Difference between revisions of "Category:Mycobacterium species"

Overview

• Mycobacterial infections are caused by bacteria belonging to the family Mycobacteriaceae, order Actinomycetales
• Includes obligate pathogens, opportunistic pathogens and saprophytes
• Cause chronic, progressive, granulomatous infections
• Cause tuberculosis, Johne's disease and feline leprosy
• M. bovis, M. tuberculosis and M. avium cause tuberculosis of cattle, tuberculosis of pigs and tuberculosis of dogs respectively
• The 'classical' tuberculosis lesions are caused by the Mycobacterium tuberculosis complex
• The Johne's type lesions are caused by the Mycobacterium avium complex
• Environmental species are found in soil, vegetation and water
• Mycobacterium leprae and M.lepraemurium cause human, feline/murine leprosy respectively
• Atypical mycobacteriosis is a localized opportunistic skin and subcutaneous infection caused by saprophytic and rapidly growing atypical mycobacteria
• Granulomatous lesions in muscle and skin
• Skin tuberculosis of cattle causes nodules along the lymphatics of the limbs
• Bovine farcy is thought to be caused by M. senegalense and M. farcinogenes
• Saprophytic mycobacteria cause granulomatous lesions

Characteristics

• Aerobic, weakly Gram-positive acid-fast rods
• Non-motile, non-spore forming
• Cell walls contain mycolic acid
• Require egg-based media for growth
• Slow-growing colonies
• Resistant to disinfectants and environmental conditions; susceptible to pasteurisation
• Mycobacteria stain with carbol dyes and resist subsequent decolorization with inorganic acids; this characteristic which is due to the spatial arrangement of mycolic acids within the cell wall makes them acid fast

Identification

• Identified by Ziehl-Neelson staining
• Differentiated by culture, biochemical tests, chromatography and molecular techniques
• Pathogenic species require at least three weeks for growth on egg-based media