GRAM POSITIVE RODS. PART 1 Flashcards
ANTHRAX
Mention 4 medically important gram positive rods
- Bacillus
- Clostridium
- Corynebacterium
- Listeria
which medically important gram positive rods forms spores
- Bacillus
- Clostridium
which medically important gram positive rods are non spore forming
- Corynebacterium
- Listeria
Mention two (2) medically important bacillus species
- Bacillus anthracis
- Bacillus cereus
What disease is caused by bacillus anthracis
Anthrax
Mention the main forms in which human anthrax manifests
- Cutaneous
- Pulmonary (inhalation)
- Gastrointestinal
explain the morphology of bacillus anthracis
B. anthracis is a large gram-positive rod with square ends frequently found in chains
what are the 2 characteristics of bacillus anthracis
- Its antiphagocytic capsule is composed of D-glutamate (capsules of other bacteria are polysaccharides)
- It is nonmotile
How do spores of the anthrax organism persist in the environment?
Anthrax spores can persist in soil for years
What causes cutaneous anthrax infections?
Cutaneous anthrax infections occur when there is trauma to the skin (e.g., cuts, abrasions)
This allows the spores present on animal products (such as hides, bristles, and wool) to enter the body
What is pulmonary (inhalation) anthrax?
- Pulmonary anthrax occurs when anthrax spores are inhaled into the lungs.
- It is not communicable from person to person (i.e., it does not spread directly between individuals).
How does gastrointestinal anthrax occur?
ingesting contaminated meat.
What is the basis of anthrax pathogenesis?
involves the production of two exotoxins: edema factor and lethal factor.
What are the components of the anthrax exotoxins
Each anthrax exotoxin consists of two proteins arranged in an A–B subunit configuration.
The B subunit (binding subunit) in both exotoxins is called “protective antigen.”
The A subunit (active subunit) has enzymatic activity.
What does edema factor do
Edema factor is an adenylate cyclase.
It causes an increase in the intracellular concentration of cyclic adenosine monophosphate (cAMP).
This leads to an outpouring of fluid from the cell into the extracellular space, resulting in edema.
Edema toxin may also increase host susceptibility to infection by disrupting the cytokine response of monocytes and suppressing neutrophil functions.
What is the role of lethal factor?
~Lethal factor is a protease.
~It cleaves the phosphokinase that activates the mitogen-activated protein kinase (MAPK) signal transduction pathway.
~By inhibiting this pathway, lethal factor affects cell growth.
How does protective antigen contribute to anthrax pathogenesis?
Protective antigen forms pores in the human cell membrane.
These pores allow edema factor and lethal factor to enter the cell.
The name “protective antigen” refers to the fact that antibodies against this protein can protect against disease.
Clinical manifestations of anthrax
- A skin lesion
- A respiratory illness
- Abdominal distress
(90% are cutaneous anthrax)
What is Cutaneous Anthrax?
Cutaneous anthrax is a type of anthrax infection that affects the skin.
It occurs when spores of the bacterium Bacillus anthracis infect the skin.
What are the stages of Cutaneous Anthrax?
Papule: Initially, a small, raised bump (papule) forms at the site of infection
Vesicle: The papule develops into a fluid-filled blister (vesicle).
Malignant Pustule: The vesicle becomes a painful, pus-filled sore (malignant pustule).
Necrotic Ulcer: Eventually, the pustule ulcerates, forming a necrotic (dead tissue) ulcer
How do most cases of Cutaneous Anthrax resolve
Approximately 80-90% of cutaneous anthrax cases heal spontaneously within 2-6 weeks
What percentage of cases progress to a more severe form of the disease?
0-20% of cutaneous anthrax cases progress to a more severe form
What happens if cutaneous anthrax is left untreated?
Untreated cases of cutaneous anthrax can lead to death.
What proportion of all human anthrax cases are cutaneous anthrax?
95-99% of all human anthrax cases occur as cutaneous anthrax.
