24- Bacillus Flashcards
What is the difference between bacillus and clostridium?
Bacillus sp. and Clostridium sp. are both of the same family Bacillaceae, which is the endospore forming bacteria family
Bacillus sp: Aerobic and facultative anaerobic spore formers, nonmotile, non hemolytic gram-positive rod
Clostridium sp: Strict, anaerobic spore formers
What are the 3 proteins of B. anthracis?
Protective Antigen (PA), Edema Factor (EF) and Lethal Factor (LF)
Which of the 2 proteins, when combined, form the edema toxin?
PA + EF
Which 2 proteins, when combined, form the lethal toxin?
PA + LF
What is the function of PA?
PA will attach to one of two receptors on host cell surfaces that are present on many cells and tissues
After PA binds, host proteases cleave PA, releasing a small fragment and retaining a fragment (PA63 as its 63 kDa in weight) on the cell surface
PA fragments self-associate on the cell surface, forming a ring-shaped complex of seven fragments and this heptameric complex can bind up to three molecules of LF and/or EF. Both factors recognize the same binding site of PA63, so the biding is competitive.
Formation of the complex stimulates endocytosis and movement to an acidic compartment.
In this environment the heptameric complex forms a transmembrane pore and releases LF and EF into the cell cytosol
What is the function of LF?
LF is a zinc-dependent protease that is capable of cleaving mitogen-activated protein kinase, leading to cell death.
What is the function of EF?
EF is a calmodulin-dependent adenylate cyclase that increases the intracellular cyclic adenosine monophosphate (cAMP), resulting in edema
B. anthracis- epidemiology
It primarily infects herbivores, with humans as accidental hosts via exposure.
Rarely isolated in developed countries but is prevalent in improverished area where vaccinated of animals is not practiced. The greatest danger of anthrax in industrial countries is the use of B anthracis as an agent of bioterrorism
What are the 3 routes of B. anthracis to infect?
One being inoculation which approximately 95% of anthrax infections in humans result from the inoculation of Bacillus spores through exposed skin from either contaminated soil or infected animal products such as hide, goat hair, or wool
Ingestion is the second route and is very rare in humans but occurs more in herbivores and is the more common of routes. The
Inhalation is historically is called wool-sorters’ disease because most infections resulted from acquiring spores during the processing of goat hair
most likely route of infection with biological weapons and the infectious dose of the organism is believed to be low which makes it appealing to be weaponized by terror groups and organizations for biological warfare.
What is the clinical presentation of an inoculation exposure of B. anthracis?
Most common way to get anthrax infection through exposed skin from either contaminated soil or infected animal products such as hides, goat hair and wool
Cutaneous anthrax starts with the development of a painless papule at the site of inoculation that rapidly progresses to an ulcer surrounded by vesicles, the to a necrotic eschar
Systemic signs, painful lymphadenopathy, and massive edema may develop. The mortality rate in patients with untreated cutaneous anthrax is 20%.
What is the clinical presentation of ingestion exposure of B. anthracis?
Very rare in humans but common for herbivores.
GI anthrax clinical symptoms are determined by the site of the infection
If organisms invade the upper intestinal tract, ulcers form in the mouth or esophagus, leading to regional lymphadenopathy, edema, and sepsis
If the organism invades the cecum or terminal ileum, the patient presents with nausea, vomiting, and malaise, which rapidly progress to systemic disease
Mortality rate associated with GI anthrax is believed to approach 100%.
What are the clinical findings of inhalation exposure of B. anthracis?
Initial clinical symptoms are nonspecific—fever, myalgias, nonproductive cough, and malaise
Second stage of the disease is more dramatic, with a rapidly worsening course of fever, edema, massive enlargement of the mediastinal lymph nodes (this is responsible for a widened mediastinum observed on a chest radiography), respiratory failure, and sepsis
Pneumonia is rarely seen in patients with inhalation anthrax but more than half of patients present with meningeal symptoms
Almost all cases progress to shock and death within 3 days of initial symptoms unless anthrax is suspected and treatment is initiated immediately.
What are the 2 forms of gastroenteritis from B. cerus exposure?
Emetic and diarrheal
What is the epidemiology of emetic gastroenteritis of B. cerus exposure?
Contaminated rice that is not refrigerated, as most the bacteria is killed during initial cooking, allows the spores to germinated and multiply rapidly
The heat-stable enterotoxins that is released is not destroyed when the rice is reheated.
Emetic B. cerus- clinical significance
Symptoms include vomiting, nausea, and abdominal cramps. No fever and diarrhea.
