Causative Agent

Today, most cases of tuberculosis are caused by Mycobacterium tuberculosis, although in the years before widespread milk pasteurization, the cattle-infecting species Mycobacterium bovis was a common cause. Mycobacterium tuberculosis, commonly called the tubercle bacillus, is a slender acid-fast, rod-shaped bacterium (figure 23.17). The organismis a strict aerobe that grows very slowly, with a generation time of 12 hours or more. This slow growth makes it difficult to diagnose tuberculosis quickly. Although easily killed by pasteurization, the tubercle bacillus is unusually resistant to drying, disinfectants, and strong acids and alkali. The bacterium has a Gram-positive cell wall, but bound covalently to the cell wall peptidoglycan is a thick layer composed of complex glycolipids, and other lipids compose much of the bacterial surface. Up to 60% of the dry weight of the M. tuberculosis cell wall consists of lipids, a much higher percentage than that in most other bacteria. The lipid-containing cell wall is largely responsible for its acid-fast staining, resistance to drying and disinfectants, and its pathogenicity. ■ pasteurization, p. 114 ■ lipids, p. 33

Was this article helpful?

0 0
How To Get Rid Of Yeast Infections Once And For All

How To Get Rid Of Yeast Infections Once And For All

No more itching, odor or pain or your money is refunded! Safe and DRUG FREE Natural Yeast Infection Solutions Are you looking for a safe, fast and permanent cure for your chronic yeast infection? Get Rid of that Yeast Infection Right Now and For Good!

Get My Free Ebook

Post a comment