The role of Mycoplasma synoviae in commercial layer E. coli peritonitis syndrome and Mycoplasma gallisepticum intraspecific differentiation methods
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Mycoplasmas are bacteria that belong to the class Mollicutes. Mycoplasmas are found in humans and animals, and the species that were recognized as pathogens of domestic poultry include Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) in chickens and turkeys, and Mycoplasma meleagridis and Mycoplasma iowae in turkeys. MS is an important pathogen of domestic poultry, and is prevalent in commercial layers. During the last decade Escherichia coli (E. coli) peritonitis became a major cause of layer mortality. Commercial layers at the onset of lay were challenged through the respiratory tract with a virulent MS strain or a virulent avian E. coli strain, or both. A significant E. coli peritonitis mortality was detected in the MS plus E. coli challenged group, and severe tracheal lesions and moderate body cavity lesions were detected only in the MS challenged groups. The results demonstrate a possible pathogenesis mechanism of respiratory origin to the layer E. coli peritonitis syndrome, show the MS pathological effect in layers, and suggest that a virulent MS strain can act as a complicating factor in the layer E. coli peritonitis syndrome. MG is the most pathogenic and economically significant mycoplasma pathogen of poultry. It has become increasingly important to differentiate between MG strains and isolates. We designed a specific and sensitive polymerase chain reaction (PCR) for the amplification of the complete MG intergenic spacer region (IGSR) segment. The MG IGSR sequence was found to be highly variable (discrimination (D) index of 0.950) among a variety of MG laboratory strains, vaccine strains, and field isolates. The sequencing of the MG IGSR appears to be a valuable single-locus sequence typing (SLST) tool for MG isolate differentiation in diagnostic cases and epizootiological studies. MG control with live vaccines was demonstrated to efficacious, and the development of live vaccines usually requires the involvement of several vaccine and challenge strains. We developed real-time PCR assays that absolutely differentiated between the five commercial and laboratory vaccine strains: F, ts-11, 6/85, K5831, K5054, and the common challenge strain Rlow. The assay was also tested in vivo and successfully differentiated between the vaccine and the challenge strains in a quantitative manner.