MAC Flashcards
MAC is a group of free living
non TB mycobacteria that are ubiquitous to environment seen in aerolized water, piped hot water systemis bathrooms, house dust, soil, birds, and farm animals.
how do people get MAC?
inhalation of aerosolized municipal water but transmission can occur through contaminated soil, food and animals (birds)
who gets worse course with MAC dx?
severe immunodeficiency (AIDS)
chronic pulmonary infections in those with underlying lung dx
non smoking women
>50 years old
does MAC need airborne precautions
no
hot tub lung
hypersensitivity pneumoitis - can be seen in pts with recent exposure to contaminated hot tub water.
acute flu like illness with dypsnea, cough, malaise, fever0
MAC,
treatment of hypersensitivity pneumonitis or hot tub lung
generally self limited infection and resolves with close observation, supportive care and avoidance of hot tub. But if symptoms persist may need short course of steroids
acute flu like illness and severe headaches, dyspnea cough, malaise and recent exposure to birds
see chlamydia psittaci and has severe headaches.
How does pseudomonal infections present
as folliculitis and not pneumonia.
HIV negative MAC can be seen in pts with and without underlying lung disease and this presents as
cough
MAC infections are generally in pts who have underlying lung dx (cystic fibrosis, COPD, alpha 1 antitrypsin def).
Can also happen in people who have prior lung dx (hot tub lung)
what is MAC and MAI?
MAC is mycobacterium avium complex and includes others like M avium and M intracellulare and so they together are term M avium-intracellulare or MAI
diagnosis of MAC
Diagnosis is based on clinical + microbiological evidence
clinical with CXR with nodular or cavitary lesions OR CT with multifocal bronchiectasis and nodules
PLUS
microbiological >2 positive sputum cultures for MAC
1 positive culture from bronchial wash/lavage
lung biopsy with consistent findings and positive culture.
Criteria must also exclude other causes
treatment of MAC or MAI
at least 1 year of combination of 3 drugs:
- macrolide (clarithromycin or azithromycin),
- ethambutol,
- rifamycin (rafampin or rifabutin)
four drug therapy is for
mycobacterium tuberculosis
do we use a tuberculin skin test for diagnosis of MAC?
no it’s only meant for latent myco TB testing and not for MAC testing.
clinical features of MAC infection in those with underlying chronic pulm dx and those without pulm dx
Diagnosis of MAC
Since MAC can contaminate or colonize sputum need to confirm MAC infection with:
2 positive sputum cultures.
If with only one AMC positive sputum culture need another one to establish diagnosis. If repeat sputum culture is negative, need a positive culture from BAL specimen to treat.
CT scan of MAC infecgtions
can have nodular opacities and see bronchiectasis and see it affected in the right middle lobe and left lingula and other structural lung dx.
Only do CT guided biopsy of pulmonary nodule if repeat sputum cultures or BAL are negative for MAC in order to establish diagnosis.
Opportunistic infections in HIV
We no longer provide MAC prophylaxis.
See MAC infections with CD4 <50
features of non HIV MAC based on if there’s presence of underlying lung disease
treatment of HIV and MAC
