ppt Lecture 19 ? Bacillus

Lecture 19 ? Bacillus   Size:1.53 M | View:282 | Page:42

~ 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...  
~ 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 (5-8°C) Can flourish at extremes of acidity & alkalinity (pH 2 to 10)General Characteristics of BacillusDiseases Associated with 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 specimensLaboratory Characteristics of BacillusBacillus anthracisSummary of B. anthracis InfectionsSummary of B. anthracis Infections (cont.)Epidemiology of Bacillus anthracisRare 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 humansEpidemiology 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 workersEpidemiology of Anthrax in Animal and Human HostsClinical Presentation of Anthrax Cutaneous Anthrax95% 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 anthraxClinical Presentation of Anthrax Inhalation AnthraxVirtually 100% fatal (pneumonic) Meningitis may complicate cutaneous and inhalation forms of disease Pharyngeal anthrax Fever Pharyngitis Nneck swellingClinical Presentation of Anthrax Gastrointestinal (Ingestion) AnthraxVirtually 100% fatal Abdominal pain Hemorrhagic ascites Paracentesis fluid may reveal gram-positive rodsTreatment & ProphylaxisTreatment 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 immunityCharacteristic Bacillus anthracis Other Bacillus spp. Hemolysis Neg Pos Motility Neg Pos (usually) Gelatin hydrolysis Neg Pos Salicin fermentation Neg Pos Growth on PEA blood agar Neg Pos Key Characteristics to Distinguish between B. anthracis & Other Species of BacillusBacillus cereusSummary of B. cereus InfectionsSummary of B. cereus Infections (cont.)Gram-Variable Stain of B. cereus with EndosporesFoodborne Diseases of B. cereus (Intoxication)(Foodborne Infection) Bacillus thurigensis BT corn; Other GMO’s (genetically modified organisms) Bacillus stearothermophilus Spores used to test efficiency of killing in autoclaves Other Bacillus spp.REVIEW Bacillus~ 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 (5-8°C) Can flourish at extremes of acidity & alkalinity (pH 2 to 10)General Characteristics of BacillusREVIEWDiseases Associated with BacillusREVIEWReview of Bacillus anthracisREVIEWBacillus anthracisREVIEWSummary of B. anthracis InfectionsREVIEWSummary of B. anthracis Infections (cont.)REVIEWEpidemiology of Anthrax in Animal and Human HostsREVIEWClinical Presentation of Anthrax Cutaneous Anthrax95% 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 anthraxREVIEWClinical Presentation of Anthrax Inhalation AnthraxVirtually 100% fatal (pneumonic) Meningitis may complicate cutaneous and inhalation forms of disease Pharyngeal anthrax Fever Pharyngitis Nneck swellingREVIEWClinical Presentation of Anthrax Gastrointestinal (Ingestion) AnthraxVirtually 100% fatal Abdominal pain Hemorrhagic ascites Paracentesis fluid may reveal gram-positive rodsREVIEWTreatment & ProphylaxisTreatment 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 immunityREVIEWReview of Bacillus cereusREVIEWSummary of B. cereus InfectionsREVIEWSummary of B. cereus Infections (cont.)REVIEWFoodborne Diseases of B. cereus (Intoxication)(Foodborne Infection)REVIEW
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Lecture 19 ? Bacillus

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