Non tuberculous mycobacterium Notes

NOTES NOTES NON TUBERCULOUS MYCOBACTERIUM MICROBE OVERVIEW ▪ Pleomorphic acid-fast bacillus; usually rodshaped ▪ Thick waxy coating ▪ Obligate intracellular microorganism ▪ Optimal growing conditions: cool temperatures (27–33ºC/80.6–91.4°F), aerobic environment ▪ Proliferates slowly; cannot be cultivated in vitro ▪ Appearance: red; Ziehl–Neelsen stain MYCOBACTERIUM LEPRAE osms.it/mycobacterium-leprae PATHOLOGY & CAUSES ▪ Primarily infects skin, superficial nerves, upper respiratory tract mucosa, eyes ▪ Chronic infection: leprosy; AKA Hansen’s disease ▪ Targets Schwann cells → nerve damage → sensation loss → repeated injuries, infections → gradual destruction of extremities ▪ Infiltration of skin, cutaneous nerves → hypopigmented skin lesions Ridley-Jopling classification ▪ Tuberculoid ▫ ↑ cell-mediated immunity response ▫ AKA paucibacillary (↓ mycobacteria) ▪ Lepromatous ▫ ↓ cell-mediated immunity response ▫ AKA multibacillary (↑ mycobacteria) ▪ Broad disease spectrum ▫ Borderline tuberculoid, mid-borderline, borderline lepromatous, indeterminate 458 OSMOSIS.ORG RISK FACTORS ▪ Close contact with infected individuals (esp. in areas of poverty), armadillos (enzootic in Dasypus novemcinctus) ▪ Older age, genetic factors, immunosuppression COMPLICATIONS ▪ Lifelong neuropathy → severe disfigurement, disability ▪ Severe ophthalmic injury → vision loss ▪ Social stigma (falsely believed contagious) SIGNS & SYMPTOMS ▪ Can be asymptomatic for years ▪ ↓ sensation ▫ Glove, stocking pattern → repeated painless injuries ▪ Hypopigmented/reddish skin lesions, heal spontaneously ▫ Tuberculoid: rare, well-demarcated ▫ Lepromatous: numerous, poorly demarcated

Chapter 83 Non Tuberculous Mycobacterium Nodular swelling (face, earlobes) Body hair loss (esp. eyebrows, eyelashes) Tender, thickened peripheral nerves Ocular involvement ▫ Chronic uveitis (common) ▫ Facial nerve paralysis (lagophthalmos) → corneal exposure, dry eye → corneal ulceration ▪ Late stages ▫ Claw fingers, toes ▫ Foot droop (inability to lift front of foot); peroneal nerve infiltration ▫ Nasal septum destruction → nose collapse (saddle nose) ▪ ▪ ▪ ▪ Figure 83.1 A skin lesion on the scalp of an individual with leprosy. DIAGNOSIS LAB RESULTS ▪ Skin biopsy of active lesion ▫ Mycobacteria in cutaneous nerve ▪ Polymerase chain reaction (PCR) ▫ M. leprae DNA in tissues OTHER DIAGNOSTICS ▪ Clinical examination Figure 83.2 The hands of an individual with leprosy. The distal portions of almost all the digits, aside from one, have been lost. TREATMENT MEDICATIONS ▪ Multidrug therapy to prevent resistance ▫ Tuberculoid: dapsone, rifampicin; six months ▫ Lepromatous: dapsone, rifampicin, clofazimine; 12 months OTHER INTERVENTIONS Figure 83.3 Skin changes on the chest of an individual infected with Mycobacterium leprae. ▪ Bacillus Calmette–Guérin (BCG) vaccination ▫ Administered at birth in regions with increased leprosy rates (e.g. Brazil, India, Indonesia) OSMOSIS.ORG 459