Mycoplasmas

BACTERIA

Overview

• Pathogens belong to the Mycoplasma and Ureaplasma genera
• Cause many diseases including contagious bovine pleuropneumonia
• Non-pathogenic mycoplasmas present in the rumen
• Live on mucous membranes of oronasal cavity, conjunctiva and intestines
• 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
• Ureaplasmas produce urease, whereas Mycoplasmas do not metabolise urea
• Serolgy is required for specific identification
• Growth inhibition tests using specific antisera can be used as well as fluorescent antibody tests

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

=

• Cause peritonitis in sheep and peritonitis in goats and peritonitis in pigs
• Can be secondary to IBR
• Enzootic pneumonia of pigs caused by M. hyopneumoniae and M. hyorhinis
• Contagious bovine pleuropneumonia caused by M. mycoides
• M. bovis, M. dispar and Ureaplasma in Enzootic pneumonia of calves
• May cause lymphocytic chronic inflammation (peribronchiolar and perialveolar cuffing).
• M. felis in mild respiratory infection
• M. ovipneumoniae in enzootic pneumonia of lambs
• M. hyosynovia and M. hyorhinis produce syndrome similar to Glasser's disease with milder expression, menigitis rare, arthritis most consistent
• In cattle arthritis