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23 Cards in this Set
- Front
- Back
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Aerobic Actinomycetales
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gram positive
aerobes catalase positive colonizes humans and animals can be delicate hyphae or coccobacilli |
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where are aerobic actinomycetales found
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feeding on decaying vegetation
soil water |
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things that have mycolic acid in cell wall
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Acid fast or weakly acid fast
•Mycobacterium •Nocardia •Corynebacterium |
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Most common cause of infection by NTM
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1. MAC - Mycobacterium avium complex***
•M avium & M intracellulare 2. Mycobacterium kansasii |
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DMAC – disseminated MAC
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•Most common cause mycobacterial infection - AIDS
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how do you identify MAC
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•Biochemical tests initially - difficult to differentiate two microbes •Called MAI
•Molecular techniques DNA/RNA probes •Southern and Northern Blots (FYI) |
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Etiology - M. avium & M. intracellulare
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•Both are weakly Gram-Positive aerobic bacilli
•Both are strongly Acid-Fast •Both are ubiquitous |
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Growth of MAC
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•MAC, like MTB, slow growing organism
•10-12 hours doubling time •Colonization not = Disease •Grow optimally at 41 C |
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Virulence factors of MAC
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•MAC, like MTB, - capable of intracellular growth
•Disease - result of host response to infections (MTB) •MAC - intrinsic resistance to disinfection - |
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Epidemiology of MAC
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•Unlike MTB - MAC infection by inhalation OR ingestion •NO - Person to person transmission
•MAC infections worldwide -ubiquitous like microbe |
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what type of people get MAC
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•Both M avium and M intracellulare •Disease in immunocompromised hosts
•Pulmonary MAC - immunocompromised NON HIV+ •Preexisting infection (lung disease) or immunosuppressed |
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how does MAC cause an Initial infection
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•Initial infection = colonization of GI tract or RT
•Invade & translocate mucosal epithelium •Infect resting macrophages/inactivated - lamina propria •Spread to submucosa •Carried to lymphatics and lymph nodes |
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What is the pathology in immunocomprimised hosts for MAC infection
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•Subsequently spread by hematogenous route
•Liver, spleen, bone marrow, etc. |
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forms of presentation of MAC in immunocompetent
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Usually presents 1 of 3 forms
1. Pulmonary MAC 2. Lymphadenitis 3. DMAC |
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describe pulmonary MAC in immunocampetent host
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can be fibronodular disease
can be fibrocavitary disease |
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A. Fibrocavitary Disease
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• Upper lobe disease
• Elderly male smokers • Chronic pulmonary symptoms due to lung disease • Difficult to distinguish form underlying disease • MAC easily removed from sputum |
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. Fibronodular Disease
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• Fastidious, elderly, female nonsmokers
• Age: >50 yr • Lingular or middle lobe infiltrates Patchy nodular – CXR • With bronchiectasis – • Chronically suppress cough-reflex Leads to nonspecific inflammatory changes Predisposes to MAC superinfection • Similar clinical characteristics & body type Scoliosis, pectus excavatum, mitral valve prolapse Underlying CT disease? • Known as Lady Windermere's Disease |
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who does lymphadenitis affect in immunocompetent hosts
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Children – 1-4 years
Primarily involves unilateral cervical nodes |
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who does DMAC affect
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• Most common mycobacterial infection -advanced AIDS
• CD4 50 cells/L and DMAC • Signs and Symptoms • FUO (Fever Unknown Origin) • Sweating; weight loss; fatigue • Diarrhea • Dyspnea • Upper right quadrant pain |
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what is the course of DMAC in immunocompromised hosts
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• Granulomas not effective in containing MAC*
• Disease disseminates hematogenously Any organ – large numbers of bacteria • Infected organs - enlarge and become dysfunctional *IFN-y & TNF-a - important in defense against mycobacterial infections |
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some ways to decrease the sign of DMAC in immunocomprimised
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• Immune reconstitution syndrome (IRS)
• As HAART/HEART progresses • Highly Active/Effective Antiretroviral Therapy Rebound in CD4 levels Sudden increase in inflammatory response Produces nonspecific symptoms |
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are you required to report MAC
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•Not Reportable UNLESS an AIDS Confirming Illness •Unlike MTB
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how do you diagnose MAC
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•Illness consistent with NTM disease
•Exclude - other etiologics (fungi, TB) •(KP) Causative mycobacterium •Isolated and consistent with illness •Sterile site isolation - probably significant - •Repetitive isolation not required •Peripheral blood or other •Blood may contain ~5X102 to ~5X103 CFU/mL •DMAC - high numbers present infected organs •Isolation •Non-sterile Sputum or bronchial wash May represent colonization •Lymph nodes •Low bacterial counts •May require cultivation for confirmation •Identify to species*** •Same techniques MTB •CXR - important diagnostic •Reveal pulmonary lesions •May require CT or HRCT for limited infections |
