If the culture plate is positive, a colony count can be done - it is just that not every lab has it in their standard protocol, it needs to be requested in the doctor's order. And labs do it different ways - some quantify it as none, few, many, etc. Others apply an algorithm of some sort and arrives at a ##/ml of the culture.

The specimen from a bronchoscopy itself is a little different because a wash is usually a larger quantity, but more diluted by the saline used to get it. However the testing process is the same. But these are used in the same way to get an exact diagnosis.

A slide is used first, with a small amount of the specimen, to ID rapidly growing bugs, and "gram positive rods" (also referred to as AFB positive) or similar terminology. Perhaps washes are more likely to produce a negative slide because it is more diluted, or it may be because the infection is very limited (mild.)

The culture is performed by placing more of the specimen onto a culture plate, which is the incubated at a specific temperature for up to 8 weeks. This is where the NTM (non-tubercular mycobacteria) either grows or does not. After a few weeks of growing, if it shows up, it is analyzed to see which mycobacteria it contains.

Many mycobacteria may be there, but some are not harmful to us, so are not treated. Others are slow growing, and may or may not be treated, based on how many there are, and how many symptoms the person has. Other efforts to A few (most often m. abscessus) are treated as soon as identified, because they can grow more aggressively.

This is a crazy, complex system for finding the best approach for each person. Please know that the statistics show that as many as 50% of the people have a positive culture the first time get a negative one the next time. We don't really know why. Also, as a person who knows you are infected to some degree, there are things you can do to keep the infection down, even possibly get rid of it, without antibiotics.

Have your doctors talked to you about using 7% saline and airway clearance?
Sue