, and the antimicrobial treatment options for infection in chicken flocks in Poland were assessed. Tracheal samples from 182 flocks were collected between April 2022 and March 2023. The bacterial prevalence was determined by PCR targeting the B gene and 16-23S rRNA. was identified by matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF) after culturing and PCR amplification. Isolates' susceptibility to 11 antimicrobials was assessed with a disc diffusion test. Isolates were also tested for B, A and virulence genes and , A, B and H antibiotic resistance genes by PCR. Forty-one flocks (22.5%) were positive through PCR. Antibiotic resistance was most frequently observed against tilmicosin, tylosin, enrofloxacin, amoxicillin, tetracycline and doxycycline. Multiple resistance to at least eight antibiotics occurred in 20% of isolates and to at least four in 100%. The occurrence of B was noted in 100%, A was detected in 89%, and A was found in 14% of positive samples. The B gene was present in 61.0% of positive samples, H was in 36.0%, A was in 16.7%, and was in 5.6%. Significant differences were found in isolates related to the presence of the virulence genes GtxA and gyrB and the presence of resistance genes ( < 0.05) associated with resistance to tetracyclines, β-lactams and aminoglycosides. The continued rise in the resistance of to a broadening range of antibiotics is a major problem for the poultry industry worldwide, as well as for public health. The findings of this study may expand the knowledge of the pathogenicity of in poultry.