Antibiotic sensitivity of Mycoplasma bovis and other respiratory pathogens isolated from pneumonic lung samples in a calf rearing unit in Turkey

Abstract

Mycoplasma bovis, a serious cause of bovine respiratory disease often associated with other bacteria and viruses, is prevalent worldwide including Turkey. It is difficult to control because antibiotics are becoming increasingly ineffective and commercial vaccines are not available. The aims of this study were to detect infective agents causing respiratory disease in a calf rearing unit in Turkey to determine antibiotic susceptibilities of the strains isolated and to carry out molecular typing. In diseased lungs from calves dying of pneumonia we found M. bovis to be present in all samples of acute and chronic diseased tissue. Mannheimia haemolytica was detected mostly in chronic tissue (39 %) while the reverse was true for Pasteurella multocida with most isolations from acute tissue (25 %). High minimum inhibitory concentrations (MIC) were seen for most antibiotics against M. bovis: tylosin, tilmicosin, erythromycin, chloramphenicol, oxytetracycline and ciprofloxacin with MIC50s of >32 μg/ml, intermediate-sensitivity to florfenicol, spectinomycin, danofloxacin, enrofloxacin and marbofloxacin with MIC50 of 8 μg/ml, and susceptible to lincomycin, clindamycin and tulathromycin with MIC50 of 1, 0.25, 0.25 μg/ml respectively. While all tested isolates of both M. haemolytica and P. multocida were resistant to gentamicin, P. multocida isolates showed resistance rates of 100 % to erythromycin and tylosin, 88 % to trimethoprim-sulphametoxasol, 75% to tetracycline and tilmicosin, 50 % to tulathromycin and enrofloxacin. The resistance rates of M. haemolytica isolates were 90 % to erythromycin, 75 % to tylosin, 64 % to tetracycline, 55 % to trimethoprim-sulphametoxasol, 36 % to tilmicosin, 18 % to enrofloxacin, 9 % to marbofloxacin, florfenicol, ampicillin and penicillin. Finally, M. bovis could be divided into two distinct genetic clusters by molecular typing tests. *Correspondence to: Nıcholas RAJ, The Oaks, Nutshell Lane, Farnham Surrey, UK, E-mail: robin.a.j.nicholas@gmail.com