In water damaged indoor environments other "pathogens" (disease causing to humans) besides fungus exist. Mycobacterium is one of them. Mycobacteria can colonize in their hosts without the hosts showing any adverse symptoms or health signs. For example, billions of people around the world have asymptomatic infections of M. tuberculosis.

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae). The Greek prefix "myco" means fungus, alluding to the way mycobacteria have been observed to grow in a mold-like fashion on the surface of liquids when cultured. 

Mycobacterial infections are notoriously difficult to treat. The organisms are hardy due to their cell wall, which is neither truly Gram negative nor positive. In addition, they are naturally resistant to a number of antibiotics that disrupt cell-wall biosynthesis, such as penicillin. Due to their unique cell wall, they can survive long exposure to acids, alkalis, detergents, oxidative bursts, lysis by complement, and many antibiotics.

This is why having a knowledgeable and experienced physician familiar in all aspects of environmental health and those components synergistic with fungal growth is a must for proper treatment for mold exposure and mold sickness.