Gram Positive Bacilli

Front 1

Spore Forming Rods

Back 1

Bacillus and Clostridium
 Release of potent exotoxins causes disease

Front 2

Bacillus anthracis

Back 2

Causative agent of anthrax
 UNIQUE protein capsule, antiphagocytic
 Aerobic growth conditions
 Spores are very stable, resistant to heat, drying, UV and
disinfectants; spores germinate and toxins are made
 Humans exposed to spores usually through contact with animals or
soil
 Used in bio-terrorism and warfare

Front 3

Bacillus anthracis exotoxin

Back 3

Encoded on pXO1 plasmid
 Plasmid contains virulence factors which are transcribed optimally
@ 37 C, increased CO2 and serum proteins
 ?? Where are these conditions found ??
 Exotoxin composed of 3 separate proteins:
 Edema factor (EF)
 Protective antigen (PA)
 Lethal factor (LF)
 Separately proteins are not toxic, but combined are lethal
 pXO2 plasmid encodes capsule genes
 **BOTH plasmids required for virulence**

Front 4

Prevention and Treatment of Bacillus antracis

Back 4

 RAPID treatment is essential
 Antibiotics: penicillin, doxycyclin, ciprofloxacin or levofloxacin
 Vaccine against PA protein is available

Remember: capsule protects AND is made of protein
 cutaneous and respiratory routes for spores
 animal hides and/or soil

Front 5

Bacillus cereus

Back 5

Causes food poisoning when spores enter food product
 Motile, non-encapsulated, resistant to penicillin
 ENTEROTOXIN is responsible for illness
 2 types of enterotoxin
(i) Heat labile: nausea, abdominal pain, diarrhea. Lasts 12-24hrs
(ii) Heat stable: SEVERE nausea and vomiting, short incubation
 Antibiotic treatment useless….preformed toxins

Front 6

Clostridium

Back 6

 Anaerobic > differentiates this bacteria from other
spore-forming bacilli
 Botulism, tetanus, gas gangrene and pseudomembranous
colitis
 POWERFUL EXOTOXINS RAPID DIAGNOSIS

Front 7

Clostridium botulinum

Back 7

Rapidly fatal food poisoning from lethal neurotoxin
 Neurotoxin blocks Ach release in autonomic system; flaccid
muscle paralysis:
Afebrile, bilateral cranial nerve palsies, double vision,
trouble swallowing, muscle weakness
Respiratory paralysis DEATH
Treatment: antitoxin and respiratory assistance
 Smoked fish, improperly canned vegetables
Proper cooking destroys spores

Front 8

Action of Botulinum Neurotoxin

Back 8

Botulism toxin inhibits the release of acetylcholine, not allowing the muscle to contract.

Front 9

Infant Botulism

Back 9

Honey contamination with spores
Spores germinate and bacteria colonizes
intestine
Neurotoxin release
2-3 days of constipation
Trouble swallowing, muscle weakness

Front 10

Clinical Manifestations of Clostridium botulinum

Back 10

1. entry
2. absorption
3. spread of toxin
4. disease (flaccid paralysis)

Front 11

Clostridium tetani

Back 11

Tetanus
 Rusty nail contaminated with spores punctures
skin; wound provides anaerobic environment
 Exotoxin: tetanospasmin
Sustained contraction of skeletal muscles
Severe muscle spasms (lock jaw); high
mortality at this stage
 Booster (inactivated toxoid) given every 10 years

Front 12

Clinical Manifestations of Clostridium tetani

Back 12

1. entry
2. spread of toxin
3. no exit
4. disease (rigid paralysis, jaw locked, cardiac failure, respiratory failure)

Front 13

Clostridium perfringens

Back 13

Gas gangrene
 Seen in soldiers wounded in battle

Front 14

2 classes of clostridium perfringens infection

Back 14

i) Wound infection/cellulitis
-necrotic skin exposed to bacteria, damage to local
tissues; skin feels moist, spongy, with ‘crackly’ pockets
(ii) Clostridial myonecrosis
-bacteria inoculated from trauma into muscles; exotoxin
secretion destroys adjacent muscles; as muscles degrade get
black fluid excreeted from skin
-FATAL unless treated with oxygen, antibiotics
(penicillin) and removal of damaged tissue

Front 15

Clostridium difficile

Back 15

Causes antibiotic-associated
pseudomembranous colitis
 Seen more commonly in hospitals than tetanus,
anthrax or botulism
 Overuse of broad-spectrum antibiotics destroys
normal intestinal flora
 Infects colon and releases exotoxins
Toxin A: diarrhea
Toxin B: cytotoxic to colon cells

Front 16

Clostridium difficile symptoms and treatment

Back 16

Symptoms: severe diarrhea, abdominal cramping, fever
 Possible cause of diarrhea in patients on antibiotics
 Treatment
discontinue antibiotic treatment
Administer metronidazole or vancomycin

Front 17

Clinical manifestations of Clostridium
difficile

Back 17

1. entry
2. spread
3. disease

Front 18

Non-Spore Forming Rods

Back 18

2 medically important bacilli
Listeria monocytogenes and
Corynebacterium diptheriae

Front 19

Listeria monocytogenes

Back 19

Causative agent of listeriosis; immunocompromised are at
high risk
 Found in foods such as soft cheeses, unpasteurized milk, cold
cuts, pâté
 PSYCHROPHILE survives in refrigerator
 Variety of symptoms:
General malaise, diarrhea, meningitis, septicaemia,
still-birth/abortions
 Facultative intracellular aerobe
 Crosses 3 protective barriers (blood-brain, GI and fetoplacental)
 Treatment: ampicillin or trimethoprim-sulfamethoxazole

Front 20

Clinical Manifestations of Listeria
monocytogenes

Back 20

1. entry
2. invasion
3. spread
4. disease (meningitis, endocarditis)
5. exit

Front 21

Corynebacterium diptheriae

Back 21

Causative agent of diptheria
Colonization of pharynx and release of exotoxins into
bloodstream
 Exotoxin damages heart and neural cells
 Treatment (3 steps):
(i) Antitoxin
(ii) Penicillin or erythromycin
(iii) DPT vaccine
 Can be lysogenized by a bacteriophage (virus that infects
bacteria)

Front 22

Clinical manifestations of C. diptheriae

Back 22

1. entry
2. spread
3. disease
4. exit