In vitro Evaluation of Various Antimicrobials against Field Mycoplasma gallisepticum and Mycoplasma synoviae Isolates in Egypt

Abstract

Among many avian mycoplasmas, Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are recognized as the main etiological agents of respiratory diseases and infectious synovitis in chickens and turkeys causing tremendous economic losses worldwide. Therefore, proper treatment is promoted for the control of these diseases. This study was the first in Egypt to evaluate the in vitro efficacy of various antimicrobials against field MG and MS isolates recovered from chicken and turkey flocks using both conventional microdilution and quantitative real-time PCR (qRT-PCR) assays. Totally, 47 mycoplasma isolates were recovered from 160 collected tracheal samples (29.4%). Of these, 44 MG (27.5%) and 3 MS (1.9%) were identified using conventional and molecular assays. The in vitro susceptibilities of 4 representative mycoplasma isolates (3 MG and one MS) to 8 antibiotics and 4 essential oils were investigated. The tested isolates showed various susceptibilities to tested antimicrobials. Toldin CRD, followed by clove, cumin and cinnamon oils were commonly effective against both MG and MS clinical isolates with MIC values ranging from 0.49 to 15.63 {micro}g/mL. Similarly, tylvalosin was the most active antibiotic against MG and MS isolates with the lowest MIC values (0.015-0.03 {micro}g/mL). DNA copies of both MG mgc2 and MS vlhA genes were markedly decreased upon treatment with majority of tested antimicrobials confirming their effectiveness as was also evaluated by conventional MIC results. In conclusion, Toldin CRD and tylvalosin were found to be the most effective antimicrobials in this study, which will contribute in controlling avian mycoplasma infections.\n\nAuthor SummaryAvian mycoplasmosis is considered as one of the most prominent economic problems in the commercial poultry industry worldwide. Antimicrobial therapy is the most effective tool for treatment of mycoplasmas. Owing to the side effects of antibiotics and the development of resistance to the currently used drugs, an increased emphasis on the use of alternative antimicrobials is of utmost importance. Here, we evaluate the in vitro inhibitory effects of some essential oils and various commercial antibiotics against Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) field isolates using micro-broth dilution method and qRT-PCR assays. We found that toldin CRD, followed by clove, cumin and cinnamon oils were effective against both MG and MS clinical isolates. Similarly, tylvalosin was the most active antibiotic against MG and MS isolates. We also found that DNA copies of both MG mgc2 and MS vlhA genes were markedly decreased upon treatment with majority of tested antimicrobials. Our study provides new insights into the control of avian mycoplasma infections.