Mycoplasmas

Mycoplasmas are the smallest self-replicating prokaryotes. They are devoid of cell walls, with the plasticity of their outer membrane favouring pleomorphism, although some have a characteristic flask-shaped appearance. Mycoplasmas recovered from humans belong to the genera Mycoplasma (14 species and one candidatus species) and Ureaplasma (two species). They are predominantly found in the respiratory and genital tracts, but sometimes invade the bloodstream and thus gain access to joints and other organs. Diagnosis is made by nucleic acid amplification tests and/or serology. Culture is slow and of limited value in clinical diagnosis. Apart from supportive care, treatment is usually with tetracyclines or macrolides, although an increasing prevalence of macrolide resistance is seen, primarily in Asia. There is no commercially available effective vaccine.