Molecular Characterization of Extensively Drug-Resistant Pasteurella multocida Isolated From Apparently Healthy and Diseased Chickens in Egypt

Pasteurella multocida is a significant pathogen causing fowl cholera, a highly contagious disease of worldwide economic importance. Indiscriminate use of antimicrobials accelerates the emergence of resistance that represents a serious challenge for controlling P. multocida infection. In this study, the prevalence of P. multocida in apparently healthy and diseased chickens, capsular genotyping, antimicrobial resistance patterns and some resistance genes were determined. Lung, trachea, bone marrow and spleen samples were collected from 200 diseased and 100 apparently healthy chickens from ten layers and broilers commercial flocks for isolation of P. multocida. Confirmatory identification was done using P. multocida specific Polymerase chain reaction (PM-PCR) and multiplex PCR for capsular genotyping. P. multocida isolates were additionally tested for pathogenicity in mice. Antimicrobial resistance patterns towards 18 antimicrobials and detection of tetH, Bla(ROB1), aphA-1 and ermX genes were determined. P. multocida isolates were recovered from 10% of the diseased chickens and 4% of apparently healthy layers. All isolates were capsular type A, and susceptible to only one or two antimicrobial classes. Extensively drug resistance was found to gentamicin, ampicillin, erythromycin and trimethoprim/sulphamethoxazole, tobramycin, colisitin, penicillin, cefotaxime, chloramphenicol and doxycycline. Low resistance level was observed to ofloxacin (12.5%) and neomycin (41.67%). All isolates harbored tetH, followed by aphA-1 (70.83%) and Bla(ROB1) (8.3%). The obtained findings warrant attention to the emergence of extensively drug-resistant P. multocida from apparently healthy and diseased chickens. Consequently, prudent use of antimicrobials to treat infected birds efficiently, changing the utilization of antimicrobials in chicken feed both for prophylaxis and growth promotion is mandatory. (C) 2020 PVJ. All rights reserved