Abstract
Bovine respiratory disease (BRD) is common in calves in Algeria, but to date, Mycoplasma bovis has never been monitored as a potential etiological agent. Here, to assess the presence (direct detection) and circulation (indirect detection) of M. bovis, broncho-alveolar lavage fluids (BALF) and serum samples were collected from 60 veal calf farms in Algeria. A commercial ELISA kit (ID Screen(®) ELISA) was used to screen for the presence of specific antibodies against M. bovis in 351 blood sera collected from both diseased and healthy calves, and 69% (241 sera) tested positive. BALFs from the 176 diseased calves were used to screen for M. bovis by real-time-PCR (rt-PCR), and 102 (58%) tested positive. A non-exhaustive set of 53 clones were isolated from 44 calves and further subtyped using polC gene sequencing. No predominant subtype was found, and two clones exhibited a new subtype. Fourteen clones were further characterized by multilocus sequence typing, and results showed a high degree of genetic diversity, with some clones having new alleles and subtypes. The minimum inhibitory concentrations (MICs) of 5 antimicrobials regularly used to treat BRD was determined on 45 clones. Susceptibility profiles showed very broad diversity, confirming the variety of clones actively circulating. We detected clones with high MICs, including increased MICs of enrofloxacin (n = 5). This is the first study to report the presence of M. bovis in Algeria in calves with BRD. This research also finds broad genetic and phenotypic diversity in the actively circulating isolates.