Bacillus is a genus of gram-positive, spore-forming bacteria that are ubiquitous in the environment. Some Bacillus species are pathogenic to humans and animals, including B. anthracis, which causes anthrax, and B. cereus, which can cause food poisoning. B. anthracis forms durable spores that allow the bacteria to survive for decades in the environment. It causes anthrax, which presents as one of three forms: cutaneous, inhalation, or gastrointestinal. The inhalation form is often fatal if untreated. B. cereus can cause two types of food poisoning - an emetic type or diarrhea type - through the production of enterotoxins. While most Bacillus
3. Characters of Bacillus
Gram-positive or Gram-variable bacilli
Aerobic, spore forming
Large number of species are saprophytes, antharcoides
Ubiquitous
Some are motile and some capsulated
non-pathogenic organisms is B. subtilis-subtilis group
B. mycoides,
B.megaterium,
B.cereus
Natural habitats:
Water, soil, decaying matter, dust, air
Pathogenic species—B.anthracis
4. Laboratory Characteristics of Bacillus
On blood agar
Large, spreading, gray-white colonies, with irregular
margins
Many are beta-hemolytic (helpful in differentiating
various Bacillus species from B. anthracis)
Spores seen after several days of
incubation, but not typically in fresh clinical
specimens
5. Epidemiology of Bacillus anthracis
Enzootic in certain countries (e.g., Turkey, Iran,
Pakistan and Sudan)
Anthrax spores infectious for decades
Biologic warfare experiments
Primarily a disease of herbivorous animals
Most commonly transmitted to humans by direct
contact with animal products (e.g., wool and hair)
Also acquired via inhalation & ingestion
6. Still poses a threat
Importing materials
contaminated with
spores from these
countries (e.g., bones,
hides, and other
materials)
Usually encountered as
an occupational
disease
Veterinarians
7. Cultural Characteristics
Grows rapidly on ordinary
lab. Media
Nutrient agar,
blood agar,
serum agar
Aerobic
Temp 35-37 O
C/24 h
Sporulation under aerobic
conditions at 15-40O
C
Pink—purple pigment
production in the medium
containing iron salts
8. On NA, flat, frosted appearance colony
Roughened edge (Medusa head)
On serum agar; smooth, mucoid colonies
In Nutrient broth; flocculent deposits of long
chains
On blood agar; slight hemolysis
9. Biochemical Characters/ Reactions
Acid without gas (glu, mal, Saccharose)
Nitrate to nitrites
Indole not produced
VP +ve
Resistance
Vegetative killed at 600
C/ 30 minutes
Spore resist
Formaldehyde effective
10. Antigens and Toxins
Capsular polypeptide, somatic protein and
somatic polysaccharide antigen
Extra-cellular toxin composed of three
components;
Factor I, II and III
Oedema factor
Protective factor
Lethal factor, respectively)
Protective antigen binds to cell surface and
functions as receptors for oedema factor and
lethal factor
11. Epidemiology and pathogenesis
Anthrax disease (wool sorter’s disease)
Pulmonary
Skin form
Incidence high in grazing animals, ingest
spores. Spores go to Lymphoid glands
(through any injury)
Death due to shock, renal failure and terminal
anoxia
Two forms
Peracute
Acute
12. In peracute death in 1-2 hours without
symptoms
In acute, eithir 48 hrs
Important charc, tarry blood from natural
orifices (Nostrils, mouth, vagina and anus)
No clotting of blood
Absence of rigor mortis
Splenomegaly
Postmortem?
13. Clinical presentation of anthrax
Cutaneous form
95% human cases are cutaneous infections
1 to 5 days after contact
Small, pruritic, non-painful papule at inoculation site
Papule develops into hemorrhagic vesicle & ruptures
Slow-healing painless ulcer covered with black eschar
surrounded by edema
Infection may spread to lymphatics w/ local
adenopathy
Septicemia may develop
20% mortality in untreated cutaneous anthrax
14. Inhalation anthrax
Virtually 100% fatal
(pneumonic)
Meningitis may
complicate
cutaneous and
inhalation forms of
disease
Pharyngeal anthrax
Fever
Pharyngitis
neck swelling
18. Other species
Bacillus thurigensis
BT cotton Other GMO’s (genetically modified
organisms)
Bacillus stearothermophilus
Spores used to test efficiency of killing in autoclaves