aerobic bacilli

AEROBIC BACILLUS
? Lecture (14)
? Dr. Baha,H,AL-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 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

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)

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-A capsule of D-glutamic 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) protease that disrupts signaling causing cell death &tissue necrosis

Pathogenesis and clinical presentations
? Cetaceous anthrax
? About 20% mortality

Inhalation anthrax
High mortality

Gastrointestinal anthrax
High mortality

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

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

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

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
? Antibiotic such ciprofloxin ,doxcycline &other are used for treatment