TDK conference 2016

Mycoplasma synoviae is associated with exudative tendinitis, infectious synovitis, respiratory tract infection, and eggshell apex abnormalities (EAA). M. synoviae occurs in chickens and turkeys, and may be transmitted both horizontally and vertically. With its worldwide distribution, wide pathogenic spectrum and increasing occurrence, M. synoviae has become a pathogen of economic relevance and research. Control of M. synoviae infection consists of three general aspects: eradication followed by prevention, vaccination or medication. Medication by antibiotics can reduce economic losses, however, in order to maximize treatment efficacy the antibiotic susceptibility profiles of the Mycoplasma strains involved should be predetermined.

A total of 20 M. synoviae strains isolated from chickens and turkeys originating from Hungary were tested in this study. A microbroth dilution method was performed on each strain, and the minimum inhibitory concentration (MIC) values were determined after 14 days. MIC50 values were defined as the lowest concentrations that inhibited the growth of 50% of the strains. The antibiotics examined were: enrofloxacin, difloxacin, doxycycline, oxytetracycline, chlortetracycline, tylvalosin, tilmicosin, tylosin, tiamulin, valnemulin, florfenicol, neomycin, spectinomycin and lincomycin. Lincomycin and spectinomycin were also applied in combination (1:2 ratio).

The MIC50values of the fluoroquinolones, enrofloxacin and difloxacin were 2.5 μg/ml and 5 μg/ml respectively. From the aminoglycosides spectinomycin had the MIC50value of 2 μg/ml while neomycin could not inhibit the growth of the 50% of the strains by the examined concentrations (MIC50 >64 μg/ml). The lincosamide lincomycin had a MIC50value of 1 μg/ml, while the combination with spectinomycin gave a higher value of 2 μg/ml. Among the tetracyclines doxycycline had a MIC50 value of 0.156 μg/ml followed by oxytetracycline 1 μg/ml and chlortetracycline 4 μg/ml. The phenicol florfenicol had a MIC50value of 8μg/ml. All three macrolides: tylvalosin, tylosin and tilmicosin showed low MIC50values of <0.25 μg/ml. Out of the pleuromutilins valnemulin had a MIC50 value of <0.039 μg/ml, while tiamulin 0.156 μg/ml.

In this study the most effective antibiotics were found to be the tetracyclines, macrolides and pleuromutilins against M. synoviae. Our results confirmed that increasing resistance could be observed in the cases of several antibiotics. These findings highlight the need for determination of antibiotic susceptibility of Mycoplasma species before treatment.