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. subtilis and 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