1. Gram positive Bacilli

4. Bacillus

5. Bacillaceae family • The genera Bacillus and Clostridium belong to the same family • Spore forming bacteria • Natural habitat is soil

6. Genus Bacillus • Gram-positive rod • Obligate aerobes (catalase positive) • Ubiquitous in nature • Both free-living and pathogenic species • Oval endospores

7. Genus Bacillus

8. Clinical significance • B. anthracis(anthrax) • B. cereus (food poisoning) • B. subtilisand B. coagulans(food spoiler)

9. Morphology • Colonies are: • Usually large • Spreading • Irregular

10. B. cereus B. anthracis

11. Bacillus anthracis (Anthrax)

12. Bacillus anthracis • Natural habitat soil • Anthrax is an animal infections • Anthrax is recognized as an occupational disease • Human infection by contact with: • Sick animals • Contaminated animal products

13. Morphology and culturing • 1 µm wide and 2–4 µm long • Non-flagellated • Capsulated (a glutamic acid polypeptide)

15. Pathogenesis of Anthrax • Anti-phagocytic capsule • Toxin (causes edemas and tissue necrosis)

16. Types of infections • Dermal anthrax (95% of cases) • Primary inhalational anthrax • Intestinal anthrax (vomiting and bloody diarrheas)

17. Laboratory diagnosis • Specimens should be handled in a Bio-safety level 3 facility • Gram stain shows gram-positive bacilli • In advanced disease, a gram stain of un-spun blood may be positive

18. Identification of B. anthracis • Non-hemolytic, non-motile, capsulated bacteria • ELISA and PCR tests are available at reference laboratories

19. Lysis of Bacillus anthracis by the lytic phage gamma

20. Treatment • Drug of choice is penicillin G • Doxycycline or ciprofloxacin are possible alternatives

21. End of this section