Final answer:
Mycobacterium tuberculosis is the acid-fast positive bacterium in the provided samples due to its mycolic acid-rich cell walls, which retain the red color from the primarily used carbol fuchsin stain in the acid-fast staining protocol.
Step-by-step explanation:
Identifying Acid-Fast Positive Bacteria
The only acid-fast positive bacteria mentioned is Mycobacterium tuberculosis, which is characterized by its resistance to decolorization and its ability to retain the primary stain when subjected to the acid-fast staining protocol. This staining technique involves using carbol fuchsin as the primary stain, heating the slide to allow dye absorption, decolorizing with acid and alcohol, and counterstaining with methylene blue. Since M. tuberculosis contains high levels of mycolic acid in its cell walls, it retains the red color of the carbolfuschin after the decolorization step, differentiating this species from non acid-fast bacteria.
According to the lab results provided, the presence of colorless granulated colonies which were identified to be AFB through nucleic acid hybridization supports the identification of M. tuberculosis as the acid-fast positive bacterium from the samples. The lab also observed the similar microscopic characteristics these colonies shared with those present in Marsha's sputum, which along with additional DNA evidence confirmed Marsha's diagnosis and successful treatment for tuberculosis after nine months. Thus, amongst the bacterial samples in the lab, M. tuberculosis is the acid-fast positive bacteria.