Mycobacterium
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- How is M. tuberculae visualized? Why is this technique used?
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*Acid-fast staining
*waxy coat prevents Gram staining - What is the O2 preference of M. TB? Does it like to live inside or outside of cells?
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*obligate aerobe
*facultative intracellular pathogen - How is TB transmitted?
- Aerosol - inhalation of droplet nuclei.
- What caused the rise of TB in the early 1980's?
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*HIV/AIDS
*influx of immigrants from endemic areas
*dismantling of public health infrastructure - After the microbe has entered the body, what does M. TB do next?
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*ingested by alveolar macrophages
*prevents phagosome-lysosome fusion in inactivated phages
*IC replication followed by host cell lysis
*may be transported throughout RES - What symptoms are seen in primary TB? What's the course of this condition?
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*flu sx
*cell-mediated immune response results in granuloma (casein) formation
*viable bugs remain in granuloma - How does secondary TB occur? What symptoms are seen?
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*Oranisms inside granuloma are re-activated and spread
*fever, night sweats, wt loss
*tissue damage may result in cavitation - Is infection by TB restricted to the lungs?
- No - M. TB can infect virtually any part of the body.
- What are some ways TB is detected? What are some problems with each?
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*PPD: false+ for BCG recipients, false- for HIV pts
*culture: slow-growing
*sputum smear: poor sample
*Bac-Tec
*CXR: non-specific - How is TB treated? What are some difficulties? What's been done to lessen these?
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*6-8 month course of rifampin, INH, ethambutol
*poor compliance
*DOTS has increased compliance - Is there a vaccine for TB? What are its drawbacks?
- Yes - the BCG vaccine. Efficacy is variable and all recipients will give a false+ PPD.
- What's been the biggest obstacle with the study of M. leprae?
- Unable to culture in vitro - animal models must be used.
- Describe the transmission and incubation of M. leprae.
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*not highly infectious
*transmitted by inhalation
*5-yr incubation period
*lepromatous nodules contain numerous bacteria - What 2 symptoms appear in both forms of disease caused by M. leprae?
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*disfigurement
*dennervation - Where in the body does M. leprae live?
- In macrophages and Schwann cells.
- What are the 2 disease forms caused by M. leprae? What are the characteristics of each?
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1.Tuberculoid: good Th-1 immune response; hypopigmented lesion; neuropathy
2.Lepromatous: poor immune response; large, bacteria-filled nodules on skin - How is infection with M. leprae treated?
- 6-12 month triple antibiotic regimen
- What distinguishes the photochromagens?
- They are slow growing and produce a yellow pigment when grown in the light.
- What class of MOTT is M. kansasii? What type of disease does it cause?
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*photochromagens
*pulmonary disease common among HIV pts in the midwest - What class of MOTT is M. marinum? What kind of disease does it cause?
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*photochromogen
*"swimming pool granuloma"
*chronic draining ulcer
*2-6 week incubation - What distinguishes the scotochromogens? Describe 2 microbes that fall in this class.
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*slow growing
*produce a yellow pigment in lighth or dark
*M. scrofulaceum - lymphadenitis
*M. gordonae - culture contaminant - How might nonchromagens be recognized? Name 2.
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Their slow growth and inability to produce pigment under any conditions.
*M. avium complex, M. paratuberculosis - How is MAC acquired? What patient population does it affect most often? Treatibility?
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*inhalation or ingestion of contaminated water
*causes pulmonary disease in HIV, COPD, and CF pts.
*high multi-rx resistance - With what disease has M. paratuberculosis been linked?
- Crohn's disease.
- The majority of Runyon Class IV MOTT (rapid-growers) are associated with a single disease type. What is this?
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*M. fortuitum, M. chelonei, and M. abscessus are associated with skin abscesses and wound infection
*M. smegmatis is non-pathogenic - What is the only MOTT that doesn't fall under Runyon classification? What does it cause?
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*M. ulcerans
*necrotizing skin ulcer associated with trauma (Buruli ulcer)