Tuberculosis is caused by Mycobacterium tuberculosis (M.TB.), has a unique cell wall, making it difficult to kill and stain. Three matjor components compose the cell wall: mycolic acids, cord factor, and Wax-D. M.TB. is also hard to culture and can only thrive in the body. It is an obligate aerobe and an acid-fast bacteria. Tuberculosis can be diagnosed through the Mantoux test and by staining methods such as the Ziel-Neelsen method. Chest x-rays are also used in the diagnosis process to detect any damage done to the lungs.
Tuberculosis is caused by M.TB. This bacterium is hard to kill because of its cell wall, which is 60% lipid. M.TB. is also difficult to stain and culture (Todar, Kenneth paragraoh 14). Skin tests and microbiologic smears and cultures are the main methods used to diagnose TB, though the full diagnosis consists of many more tests.
M.TB. is a rod-shaped bacterium related to the Actinomycetes. The rods are 2 to 4 um long and 0.2 to 0.5 um wide. This bacterium is an obligate aerobe, an organism that needs oxygen to survive. It is a tough bacterium that can withstand weak disinfectants and can survive in a dry state for weeks. M. TB. is a slow-growing bacterium that divides every 16 to 20 hours, which is extremely slow compared to other bacterium, which have division times measured in minutes (Wikipedia paragraph 1). Although M.TB. contains peptidoglycan in their cell wall, it is neither Gram-positive nor Gram-negative because it lacks the chemical characteristics of either. The Mycobacterium species is classified as acid-fast bacteria because it is virtually impermeable to certain dyes and stains, but once stained, the dye is permanent. The Ziehl-Neelsen method is one method used to stain Mycobacterium tuberculosis. When this stain is used, the bacterium is stained with carbol-fuchsin and the acid-fast bacilli appears pink, clearly standing out
against a blue background. The carbol-fuchsin can only be removed with acid-alcohol. Acid-fast bacilli can also be seen by using fluorescent microscopy or with auramine-rhosamine stain. M.TB.’s resistance to stains is caused by its cell wall (Wikipedia paragraph 6-7).
The cell wall structure of M.TB. stands out in comparison to other prokaryotes. The cell wall contains peptidoglycan and over 60% of it is lipid. The lipid portion of the cell wall consists of three major components: mycolic acids, cord factor, and Wax-D. “Mycolic acids are alpha-branched lipids found in cell walls of Mycobacterium and Corynebacterium” (Todar, Kenneth paragraph 15). They make up half of the mycobacterial cell envelope. Mycolic acids are hydrophobic molecules that affect the permeability properties of the cell surface, which is why Mycobacterium tuberculosis is difficult to stain. Mycolic acids also prevent attacks by cationic proteins, lysozyme and oxygen radicals in the phagocytic granule. Mycolic acids also protect extracellular mycobacteria from complement deposition in serum. Cord...