mycobacterial infections

Question 1

describe some general characteristics of Mycobacteria

Answer 1

• Lipid-rich cell walls (mycolic acid)
  
  • Gram-stain poorly or not at all
• ACID-FAST STAINING
• Can replicate in macrophages
• GENERALLY SLOW-GROWING (DORMANCY WITHIN GRANULOMAS

Question 2

What are some factors the increase risk of infection of TV

Answer 2

• HIV
• Homeless shelters

Question 3

describe the clincial aspects of M. Tuberculosis (TB)

Answer 3

• Transmission through respiratory droplets
• Primary disease of pulmonary
• May become disseminated, particularly in IMMUNOSUPPRESSED Pts
• Most pts have latent infections (90%

Question 4

Symptoms of Active TB

Answer 4

• General malaise
• fatigue
• fever
• chills
• night sweats
• wasting
• pulmonary insufficiency
• cough
• bloody sputum

Question 5

Latent TV infection VS TB DISEASE

Answer 5

LATENT VS ACTIVE

Chest X ray: NORMAL Vs ABNORMAL

Sputum Smear/culture: NEGATIVE Vs POSITIVE

Symptoms: NONE vs Cough, Fever, Weight loss

NO INFECTIOUS vs OFten infectious before tx

Not a case of TB vs A case of TB

**BOTH are positive for TST or Blood test**

Question 6

what are the obstacles to TB treatement

Answer 6

• Organism is slow growing
• Remains viable but dormant (slow metabolism)
• Rapid development of resistance
• toxicity of treatment = non=compliance

Question 7

what are some solutions to obstancles of TB Treatment

Answer 7

• Regimens must contain multipe drugs to which the organism is susceptible (COMBINATION THERAPY***)
• drugs must be taken regularly
• drug therapy must continue for sufficient time (Direct observed therapy)

Question 8

M. Avium Complex (MAC)

Answer 8

• Can cause pulmonary disease in immuno-competent individuals, and disseminated disease in AIDS patients
• Acquired thorugh:

–> ingestion of contaminated food and water

–> acquired through respiratory droplets

Question 9

What is the preferred Regimen for ACTIVE TB

Answer 9

• Initial phase: Daily Isoniazid, Rifampin, Pyrazinamide and Eethambutol
• Continuation phase: Daily Isoniazid and Rifampin

Question 10

describe recommended regimens for tx of LATENT TB

Answer 10

• Isoniazid –> 6-9 months

OR

• Isoniazid and rifapentine –> 3 months

OR

• Rifampin –> 4 months

Question 11

M. avium COMPLEX (MAC) Treatment

Answer 11

• Combination therapy for MAC pulmonary infections
  
  • Macrolide antibiotic (clarithromycin or azithromycin)
    
    • protein syntheiss inhibitors
  • Rifampin
  • Ethambutol
  • +/- streptomycin
• MAC DISSEMINATED DISEASE
  
  • Macrolide + rifampin + ethambutol
• Prophylaxis in HIV patients = CLARITHROMYCIN or AZITHROMYCIN

Question 12

Describe M. Leprae (leprosy) characteristics

Answer 12

• Two forms
  
  • Lepromatous form
    
    • difiguring skin lesions (nodules and plaques)
    • absence/poor cell mediated immune response
  • Tuberculoid form (milder)
    
    • hypopigmented plaques or macules
    • strong cell mediated immune response

Question 13

describe tx regimen for leprosy

Answer 13

• MULTIDRUG REGIMEN = Dapsone, clofazimine and rifampin
• therapy lasts for years

–> Tuberculoid = 1-2 yrs

–> lepromatous = 5 years