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Question: colonization and/or infection w/MAC

Posted by lvnl @lvnl, Aug 17 2:54pm

Question for @sueinmn and anyone who is generous with solid knowledge from researching this pesky condition. I have mild bronchiectasis found in 2010, & positive for MAC as of this past spring. I didn't have symptoms & CTs/PFTs have been stable until I developed chronic dry cough 1-2 yrs ago which eventually showed MAC-positive sputum cultures. I am not ill, no fever, but very fatigued. Now in screening phase for Encore Arikayce study; either way I will be treated with antibiotics since I'm on Humira (for Crohns) which no one wants to stop. This question is more curiosity about how MAC "works" since at this point I am confident in my treatment:
"Colonization" means you have cultured positive for MAC in your lungs but may not be ill. But MAC is everywhere -- is it found in "healthy" people's lungs also but to no effect? [For example: many if not most people "have" e-coli in their bodies and there are many kinds of e-coli, but most people do not get ill from it.] Are most people essentially "colonized" with MAC? Or, does a "healthy" person's immune system keep MAC from taking up residence in their lungs or showing up in sputum?
Thank you for any insight to satisfy this curiosity and best wishes to all in understanding and treating!

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Mentor
Sue, Volunteer Mentor | @sueinmn | Aug 18 10:55am

@lvnl I have read a lot, but am by no means an expert in this infection.
What I can tell you is that if someone has their sputum tested using an AFB test, where a stain is applied to the slide, if "AFB bacteria" appear they follow with a culture of the specimen. The specimen MAY grow a mycobacteria - TB, MAC, M Abscessus, or another NTM.
My husband had AFB specimens show bacteria, but the culture is negative. This means it may have been in his sinuses, mouth, throat or even lungs but was not present in his lungs in sufficient quantity to grow.
When you are described as "colonized" it means that the bacteria is there, but you don't meet the criteria of having an active infection.
Active infection requires 3 components as outlined in this article:
https://www.cdc.gov/nontuberculous-mycobacteria/hcp/clinical-overview/index.html
Sorry I cannot directly answer your question - I'm not sure anyone has performed sputum testing on asymptomatic people - I'm not even sure how they would provide a sputum specimen without a bronchoscopy. But it seems unlikely that MAC or any of the other infections that visit us are able to colonize healthy lungs in healthy people.

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lvnl | @lvnl | Aug 19 4:13pm

Thank you @sueinmn for taking time to respond. So much about bronchiectasis and MAC is still being learned.

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lvnl | @lvnl | Aug 19 4:34pm

I found this very long article on the state of research into the lung microbiome that as much as I can understand it (which is not much!) indicates that study of the lung microbiome & its relation to immunity is in its infancy compared to understanding of gut microbiome for ex. There is a short section on bronchiectasis.
https://www.nature.com/articles/s41392-023-01722-y

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Mentor
Sue, Volunteer Mentor | @sueinmn | Aug 19 6:00pm
In reply to @lvnl "I found this very long article on the state of research into the lung microbiome that..." + (show)
@lvnl

I found this very long article on the state of research into the lung microbiome that as much as I can understand it (which is not much!) indicates that study of the lung microbiome & its relation to immunity is in its infancy compared to understanding of gut microbiome for ex. There is a short section on bronchiectasis.
https://www.nature.com/articles/s41392-023-01722-y

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Thanks, this is a fascinating article. I think the takeaway is that bacterial colonization doesn't occur in healthy lungs.

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reneemc | @reneemc | Aug 20 9:58am

What is the encore Arikayce study?

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