Monitoring Mycoplasma gallisepticum and Mycoplasma synoviae infection in breeder chickens after treatment with enrofloxacin

Three experimental strains of breeder chickens were accidentally exposed to Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS), presumably Fro m a newly introduced group of leghorn-type pullers. The experimental strain s subsequently became infected and were diagnosed positive for MG and MS by the serum plate agglutination (SPA) test and confirmed by the hemagglutina tion inhibition (HI) test and the polymerase chain reaction (PCR) of trache al swabs. Treatment with 10 mg/kg enrofloxacin via drinking water for 14 da ys was elected. Before and after initiation of treatment, MG and MS were mo nitored for changes by SPA, HI, PCR, and culture, with sampling intervals r anging from 1 wk to 7 wk. MG and MS SPA, HI, PCR, and culture were performe d at each sampling period, with the exception of weeks 1.0 and 6.5. Week 1. 0 included SPA and His for MG and MS. Week 6.5 included PCR and culture for MG and MS. The MG and MS SPA results were positive throughout the 29-wk tr ial period. MG HI titers declined until the last sampling, whereas the MS H I titers did not decline significantly. PCR for MG yielded only one positiv e result, which occurred before treatment. MS PCR remained positive through out the trial period. MG was never isolated from any sample; however, one M S organism was isolated during treatment. The treatment regimen was effecti ve for MG on the basis of PCR results. Treatment with enrofloxacin did not eliminate SPA reactions during the 29-w k trial period. MG HI titers remained in the suspicious range throughout th e remainder of the trial period. Four weeks after the treatment ended, MG H Is were reduced by similar to 40%, with MS HIs remaining high throughout th e 23-wk period. PCR appeared to be a sensitive and specific test on the bas is of correlation with HIs. On the basis of the isolation of MS during trea tment and continued subsequent PCR positive reactions, the treatment for MS with enrofloxacin was not as efficacious as for MG.