Gram + Bacilli of Medical Importance
Bacillus
Characteristic
• Gram-positive, endospore-forming, motile rods
• Mostly saprobic (environmental organism)
• Aerobic and catalase positive
• Versatile in degrading complex macromolecules.
• Source of antibiotics (produced antibiotic) by Bacillus subtilis
• Primary habitat is soil.
2 species of medical importance:
• Bacillus anthracis cause anthrax
• Bacillus cereus cause food poisoning
Robert Koch & Bacillus anthrax
• Robert Koch worked with for his postulates and used to prove germ theory – germs are the
cause of many diseases.
Virulence factors –
• Encapsulated for protection.
• Exotoxins production
• spore-forming (Except in living body)
• facultative anaerobe (can grow with/without oxygen)
Bacillus anthracis – bacteria responsible for anthrax
Occurrence:
• Most case occur in herbivores from Africa, Asia, Haiti, and Middle Eastern countries.
• Products from these animals may contain spores.
• 20k-100k human cases:
o In U.S., less than 10 human cases/year due to effective control measures but epizootic outbreaks occur
regularly.
• Vaccination of workers involved in the industrial processing of imported animal products and the decline in using
fibers of animal origin à has helped prevent exposure to spores.
Control and Treatment –
• Antibiotics:
o treated with penicillin, tetracycline, or ciprofloxacin.
• Vaccination:
o given live spores and toxoid vaccines to protect livestock against anthrax.
o given purified toxoid vaccine consisting of six inoculations over 1.5yrs + annual boosters to maintain immunity
for high-risk occupations and military personnel.
Clinical forms of anthrax
There are three clinical manifestations dependent on portal of entry:
1. Cutaneous Anthrax – spores enter through skin.
2. Pulmonary Anthrax – inhalation of spores.
3. Gastrointestinal Anthrax – ingested spores.
, 1) Cutaneous Anthrax:
o Spores enter skin through small cuts when handling animal hides or hair.
o SX: growth of microbe in skin causes a small papule that progresses to a black, swollen, crusty ulcer = eschar
o Can be fetal with toxemia and septicemia.
2) Pulmonary Anthrax – “Woolsorter’s disease”
o Inhaled spores germinate in the lungs.
à Vegetative cells grow and produce exotoxins.
à Resulting toxemia causing capillary thrombosis and cardiovascular shock
à Septicemia causes death within a few hours.
o Symptoms:
à Early symptoms: fatigue, malaise, fever, aches, and cough.
à Late symptoms: high fever, labored breathing, and shock.
o Diagnosis:
à Source of infection: cultured from soil, cutaneous lesions, respiratory tract, or blood (+/- of exotoxin)
à Antibiotic treatment: Ciprofloxacin – effective antibiotic against bacillus anthracis but does not counteract
the toxin (not neutralize the exotoxin produced by the bacteria)
à Vaccination: Toxoid (biothrax) administered to humans
à Preventative measures:
¨ Sterilization of hides, hair, and bone products of herbivorous livestock
¨ burn carcasses of livestock that die from anthrax to prevent environment spread.
¨ Administer immunization to susceptible hosts.
3) Gastrointestinal Anthrax
o Rarest form (Not been reported in U.S.
o Occurs in underdeveloped countries when food (milk, cheese, or meat) contaminated with spores is ingested.
o Exotoxins produced in the digestive tract causes necrotic lesion of ileum and/or large intestine.
o Fetal septicemia occurs within hours after the bacterium reaches the lymph and/or bloodstream.
Bacillus cereus – bacteria responsible for food poisoning
Type of bacteria:
• large, spore-forming bacterium
• gram-positive (thick cell wall, appears purple)
• A saprobe that lives in the soil (organism feeds on dead or decaying organic matter)
Characteristic:
• Cause of food poisoning due to contamination of food
• Bacillus cereus is a common airborne and dust-borne contaminant (easily spread through air or dust particles and
contaminate surface of food)
• This bacterium preferred cooked foods such as rice, potato, and meat dishes, where it can grow and produce
enterotoxin.
Symptoms: vomiting and diarrhea
Other infections it can also cause:
• Nosocomial infections
• Can be serious and leads to progressive pneumonia, fulminant sepsis, and central nervous system in the
immunosuppressed, IV drug users, and neonate.
Bacillus
Characteristic
• Gram-positive, endospore-forming, motile rods
• Mostly saprobic (environmental organism)
• Aerobic and catalase positive
• Versatile in degrading complex macromolecules.
• Source of antibiotics (produced antibiotic) by Bacillus subtilis
• Primary habitat is soil.
2 species of medical importance:
• Bacillus anthracis cause anthrax
• Bacillus cereus cause food poisoning
Robert Koch & Bacillus anthrax
• Robert Koch worked with for his postulates and used to prove germ theory – germs are the
cause of many diseases.
Virulence factors –
• Encapsulated for protection.
• Exotoxins production
• spore-forming (Except in living body)
• facultative anaerobe (can grow with/without oxygen)
Bacillus anthracis – bacteria responsible for anthrax
Occurrence:
• Most case occur in herbivores from Africa, Asia, Haiti, and Middle Eastern countries.
• Products from these animals may contain spores.
• 20k-100k human cases:
o In U.S., less than 10 human cases/year due to effective control measures but epizootic outbreaks occur
regularly.
• Vaccination of workers involved in the industrial processing of imported animal products and the decline in using
fibers of animal origin à has helped prevent exposure to spores.
Control and Treatment –
• Antibiotics:
o treated with penicillin, tetracycline, or ciprofloxacin.
• Vaccination:
o given live spores and toxoid vaccines to protect livestock against anthrax.
o given purified toxoid vaccine consisting of six inoculations over 1.5yrs + annual boosters to maintain immunity
for high-risk occupations and military personnel.
Clinical forms of anthrax
There are three clinical manifestations dependent on portal of entry:
1. Cutaneous Anthrax – spores enter through skin.
2. Pulmonary Anthrax – inhalation of spores.
3. Gastrointestinal Anthrax – ingested spores.
, 1) Cutaneous Anthrax:
o Spores enter skin through small cuts when handling animal hides or hair.
o SX: growth of microbe in skin causes a small papule that progresses to a black, swollen, crusty ulcer = eschar
o Can be fetal with toxemia and septicemia.
2) Pulmonary Anthrax – “Woolsorter’s disease”
o Inhaled spores germinate in the lungs.
à Vegetative cells grow and produce exotoxins.
à Resulting toxemia causing capillary thrombosis and cardiovascular shock
à Septicemia causes death within a few hours.
o Symptoms:
à Early symptoms: fatigue, malaise, fever, aches, and cough.
à Late symptoms: high fever, labored breathing, and shock.
o Diagnosis:
à Source of infection: cultured from soil, cutaneous lesions, respiratory tract, or blood (+/- of exotoxin)
à Antibiotic treatment: Ciprofloxacin – effective antibiotic against bacillus anthracis but does not counteract
the toxin (not neutralize the exotoxin produced by the bacteria)
à Vaccination: Toxoid (biothrax) administered to humans
à Preventative measures:
¨ Sterilization of hides, hair, and bone products of herbivorous livestock
¨ burn carcasses of livestock that die from anthrax to prevent environment spread.
¨ Administer immunization to susceptible hosts.
3) Gastrointestinal Anthrax
o Rarest form (Not been reported in U.S.
o Occurs in underdeveloped countries when food (milk, cheese, or meat) contaminated with spores is ingested.
o Exotoxins produced in the digestive tract causes necrotic lesion of ileum and/or large intestine.
o Fetal septicemia occurs within hours after the bacterium reaches the lymph and/or bloodstream.
Bacillus cereus – bacteria responsible for food poisoning
Type of bacteria:
• large, spore-forming bacterium
• gram-positive (thick cell wall, appears purple)
• A saprobe that lives in the soil (organism feeds on dead or decaying organic matter)
Characteristic:
• Cause of food poisoning due to contamination of food
• Bacillus cereus is a common airborne and dust-borne contaminant (easily spread through air or dust particles and
contaminate surface of food)
• This bacterium preferred cooked foods such as rice, potato, and meat dishes, where it can grow and produce
enterotoxin.
Symptoms: vomiting and diarrhea
Other infections it can also cause:
• Nosocomial infections
• Can be serious and leads to progressive pneumonia, fulminant sepsis, and central nervous system in the
immunosuppressed, IV drug users, and neonate.
