lecture 19 ? bacillus
TRANSCRIPT
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Bacillus
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~ 60 species; Gram-positive or Gram-variable bacilli• Large (0.5 x 1.2 to 2.5 x 10 um)• Most are saprophytic contaminants or normal flora• Bacillus anthracis is most important member
Produce endospores Aerobic or facultatively anaerobic Catalase positive (most)
• Rapidly differentiates from Clostridium Bacillus spp. are ubiquitous• Soil, water, and airborne dust• Thermophilic (< 75°C) and psychrophilic (>5-8°C)• Can flourish at extremes of acidity & alkalinity (pH 2 to 10)
General Characteristics of Bacillus
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Diseases Associated with Bacillus
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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
Laboratory Characteristics of Bacillus
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Bacillus anthracis
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Summary of B. anthracis Infections
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Summary of B. anthracis Infections
(cont.)
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Epidemiology of Bacillus anthracis Rare in the US (1974-1990, 17 cases reported by CDC) Enzootic in certain foreign countries (e.g., Turkey, Iran,
Pakistan,and Sudan) Anthrax spores infectious for decades
• Biologic warfare experiments (annual tests for 20 years) Gruinard, off western coast of Scotland 4 x 10e14 fully virulent spores exploded Eliminated in 1987 (formaldehyde & seawater)
Three well-defined cycles• Survival of spores in the soil• Animal infection• Infection in humans
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Epidemiology of Bacillus anthracis (cont.)
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
• Increased mortality with these portals of entry 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, agricultural workers
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Epidemiology of Anthrax in Animal and
Human Hosts
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Clinical Presentation of Anthrax Cutaneous Anthrax
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
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Clinical Presentation of Anthrax Inhalation Anthrax
Virtually 100% fatal (pneumonic) Meningitis may complicate cutaneous and
inhalation forms of disease Pharyngeal anthrax
• Fever• Pharyngitis• Nneck swelling
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Clinical Presentation of Anthrax Gastrointestinal (Ingestion) Anthrax
Virtually 100% fatal Abdominal pain Hemorrhagic ascites Paracentesis fluid may reveal gram-positive rods
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Treatment & Prophylaxis Treatment
• Penicillin is drug of choice• Erythromycin, chloramphenicol acceptable alternatives• Doxycycline now commonly recognized as
prophylactic
Vaccine (controversial) Laboratory workers Employees of mills handling goat hair Active duty military members Potentially entire populace of U.S. for herd immunity
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Characteristic Bacillus anthracis Other Bacillus spp.Hemolysis Neg PosMotility Neg Pos (usually)Gelatin hydrolysis Neg PosSalicin fermentation Neg PosGrowth on PEAblood agar Neg Pos
Key Characteristics to Distinguish between B. anthracis & Other Species of Bacillus
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Bacillus cereus
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Summary of B. cereus Infections
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Summary of B. cereus Infections (cont.)
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Gram-Variable Stain of B. cereus with Endospores
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Foodborne Diseases of B. cereus (Intoxication) (Foodborne Infection)
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Bacillus thurigensis• BT corn; Other GMO’s (genetically modified organisms)
Bacillus stearothermophilus• Spores used to test efficiency of killing in autoclaves
Other Bacillus spp.
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REVIEWBacillus
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~ 60 species; Gram-positive or Gram-variable bacilli• Large (0.5 x 1.2 to 2.5 x 10 um)• Most are saprophytic contaminants or normal flora• Bacillus anthracis is most important member
Produce endospores Aerobic or facultatively anaerobic Catalase positive (most)
• Rapidly differentiates from Clostridium Bacillus spp. are ubiquitous• Soil, water, and airborne dust• Thermophilic (< 75°C) and psychrophilic (>5-8°C)• Can flourish at extremes of acidity & alkalinity (pH 2 to 10)
General Characteristics of Bacillus
REVIEW
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Diseases Associated with Bacillus
REVIEW
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Review of Bacillus anthracis
REVIEW
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Bacillus anthracis
REVIEW
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Summary of B. anthracis Infections
REVIEW
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Summary of B. anthracis Infections
(cont.)
REVIEW
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Epidemiology of Anthrax in Animal and
Human Hosts
REVIEW
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Clinical Presentation of Anthrax Cutaneous Anthrax
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
REVIEW
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Clinical Presentation of Anthrax Inhalation Anthrax
Virtually 100% fatal (pneumonic) Meningitis may complicate cutaneous and
inhalation forms of disease Pharyngeal anthrax
• Fever• Pharyngitis• Nneck swelling
REVIEW
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Clinical Presentation of Anthrax Gastrointestinal (Ingestion) Anthrax
Virtually 100% fatal Abdominal pain Hemorrhagic ascites Paracentesis fluid may reveal gram-positive rods
REVIEW
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Treatment & Prophylaxis Treatment
• Penicillin is drug of choice• Erythromycin, chloramphenicol acceptable alternatives• Doxycycline now commonly recognized as
prophylactic
Vaccine (controversial) Laboratory workers Employees of mills handling goat hair Active duty military members Potentially entire populace of U.S. for herd immunity
REVIEW
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Review of Bacillus cereus
REVIEW
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Summary of B. cereus Infections
REVIEW
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Summary of B. cereus Infections (cont.)
REVIEW
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Foodborne Diseases of B. cereus (Intoxication) (Foodborne Infection)
REVIEW
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