23S rRNA and L22 ribosomal protein are involved in the acquisition of macrolide and lincosamide resistance in Mycoplasma capricolum subsp. capricolum.

Mycoplasma capricolum subsp. capricolum (Mcc) is one of the causative agents of contagious agalactia, and antimicrobial therapy is the most commonly applied measure to treat outbreaks of this disease. Macrolides and lincosamides bind specifically to nucleotides at domains II and V of the 23S rRNA. Furthermore, rplD and rplV genes encode ribosomal proteins L4 and L22, which are also implicated in the macrolide binding site. The aim of this work was to study the relationship between mutations in these genes and the acquisition of macrolide and lincosamide resistance in Mcc. For this purpose, in vitro selected resistant mutants and field isolates were studied. This study demonstrates the appearance of DNA point mutations at the 23S rRNA encoding genes (A2058G, A2059G and A2062C) and rplV gene (Ala89Asp) in association to high minimum inhibitory concentration values. Hence, it proves the importance of alterations in 23S rRNA domain V and ribosomal protein L22 as molecular mechanisms responsible for the acquisition of macrolide and lincosamide resistance in both field isolates and in vitro selected mutants. Moreover, these mutations enable us to provide an interpretative breakpoint of antimicrobial resistance for Mcc at MIC 0.8 μg/ml.