AEROBIC BACILLUS Lecture (14) Dr. Baha,H,AL-Amiedi Amiedi Ph.D.Microbiology
General Characteristics of 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 Bacillus anthracis Human pathogen Isolation also considered to be clinically significant Zoonosis Bacillus cereus Environmental organism Contaminates food Common cause of food poisoning Bacillus stearothermophilus Tolerates very high temperatures Used for quality control of autoclaves Used for quality control of autoclaves
Bacillus anthracis 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 Thermophilic (< 75 C) and psychrophilic (>5-8 C) Can flourish at extremes of acidity & alkalinity (ph 2 to 10)
.Bacillus anthracis
B. anthracis
Diseases Associated with Bacillus
Summary of B. anthracis Infections
Transmission: 1-cutaneous anthrax result from contact with spores & contact with infected animals & animals products. 2-inhalation anthrax result when spores inhaled. 3-Gastrointestinal anthrax result when spores are ingested.
Virulence factors 1-AA capsule of D-glutamicD acid is antiphagocytic and helps the anthracis to evade the immune system of the host. 2-The product of exotoxin
Mode of toxin action Three exotoxins subunit are product: 1-protctive Antigen(PA):binds to toxin receptor on cell surface of host &facilitates translocation of the two other exotoxins, 2-Edema Factor(EF): is an adenlyate cyclase that increase intracellular camp Stimulating effuision of fluids &ion that result the edema.
3-Lethal Factor(LF):it is a mitogen-activted protein kinase kinase(mapkk disrupts signaling causing cell death &tissue necrosis kinase(mapkk) ) protease that
Pathogenesis and clinical presentations Cutaneous anthrax About 20% mortality Inhalation anthrax High mortality Gastrointestinal anthrax High mortality
Pathogenesis of Anthrax
Clinical Presentation of Anthrax Cutaneous Anthrax 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
Anthrax: Cutaneous
Anthrax: Cutaneous
Anthrax: Cutaneous
Anthrax: Cutaneous
Clinical Presentation of Anthrax Inhalation Anthrax Virtually 100% fatal (pneumonic) Meningitis may complicate cutaneous and inhalation forms of disease Pharyngeal anthrax Fever Pharyngitis Neck swelling
Inhalational Anthrax
Mediastinal Widening and Pleural Effusion on Chest X-RayX in Inhalational Anthrax
Clinical Presentation of Anthrax Gastrointestinal (Ingestion) Anthrax Virtually 100% fatal Abdominal pain Hemorrhagic ascites Paracentesis fluid may reveal gram-positive rods
Epidemiology of Bacillus anthracis Enzootic in certain foreign countries (e.g., Turkey, Iran, Pakistan,and Sudan) Anthrax spores infectious for decades
Epidemiology of Anthrax in Animal and Human Hosts
B. anthracis
.Bacillus cereus Pre formed Large, motile, saprophytic Heat resistant spores heat and acid stable toxin (Emetic syndrome) bacillus Heat labile enterotoxin (Diarrhoeal disease) Lab diagnosis Demonstation of large number of bacilli in food
Gastroenteritis Gastroenteritis EMETIC FORM DIARRHOEAL FORM Incubation period < 6 hours Severe vomiting Lasts 8-10 hours Incubation period > 6 hours Diarrhoea Lasts 20-36 hours
Laboratory diagnosis B. Anthrax: 1-Microscopic Examination Smear prepared from exudates,sputum show gram positive bacilli non- occur in chain 2-Macfadyen test; it is special stain for capsular of bacilli 3-Seriological test (Ascoli test): it is rapid precipitate diagnosis test.
Ascoli test It is rapid diagnosis of B.anthrax,the infected tissues are grounded in saline boiled for 5 minutes & filtered. extracted tissue is layered over anthrax antiserum. Zone of precipitate at the junction of tissue extract and antiserum within 5 minutes at room temperature means test is positive.
4-Cultur ;On blood agar Large, spreading, gray-white colonies, with irregular margins (Medosa head shape) Many are beta-hemolytic (helpful in differentiating various Bacillus species from B. anthracis) Spores seen after several days of incubation in central by smear gram stain examine,
5-Animal inoculation: injected guinea pig subcutaneously which die within 36-48 hours,smear from Heart blood &spleen show gram positive bacilli.
Treatment Treatment Antibiotic such ciprofloxin,doxcycline &other are used for treatment