Mycoplasmas, the smallest free-living organisms known, are prokaryotes that are bounded only by a plasma membrane. Their lack of a cell wall is associated with cellular pleomorphism and resistance to cell wall-active antimicrobial agents such as penicillins and cephalosporins. The organisms’ small genomes limit biosynthesis and explain the difficulties encountered with in vitro cultivation. Mycoplasmas typically colonize mucosal surfaces of the respiratory and urogenital tracts of many animal species. Sixteen species of mycoplasmas have been recovered from humans. M. pneumoniae causes upper and lower respiratory infections. M. genitalium and Ureaplasma urealyticum are established causes of urethritis and have been implicated in other genital conditions (Haggerty et al., 2008).

Mycoplasmas are well known as the pathogens of mycoplasma pneumonia, and have also come to be recognized as causative bacterias in asthma, rheumatic diseases and neurological disorders (Waites et al., 2004; Atkinson et al., 2009; Gil et al., 2009; Kawahito et al., 2008). Also it is suspected that mycoplasmas are related to atherosclerosis and tumours (including leukaemia) (Alviar et al., 2011; Nussinovitch et al., 2010). The concept of mycoplasma-caused infectious diseases has changed to include not only pneumonia but also other serious illness, now termed mycoplasma-related disorders.

Since drug-resistant mycoplasmas have already appeared, early diagnosis and therapy of infectious diseases caused by mycoplasmas have become more important. However, there are no reliable diagnostic methods for early diagnosis of mycoplasma infections currently in clinical use. A major reason for this lack of a diagnostic method is that antigens used for conventional diagnostic methods are derived from partially purified extracts from mass cultured mycoplasmas or from recombinant proteins.