Due to media requirements and the slow growth of Mycoplasma, the cultivation of the agent is sometimes difficult and always time consuming. Often cross-reactions appear by using the immunofluorescence test as well as serological detection techniques, which can influence specificity negative.
These cross-reactions are likely to appear because of the close relationship of MmmSC to a number of other Mycoplasma species. Mycoplasma species listed below belong to the so called Mycoplasma-mycoides-cluster, that shares a number of common antigens and therefore makes it sometimes impossible to distinguish them with traditional detection methods.
Important Mycoplasma species for differential diagnostics are
- M. mycoides subsp. capri
- M. capricolum subsp. capricolum
- M. capricolum subsp. capripneumoniae
- M. leachii
The diagnosis of CBPP often relies only on the complement fixation test (CFT), which is recommended by the Office International des Epizooties (OIE). Yet this serological method is known for its low sensitivity and problems with specificity. In the past there have been cases reported where cattle were tested positive by CFT in Germany. That these positive reactions are caused by cross-reactions could be shown only by immunoblotting, another serological method recommended by OIE, which is characterized by a much higher specificity and sensitivity.
Immunoblotting uses separation by electrophoresis of the MmmSC antigen followed by immobilization of the separated proteins on a membrane. This antigen-covered membrane will then be incubated with the sera to be investigated including control sera. Reactive bands are made visible by a change of color due to an enzymatic reaction. A sample is proven positive, if certain bands with a defined molecular weight (110, 98, 95, 62/60, and 48 kDa) can be detected. With this method a more precise result regarding the presence of antibodies against MmmLC is possible and so immunoblotting is recommended in cases of unclear CFT results.
Another alternative method recommended by the OIE, besides CFT, is a commercial antibody ELISA (CIRAD, France), but this test is not licensed in Germany and can therefore only be used with special permission.