Bacillus anthracis
6,219 views
Bacteria - Gram Positive
- Staph aureus: Overview
- Staph aureus: Presentation
- Methicillin-Resistant Staph aureus (MRSA)
- Staph saprophyticus
- Strep pneumoniae: Overview
- Strep pneumoniae: Presentation
- Strep viridans
- Strep pyogenes: Overview
- Strep pyogenes: Presentation
- Strep agalactiae
- Strep bovis
- Enterococcus
- Bacillus anthracis
- Bacillus cereus
- Clostridium tetani
- Clostridium perfringens
- Clostridium botulinum
- Clostridium difficile
- Corynebacterium diphtheriae
- Listeria monocytogenes
- Nocardia
- Actinomyces
Bacillus anthracis
- Characteristics
- Gram + rod
- Spore-forming
- Survives in soil
- Colonies form a long-chain that is described as being “serpentine”/“medusa head” on appearance. show a halo of projections
- Virulence Factors
- Produces anthrax toxin consisting of 3 parts:
- protective antigen
- binds to cell surface and mediates entry of edema and lethal factor into the cytosol of cells
- lethal factor
- Protease that impairs many cell signalling pathways by cleaving mitogen-activated protein kinase kinases (MAPKK)
- Impairs many cell functions, causing death/necrosis (lethal to cells)
- Responsible for necrosis in ulcers and tissue damage in anthrax infections
- edema factor
- ↑ cAMP levels
- Acts as calmodulin-dependent adenylate cyclase
- Causes accumulation of fluid (edema) in tissues and suppresses innate immune function
- ↑ cAMP levels
- protective antigen
- Polypeptide capsule made of D-glutamate
- Produces an antiphagocytic capsule that is required for pathogenicity. The capsule is unique in that it contains D-glutamate instead of polysaccharide.
- Produces anthrax toxin consisting of 3 parts:
- Exposure
- animals hair/hides/wool
- Goat hair is the most commonly implicated (e.g. woolsorter’s disease)
- Common in areas where animal vaccination rates are low; e.g. developing countries
- bioweapon
- animals hair/hides/wool
- Presentation: Anthrax
- Cutaneous anthrax
- spores introduced into subcutaneous tissue; most common form
- papule → painless necrotic ulcer covered with black eschar
- Formed by release of toxins LF and EF leading to edema and necrosis
- uncommonly progresses to bacteremia and death
- Pulmonary anthrax
- Inhalation of spores; relatively rare (~5% of cases)
- Also known as woolsorter's disease
- flu-like symptoms (myalgia, fever, malaise) → rapidly progress to hemorrhagic mediastinitis (widened mediastinum on X-ray), pulmonary hemorrhage (bloody pleural effusions), septic shock, and death
- Gastrointestinal anthrax
- Ingestion of spores; extremely rare
- Cutaneous anthrax
- Treatment
- Ciprofloxacin or doxycycline for all patients
- Protein synthesis inhibitor
- For systemic anthrax in combination with quinolone or doxycycline
- Reduces toxin production
- Antitoxin for all patients
- Monoclonal antibodies (raxibacumab)
- Anthrax immunoglobulin