EXAM #2: MYCOBATERIA INFECTIONS Flashcards
Where are nontuberculous mycobacteria found? How are they transmitted?
NTM are found ubiquitously in soil and water; they are transmitted via inhalation
List the nontuberculous mycobacteria.
Mycobacterium avium complex (MAC)
Mycobacterium kansasii
Mycobacterium marinum
Mycobacterium scrofulaceum
What does MAC infection refer to?
Infection caused by:
1) Mycobacterium avium
2) Mycobacterium intracellulare
What specific patient population is at risk for MAC infection?
HIV patients with CD4 count less than 50
How is MAC infection differentiated from TB?
MAC is distinguished from TB by the presence of:
1) Anemia
2) Elevated alkaline phosphatase
3) Elevated lactate dehydrogenase
What is the regimen for MAC prophylaxis? When is this started? What about MAC treatment?
Prophylaxis= CD4 count less than 50
- Azithromycin or clarithromycin (macrolides)
Treatment
- Azithromycin or clarithromycin (macrolides) + ethambutol
What clinical symptoms are caused by M. kansasii transmitted? How is it transmitted?
- M. kansasii causes sx. indistinguishable from TB
- Transmitted via tap water in affected cities (Kansas)
*Note that CXR will be like typical TB with cavitation
What is the clinical presentation of M. marinum? Where is it commonly found?
- M. marinum causes papules or ulcers in a lymphocutaneous pattern
- Water sources associated with aquarium cleaners, fisherman, and seafood handlers
What is the mnemonic to remember the agents commonly used to treat NTM?
MARIE
- Macrolides
- Aminoglycosides
- Rifamycins
- Isoniazid
- Ethambutol
Worldwide, what are the two most common causes of death from an infectious disease?
1) HIV
2) TB
What caused the increased TB prevalence that started in 1985-1986?
HIV epidemic
What are the high risk setting for acquiring TB? Geographically, where are the highest rates of TB infection?
High risk=
1) Prisons
2) Hospital
3) Homeless shelters
Geographically=
1) Sub-Saharan Africa
2) India
3) Southeast Asia/ Indonesia
How is TB transmitted?
Inhalation of droplet nuclei i.e. airborne particles
What are the three possible consequences of inhaling TB droplet nuclei?
1) Clearance w/out infection
2) Primary TB
3) Secondary TB
What is Primary TB?
TB infection arising from initial infection/ early progression
What is Secondary TB?
Reactivation of latent/contained TB
- Primary infection years prior gets contained by immune system
- Altered immune system–> development of symtoms
How is Primary TB described on CXR?
“Ghon Complex”
- Spread of TB to lymphatics
- Regional lymphadenopathy= complex
If symptomatic, what clinical symptoms are associated with primary TB?
1) Fever
2) Chest pain with pleural effusion
What is the typical disease course of primary TB?
1) 90% become asymptomatic–infection contained but not eradicated (latent TB)
2) 10% progress to develop infection
How is latent TB diagnosed?
1) Positive TB skin test
- “Mantoux technique”
2) Interferon gamma release assay (IGRA)
Note that steroid use, malnutrition, and an immunocompromised state can lead to a false negative test
How are the results of a PPD skin test documented?
mm of INDURATION (thickening of the skin) not erythema
This will be a test question
If a patient has a positive TB skin test IGRA, what does this mean?
LATENT TB infection, NOT active disease
What is the important distinction between the PPD skin test and IGRA with regards to the BCG vaccine?
IGRA will NOT be affected by the IGRA
*PPD will be positive if the patient has had BCG vaccine
What should you do if a patient has a positive PPD skin test?
1) Measure induration
2) Risk stratify to determine if test is positive
What is indicated when a patient has a positive PPD test?
Prophylactic therapy w/ Isoniazid 300mg x 9 months
*Plus pyridoxine (B6)
What medical conditions are considered high risk for TB?
1) Silicosis
2) DM
3) Chronic renal failure
4) Gastrectomy/ jejunoileal bypass
5) Weight loss
6) Children under 4 y/o
What are the classic symptoms of active TB?
1) Cough
2) Fever
3) Night sweats/chills
3) Hemoptysis
4) Weight loss
What are the general principles of TB therapy?
1) At least 2x drugs
2) Always use appropriate doses
3) Drug must be taken regularly
4) Long duration therapy
What drugs are used for the induction phase of TB treatment? How long is this phase of treatment?
RIPE
R= Rifampin I= Isoniazid P= Pyrazinamide E= Ethambutol
*First 2x months of therapy
If the patient has negative sputum cultures and a negative CXR after the first two months of treatment, what do you do?
Stop Pyrazinamide and Ethambutol
What drugs are used for the continuation phase of treatment in TB? How long is this phase of treatment?
1) INH
2) Rifampin
4-7 months
What do you do in a patient that is sputum positive and/or has a positive CXR after the first two months of therapy?
1) Continuation of induction therapy
2) Consider drug resistance
What is the definition of Multidrug Resistant TB (MDR-TB)?
Lab confirmed resistance to INH and RIF
What is diagnostic for active TB?
Positive sputum culture
What is scrofula?
Mycobacterial cervical lymphadenitis
*This is a lymphadenitis of the cervical lymph nodes that usually appears as a chronic painless mass in the neck
What is Pott’s Disease?
Skeletal infection with M. tuberculosis, esp. involving the spine
What is a Ranke complex?
Ghon complex that has undergone fibrosis and calcification
What stain is used to diagnose tuberulous meningitis? Where is this normally located?
Ziehl-Neelsen stain
*Granulomas are found at the base of the skull
What is the most common organ to be involved with systemic spread of TB? What is the result?
Kidney, resulting in sterile pyuria
