Lecture 7 Gram positive bacilli Flashcards
What features are gram positive rods classified with?
Their relationship with oxygen
Endospore formation
Morphology: regular, irregular, or filamentous and branching
How does oxygen affect gram positive rods?
Some are aerobes and/or facultative anaerobes
Some are strictly anaerobic
How do gram positive rods differ in endospore formation?
Some are endospore forming
Some are non-endospore forming
What can be said about bacillus oxygen usage and endospore formation?
Bacillus species are both endospore forming and aerobic
How many species are there of bacillus?
> 60
What can be said about the ecological niches of bacillus?
Very diverse ecological niches
Are bacillus species harmful to humans?
most species are non-pathogenic
What are the members of the bacillus cereus group?
IMPORTANT:
[Bacillus cereus
Bacillus thuringiensis
Bacillus anthracis]
GOOD FOR EXTRA MARKS:
Bacillus wiehenstephanensis
Bacillus mycoides
Bacillus pseudomycoides
What do molecular studies reveal about the bacillus cereus group?
They are part of the same species. Their phenotypic differences are caused by plasmid genes.
What does bacillus cereus do?
Food poisoning (caused by reheating of rice dishes)
Produced by enterotoxins
Associated with reheated rice dishes
What is bacillus thuringiensis used for?
Used as an insecticide
Used to control “river blindness” which is caused by onchocerca volvulus and simulium “black flies”
How does bacillus thuringiensis carry out the action it is used for?
Produces protein crystals which destroy the gut function of certain insects.
The code for these protein crystals is found on cry genes
What genes are derived from bacillus that can be used in crop genomes to make them insect resistant?
cry genes (500 differnet genes)
What is bacillus anthracis?
Soil organism that causes zoonotic infection in sheep, goats, horses, and wild animals
How is bacillus anthracis distributed?
Worldwide where it is mostly sporadic in occurrence but in some places it is hyperendemic
Where is anthrax typically found in Australia?
Around the anthrax belt through central NSW and in some locations of Victoria remains the main focus of human and animal cases in Australia.
What are the main virulence factors of bacillus anthracis?
Capsules that protect from host’s immune system
Spores that maintain survival in the environment in infective form which may remain viable for >100 years
How do humans get anthrax?
Humans acquire it when they come in contact with infected animals, their meat or other animal products
What are the transmission routes of anthrax?
Cutaneously through breaks in the skin
Inhalational through aerosols or dust
Ingestion through contaminated meat
What are potential complications of bacillus anthracis?
Could cause meningitis and septicaemia
What is the most common form of anthrax?
Cutaneous anthrax
How do bacillus transition in their lifecycle?
papulae -> Vesicles -> ulcer -> eschar
What percentage of people infected with cutaneous anthrax end up dying from it?
Untreated mortality is 10 - 40% of individuals
What is an eschar?
A black scar which has a ring of cellulitis around it
What parts of the body does inhalational anthrax damage?
Haemorrhagic necrosis of perihilar and other lymph nodes.
What does skin look like that is infected by anthrax?
An eschar forms with red cellulitis around the ring
What is the mortality percentage of people infected by inhalational anthrax?
If not treated it kills 100% of people
What are the symptoms of GI anthrax?
causes inflammation, swelling and haemorrhage from mouth to caecum
What percentage of people affected by GI anthrax die from it?
Up to 50%
What can be said about oxygen usage capacity and spore formation of clostridium species?
They are endospore forming anaerobes
What are the important species of clostridium?
Clostridium perfringens
Clostridium tetani
Clostridium botulinum
Clostridium difficile
Do spores persist in the environment?
Yes and they are the infective form
What kind of features make clostridium produce disease?
They produce toxins
What are the 5 types of toxins that clostridium perfringens produce?
A B C D E
What are the toxins produced in gas gangrene and food poisoning by clostridium perfringens?
Alpha toxin
What are the toxins produced by enteritis necroticans causing clostridium perfringens?
Alpha and beta toxins
How does gas gangrene occur?
Spores enter into open or traumatic wounds
How does gas gangrene kill?
Clostridium perfringens rapidly invade and liquefy muscle (liquefactive necrosis) and surrounding tissue
Why is it called gas gangrene?
Pathogenic clostridium perfringens produce gas in the tissue they destroy
What type of toxin is produced in gas gangrene?
Alpha toxin
What type of toxin is produced in type A clostridium perfringens?
A very potent enterotoxin is produced during spore formation in small intestine