Hello, and thanks for the question.
Here is some information about MAC to get you started: https://www.lung.org/lung-health-diseases/lung-disease-lookup/mac-lung-disease

As for the second part, mycobacteria are everywhere - in air, water and soil. Those of us with underlying lung conditions are more prone to infection from it, but nearly never know where we "caught" it. Proper cleaning of nebulizers and inhalers is important to prevent any infection from getting a head start in your already compromised lungs though. Here is what the Americal Lung Association recommends for cleaning your nebulizer :https://www.lung.org/lung-health-diseases/lung-disease-lookup/copd/patient-resources-and-videos/how-to-clean-a-nebulizer If you also use a vibratory airway clearance device, follow these instructions or the ones you received with it.

Happy to answer any more questions you may have!
Sue