What makes mycobacterium resistant to gram staining?
-glycolipids in cell wall
What do glycolipids in the cell wall of mycobacterium do?
-protects bacteria from effects of phagolysosomal components -enhance antibody responses to protein Ags
What organism causes leprosy?
In what populations and areas do most cases of leprosy occur in the U.S.?
-Majority of cases in Asian & Hispanic immigrants; -Most cases occur in New York, Texas, Louisiana & California.
How is Mycobacterium leprae cultivated?
-cannot be cultivated in vitro -must inject into mouse foot
What might be the reservoir of M. leprae?
Distinguish the severity and characteristics of Lepromatous Leprosy and Tuberculoid Leprosy.
Lepromatous Leprosy: -most severe -multiple skin lesions, intact sensation -Few T cells, no granulomas -Lots of bacteria in skin Tuberculoid Leprosy: -Least severe -Few, raised skin lesions -Abundant T cells, well formed granulomas -Almost no bacteria in lesions
How does M. leprae result in nerve damage?
-direct bonding of organisms to schwann cells -immunologic damage to infected nerve cells
How is leprosy related to diabetes?
-both involve loss of sensation in extremities in a glove and stocking distribution -inability to feel leads to repetitive trauma and 2' infections, leading to resorption
What stain is used on the skin to detect leprosy?
Fite stain (acid fast)
What is the treatment of leprosy?
-prolonged therapy with dapsone & rifampin
What is a reversal reaction in leprosy?
-Immunologic reaction that complicates diease -result from development of a more appropriate Th1 cellular immune response; -Increased erythema of skin plaques & swelling of peripheral nerves.
What is erythema nodosum leprosum
-Immunologic reaction that complicates diease -Panniculitis, arthralgias/arthritis, mouth ulcers, fever, proteinuria
What syndromes are caused by Mycobacterium avium-intracellulare(Mycobacterium avium complex)?
Chronic pulmonary disease: -Fibrocavitary -Fibronodular -Disseminated disease in people with AIDS; -Miscellaneous, mostly localized soft tissue infections.
Who is usually infected with Mycobacterium avium-intracellulare, causing Fibrocavitary disease?
-elderly men who are smokers and have COPD
Why is fibrocavitary disease caused by Mycobacterium avium-intracellulare very refractory?
anatomic abnormalities & development of drug resistance.
Who is usually infected with Mycobacterium avium-intracellulare, causing Fibronodular bronchiectasis?
-non-smoking women without predisposing lung disease -Characteristic asthenic (thin) body habitus with scoliosis, pectus excavatum, mitral valve prolapse
Which responds better to therapy, fibronodular bronchiectasis or fibrocvavitary disease? What organism causes it?
-Fibronodular bronchiectasis -Mycobacterium avium-intracellulare
What are the 6 major clinical syndromes caused by nontuberculous mycobacteria?
-Chronic pulmonary disease -Lymphadenitis -Localized cutaneous & soft tissue infections -Infection of tendon sheaths, bones, bursae & joints with all species -Disseminated disease -Catheter-related infections in patients with long-term indwelling intravascular catheters
What is lymphadenitis? What organisms cause it?
-Tends to be painless, anterior cervical adenopathy; -80% in children is MAC; remainder is M. scrofulaceum -TB as well
“swimming pool” or “fish tank” granuloma
What is the presentation of Mycobacterium marinum infection?
Violet papules on hands & arms that progress to ulcerations.
_____________ was implicated in an outbreak of soft tissue abscesses associated with nail salons
"Rice Bodies" in tendon sheaths, bones, bursa, and joints
-All species of non-TB mycobacteria -frequently M. avium-intracellulare
Where is Nocardia normally found?
What does Nocardia brasiliensis cause?
-lymphocutaneous infection, abscess or cellulitis & mycetomas *results from traumatic inoculation
When you see a pulmonary-CNS syndrome in an immunocompromised patient, what organism should you be thinking?
Growth of Nocordia is _______than most conventional bacteria, & other organisms can overgrow colonies of Nocardia unless plates are carefully inspected
A patient with HIV infection (CD4 = 23 cells/ L) presented to the Thomas Street Clinic with weight loss, low grade fevers, Hgb=7.2 mg/dL, enlarged liver & alkaline phosphatase = 584 IU/dL. Chest radiograph is clear. He most likely has: a. Disseminated Mycobacterium marinum b. Disseminated Brucella melitensis c. Disseminated Nocardia brasiliensis d. Disseminated Mycobacterium avium-intracellulare
d. Disseminated Mycobacterium avium-intracellulare
You were consulted by a hand surgeon who biopsied one of the lesions depicted below. The patient had been treated with clindamycin without response. The culture from the biopsy is now growing Mycobacterium marinum. You should ask the patient about: A. An injury related to a salt water aquarium. B. If his occupation is a custodian. C. Exposure to hot springs. D. Both a & c.
D. Both a & c.