| Abstrakt: |
Mycoplasma synoviae (M.s.) is a pathogenic mycoplasma with great economic impact in commercial poultry due to disease problems. In cases with severe clinical signs antibiotic treatment is given to reduce the impact of disease in the flock. Several antimicrobials are registered for treatment of M.s. infections. To allow more prudent use of antimicrobials, information on antimicrobial susceptibility profiles of M.s. is important. Recent publications on antimicrobial susceptibility (AMS) of M.s. are scarce. This study was performed to examine the AMS of M.s. isolates obtained from Dutch poultry in the years 2001 to 2018. The collection consists of 48 M.s. isolates from commercial and backyard poultry (chickens and turkeys) from the Netherlands, obtained between 2001 and 2018. The identity of M.s. isolates was confirmed by PCR. Minimal inhibitory concentrations (MICs) were determined by broth microdilution using commercially available MIC plates. Mycoplasma Experience (ME) broth was used as growth medium, and a standard dilution of culture was added to each well so that 0.5x10e3-10e5 CCU per ml were delivered in a final 50 ml volume. Plates were sealed, incubated under aerobic conditions at 37°C, and after seven days minimal inhibitory concentrations (MICs) were read. The in vitro susceptibility to four different antimicrobials was examined. For each antimicrobial agent the range of MIC-values, the MIC50- and MIC90-values were calculated. Most of the susceptibilities were determined as lower as or equal to the lowest concentration tested or higher than the highest concentration tested, except for oxytetracycline. Results show lowest MIC values for tylosin (MIC50 of ≤0.5 and MIC90 of ≤0.5 μg/mL, respectively), tilmicosin (MIC50 and MIC90 both being ≤4 μg/mL), and tiamulin (MIC50 and MIC90 both being ≤0.5 μg/mL). Susceptibility for oxytetracycline comprised more MIC-values (MIC50 of 4 μg/mL and MIC90 of 8 μg/mL, respectively). Results show good susceptibility to the antimicrobials tested, except for oxytetracycline. Further research into the specific genes for tetracycline resistance is recommended.There is a great need for the development of a standardized and harmonized method for M.s.-specific AMS testing, which also may contribute to establish specific clinical breakpoints. Therefore, currently it is not possible to interpret the MIC-values into treatment advises for the field. [ABSTRACT FROM AUTHOR] |
