True about mycobacterium other than tuberculosis:
Correct Answer: Causes decreased efficacy of BCG due to cross immunity
Description: Causes decreased efficacy of BCG due to cross immunity Mycobacteria other than tubercle bacille (MOTT) which occassionally cause human disease resembling tuberculosis have been called atypical 'anonymous' or 'unclassified' mycobacteria. They are also called "environmental" or oppourustics as their natural habitat appears to be soil and water and they cause oppounistic infections in human beings. The name "non tuberculous mycobacteria" (NTM) has gained wide acceptance in recent years. They have also been called paratubercle' , "tuberculoid" and MOTT (mycobacteria other than tubercle bacilli) They are usually referred as MOTT and environmental bacteria in text. Epidemiology MOTT are widely distributed in the environment and are paicularly abundant in wet soil, marshland, streams, rivers and estuaries. Human beings are therefore regularly exposed to mycobacteria as a result of drinking, washing, showering and inhalation of natural aerosols. Such repeated subclinical infection may induce sensitization to tuberculin and other mycobacterial skin testing reagents. There is also evidence that contact with MOTT or the environmental bacteria profoundly affects the subsequent ability of BCG vaccine to induce protective immunity, thereby explaining the great regional difference in the efficacy of this vaccine. They are uncommon in regions where T.B. is endemic while they are common where T.B. is rare. Pathogenesis Compared with Tubercle bacilli, MOTT are of low virulence and although man is frequently infected, ove disease is very uncommon except in those who are profoundly immunosuppressed. Person to person infection does not seem to occur. Four main types of oppounist mycobacterial disease has been described in man Localized lymphadenitis. Skin lesions .following inoculation of bacteria. Tuberculosis like pulmonary lesions Disseminated disease Disseminated disease is seen only in severly immunoconzpromised cases such as H.LV. and in some cases of renal transplant.
Category:
Microbiology
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