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The UK has approximately 10 million cattle (Veterinary Medicines Directorate 2011), and each year approximately 1.9 million of these cattle are affected by respiratory disease. A disease that is often complex, caused by viruses and/or bacteria, with as many as one-third of these infected with the Mycoplasma bovis pathogen (Nicholas and Ayling 2003). The welfare and economic effects of clinical cases of M. bovis on farming are therefore substantial and costs may be even more when morbidity associated with respiratory infection is considered. Apart from respiratory disease, M. bovis is also associated with other clinical signs, including mastitis, arthritis, meningitis, infertility, abortion and keratoconjunctivitis (Nicholas and Ayling 2003). Elimination of M. bovis is difficult and treatment with antimicrobials often has limited effect unless animals are treated early in the course of disease. In recent years, as much as 11 tonnes per annum of active antimicrobials have been sold for use in the UK cattle antimicrobial products, which includes all intramammary products (Veterinary Medicines Directorate 2011). With no commercial vaccines available in Europe, although use of autogenous vaccines has shown some success (Nicholas and others 2006), it is important to effectively target antimicrobial treatment to ensure prudent use of antimicrobials and to reduce the development of antimicrobial resistance. Between 2004 and 2009, in vitro minimum inhibition concentration (MIC) data for 45 M. bovis isolates have been determined for up to 13 antimicrobials.
Materials and methods
Forty-five epidemiologically unrelated M. bovis isolates from cattle were tested, as well as the National Collection of Type Cultures (NCTC) type strain (NCTC 10131); details are given in Table 1. Samples were previously submitted to the Animal Health and Veterinary Laboratories Agency for mycoplasma detection and identification by culture and molecular methods that include PCR and denaturing gradient gel electrophoresis (McAuliffe and others 2005). Isolates were subsequently stored …