Category:Mycoplasmas


Overview

  • Pathogens belong to the Mycoplasma and Ureaplasma genera
  • Cause many diseases especially respiratory diseases of farm animals including contagious bovine pleuropneumonia
  • Can be involved in mastitis and conjunctivitis in cattle
  • Implicated in respiratory and urinary tract diseases in dogs and cats
  • Non-pathogenic mycoplasmas present in the rumen
  • Live on mucous membranes of oronasal cavity, conjunctiva and intestines
  • Stress factors and concurrent disease may predispose to tissue invasion
  • Usually host-specific
  • Limited survival in the environment


Characteristics

  • Smallest free-living prokaryotic organism
  • Pleomorphic organisms
  • Have no peptidoglycan cell wall
  • Susceptible to dessication, heat and disinfectants
  • Require enriched media containing animal protein, sterol and a source of DNA for growth
  • Colonies have a fried egg appearance
  • Most are facultative anaerobes


Pathogenesis and pathogenicity

  • Mycoplasmas adhere to host cells and produce toxins
  • Some adhere to neutrophils and macrophages and prevent phagocytosis
  • Mycoplasmas induce proliferation of macrophages and [[monocytes]], and release of cytokines such as TNF and interleukins
  • Cause damage to cilia in the respiratory tract leading to pneumonia
  • Molecular mimicry allows some mycoplasmas to avoid the host immune response and may initiate immune-mediated disease


Diagnosis

  • Samples can be tested for the presence of mycoplasmas by fluorescent antibody techniques, peroxidase techniques and PCR
  • Biochemical profiles such as urease production can be used for identification
  • Ureaplasmas produce urease, whereas Mycoplasmas do not metabolise urea
  • Serolgy is required for specific identification including complement fixation tests, ELISA, agglutination tests and haemagglutination-inhibition tests
  • Growth inhibition tests using specific antisera can be used as well as fluorescent antibody tests


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Other mycoplasmas