Bacillus anthracis and other bacilli

Question 1

General Features and habitat of Bacillus anthracis

Answer 1

Gram +
Large rods in chains

Habitat- zoonosis (animals), soil, skin

Question 2

Biochemical properties of Bacillus anthracis

Answer 2

Capsule made of proteins- poly-D glutamate
The capsule virulent factor is denoted as pX02
Obligate aerobic (distinguish between clostridium)
Forms spores

Question 3

Pathogenesis of Bacillus anthracis

Answer 3

Toxins: (all 3 must be present to be lethal, denoted as pX01)
− Edema Factor (EF)
Protective Ag (PA) let EF enter the cell → Activate adenylate cyclase → [cAMP] IC increase → edema and impairs macrophages function (allow bacteria to evade the immune system)
− Lethal Factor (LF)
Exotoxin that works as a protease and cleaves MAPK, thus cell growth is disrupted which leads to necrosis

Pulmonary anthrax (Wool Sorter’s disease):
Spores found in soil contaminate animal (wool). Then, they are inhaled by humans. The spores germinate and lead to pulmonary symptoms. This include a dry cough and pulmonary hemorrhage which leads to death

Cutaneous anthrax:
Spores from soil contaminate animals, germinate and proliferate. This leads to formation of painless papules, ulcers with vesicles and eventually necrosis

Gastrointestinal anthrax:
Ingestion of spores (rare) will cause ulcers at site of invasion. Leads to mesenteric lymphadenopathy, abdominal pain, vomiting and later edema, sepsis which results in death

Question 4

Clinical Features of Bacillus anthracis

Answer 4

Black eschar- black necrotic cutaneous lesion with surrounding erythematous ring

Question 5

Diagnosis of Bacillus anthracis

Answer 5

Simple agar (“glass-like” colonies) from smear (of lesion fluid)

Blood agar with no (gamma) Hemolysis (unlike B. cereus)

ELISA of anti-PA IgG or PCR of pX01 / pX02

Question 6

Treatment of Bacillus anthracis

Answer 6

Fluoroquinolones Doxycycline

Question 7

General Features and habitat of Bacillus Cereus

Answer 7

Gram +
Large rods in chains
Habitat- found in nature

Question 8

Biochemical Properties of Bacillus Cereus

Answer 8

No capsule
Fimbriae (pili) and Lecithinase+
Obligate aerobic
Forms spores

Question 9

Pathogenesis of Bacillus Cereus

Answer 9

Food-Poisoning:
• Emetic form
(“short incubation” of 1-6 hours, like S. aureus) by heat-stable enterotoxin-emetic toxin.
From contaminated rice dishes that have been cooked and then held at warm temperature

• Diarrheal form
(“long incubation” of 8-16 hours, like C. perfringens) by heat-labile enterotoxin- activate adenylate cyclase enzymes. From contaminated meat and vegetables

Can cause wound infections by invasion to open wound or traumatic injuries (opportunistic)

Question 10

Clinical Features of Bacillus Cereus

Answer 10

Vomiting, nausea, abdominal cramps and diarrhea

Question 11

Diagnosis of Bacillus Cereus

Answer 11

Simple agar (“cloud-like” colonies)
Blood agar with Beta-Hemolysis
Egg yolk medium (Lecithinase +)

Question 12

Prevention of Bacillus Cereus

Answer 12

Self-limiting

Question 13

Name 3 other spore forming aerobes and antibodies produced

Answer 13

Bacillus subtilis: Bacitracin, Difficidin, Subtilin, Mycobacillin

Paenibacillus polymyxa: Polymyxin, Colistin

Bacillus circulans: Circulin (have occasionally caused gastroenteritis

Question 14

Usage of Geobacillus stearothermophilus

Answer 14

Test heat sterilization procedures