![](/olcweb/styles/shared/spacer.gif) | ![](/sites/dl/free/0072320427/title/cover_image.JPG) Foundations in Microbiology, 4/e Kathleen Park Talaro,
Pasadena City College Arthur Talaro
The Gram-positive Bacilli of Medical Importance
Chapter Overview- Gram-positive bacilli account for a number of significant infectious diseases. General separation into groups can be done according to presence of spores, acid fastness, and cell morphology.
- The major genera of endospore-forming bacilli are Bacillus and Clostridium.
- Members of the genus Bacillus are primarily aerobic soil inhabitants that are noninfectious. The most important pathogen is B. anthracis, the cause of anthrax, a zoonotic disease of livestock.
- Members of the genus Clostridium are anaerobic inhabitants of soil, vegetation, and occasionally normal flora. Their pathogenesis is due to resistant spores and powerful exotoxins and enzymes.
- Clostridial diseases arising from wounds include tetanus, a neuromuscular disease, and gas gangrene, a soft-tissue infection that damages muscles.
- Clostridia are also implicated in food-borne illness, notably botulism, a food intoxication.
- Listeria monocytogenes and Erysipelothrix rhusiopathiae are non-spore-forming rods that can infect humans.
- Listeria is widespread throughout natural habitats and may be ingested in contaminated food. It causes a systemic infection, listeriosis, which can be very serious in babies and the elderly.
- Erysipelothrix causes a zoonosis in pigs and erysipeloid, a skin infection in humans.
- Corynebacterium species are gram-positive pleomorphic rods with palisades arrangement.
- The primary pathogen in the group is Corynebacterium diphtheriae, the agent of diphtheria, a toxin-induced disease of the throat, heart, and nervous system.
- Members of Mycobacterium are acid-fast bacilli with complex lipids in their cell walls.
- The most prominent pathogen worldwide is Mycobacterium tuberculosis, the cause of tuberculosis, a disease spread by respiratory droplets.
- Tuberculosis begins with a lung infection but can progress chronically to other organs. It is diagnosed by skin testing, X ray, and acid-fast staining.
- Mycobacterium leprae is an obligate parasite of humans that is weakly communicable through very close contact.
- The disease leprosy is a slow, progressive infection of skin and nerves that leads to nerve damage, deformities, and thickened nodules in the skin of the face and extremities.
- The gram-positive bacillary diseases for which there is effective vaccination are anthrax, tetanus, diphtheria, and tuberculosis.
|
|