Isolation of Mycoplasma meleagridis from chickens.

Mycoplasma meleagridis (MM) is a major cause of disease and economic loss in turkeys. Formerly it was thought that this species was very host specific and only restricted to turkey. In this study, we report on the recovery of MM from breeding flocks of chickens located near a turkey breeding unit. Ten MM field strains were isolated (by culture on Frey broth medium) from tracheal swabs of chickens displaying clinical signs of mycoplasmosis-essentially respiratory symptoms and poor performance. Assignment of the isolated field strains to MM was confirmed by a growth inhibition assay using MM-specific polyclonal antiserum and by PCR amplification targeting the 16S rRNA sequence as well as the Mm14 sequence, a MM-species-specific DNA fragment previously identified and characterized in our laboratory. The nucleotide sequence of Mm14 proved to be highly conserved among the 10 MM field strains, indicating a common source of infection. However, on the basis of slight differences in sodium dodecyl sulfate-polyacrylamide gel electrophoresis whole-cell proteins and western blot profiles, two groups of the isolated MM field strains could be distinguished. Evidence of MM infection of chickens was further provided by serology, since 13.77% (35/254) of sera proved positive to MM by either rapid serum agglutination or recombinant antigen-based enzyme-linked immunosorbent assay. In addition, sera of all chickens from which MM was isolated were positive for antibodies to MM. Collectively, the data unambiguously show that MM could infect chickens; thus, MM warrants further exploration to determine its pathogenicity in this unusual host.

A recombinant antigen-based ELISA for the simultaneous differential serodiagnosis of Mycoplasma gallisepticum, Mycoplasma synoviae, and Mycoplasma meleagridis infections.

We have previously identified species-specific DNA fragments, referred to as MS2/28 and Mm14, of Mycoplasma synoviae and Mycoplasma meleagridis, respectively. In the present study, we extended our analysis of the MS2/28 fragment that was found to encode a species-specific antigenic site, and we demonstrated the specificity of the Mycoplasma gallisepticum hemagglutinin protein encoded by pMGA1.2 (a member of the vlhA gene family). Then, we combined the Escherichia coli-expressed products of MS2/28, Mm14, and pMGA1.2, to develop a recombinant antigen-based enzyme-linked immunosorbent assay (recELISA), for the simultaneous and specific detection of antibodies to the three aforementioned major avian mycoplasma species. For comparative purposes, a novel in-house crude antigen capture ELISA (capELISA) was developed in parallel. In the latter protocol, the microtiter wells were enriched in species-specific antigens by capturing sonicated crude antigens on coated rabbit polyclonal antibodies that had been extensively adsorbed with the whole antigen of the heterologous species. With regard to rapid serum agglutination, both ELISA tests were highly specific, and they showed a significant correlation when field sera from naturally infected birds were tested. recELISA proved to be highly specific because absorbance values, with the heterologous species, were significantly lower (P < 0.001) than those obtained with capELISA. Given its cost-effectiveness and simplicity, the recombinant antigen-based ELISA seems to represent a valid tool for the specific screening of the three major avian mycoplasma species. recELISA will be particularly useful with regard to trade control because a large number of samples from various fields could be rapidly processed.

Molecular cloning of a Mycoplasma meleagridis-specific antigenic domain endowed with a serodiagnostic potential.

A recombinant phage library harbouring Mycoplasma meleagridis (MM) genomic DNA fragments was generated in the bacteriophage lambda gt11 expression vector. The library was screened for expression of MM specific antigens with a polyclonal antiserum that had been preadsorbed with antigens of the most common unrelated avian mycoplasma species. A 49-amino acid antigenic domain unique to MM was isolated, expressed in Escherichia coli, and its serodiagnostic potential was demonstrated. An antiserum raised against this MM-specific antigenic domain recognized a cluster of seven membrane-associated MM proteins with molecular masses ranging from 34 to 75 kDa. Overall, this study resulted in the identification of a potent serodiagnostic tool and revealed the complex antigenic nature of MM.