**2.** *Mycoplasma bovis***: Key Facts**

*Mycoplasma bovis*(*M. bovis*) is most often considered to cause caseonecrotic pneumonia, mastitis and arthritis [6,7]. However, cases of infectious keratoconjunctivitis, suppurative otitis media, meningitis, decubital abscesses, endocarditis and reproductive disorders have been associated with *M. bovis* [7–10]. Most importantly *M. bovis* is one of the causes of BRD with other aetiological agents, both bacterial and viral [11,12].

*M. bovis* is one of 13 species of mycoplasmas diagnosed in cattle; however, not all of them cause serious diseases, and some may even constitute normal flora of the bovine respiratory tract. For example, the most important mycoplasma in bovine severe respiratory diseases is the previously mentioned *Mycoplasma mycoides* subsp. *mycoides*. *Mycoplasma bovigenitalium* is generally associated with bovine reproductive disorders, while *Mycoplasma bovoculi* has been isolated from infectious keratoconjunctivitis in cattle [3]. *M. bovis* infections are non-zoonotic; however, substantial economic and cattle health and

welfare impacts are felt worldwide [3]. *M. bovis* affects all age groups of cattle (prewean, postwean, neonate and adult) and all cattle sectors such as beef, milk or rearing [3]. *M. bovis* can persist in a herd for very long periods of time, with the possibility of pathogen shedding by the infected animals for a few weeks to several months [13,14]. The evolutionary absence of a cell wall in principle makes *M. bovis* resistant to penicillins and cephalosporins [3,4]. Moreover, in vitro studies on *M. bovis* field isolates show increasing trends in antimicrobial resistance, including tetracyclines and even newer generation macrolides considered effective against *M. bovis* infections [5,15–18]. *M. bovis* infections are usually characterized by chronic course and are difficult to treat successfully [3]. One recent in vivo study has shown an efficacy of treatment of the *M. bovis* pneumonia in calves using enrofloxacin given alone, unlike the combination therapy with co-administration of flunixin meglumine, a nonsteroidal anti-inflammatory drug or pegbovigrastim (immunostimulator), which rather exacerbated the disease. However, it should be remembered that fluoroquinolones, although effective in this case, should be used as antimicrobials of last resort [19]. Some experimental *M. bovis* vaccines have been shown to be immunogenic and protective; however, currently no commercial vaccines are available in Europe with only some autogenous vaccines in use in the United States and Great Britain [20–22].
