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
What are the symptoms of clostridium perfringens in GI tract?
Crampy abdominal pain
Diarrhoea
Self limiting
What causes Necrotising bowel disease?
Ingestion of contaminated food with food rich in trypsin inhibitors
What causes damage during necrotising bowel disease?
Necrosis of bowel or bowel segment caused by beta toxin not being broken down due to trypsin inhibition
What is another name for necrotising bowel disease?
Pig bel
Why is necrotising bowel disease also called pig bel?
People in papua new ginea ate pig meat that wasn’t completely cooked with clostridium perfringens spores in them as well as sweet potatoes causing that disease
What type of disease is enteritis necroticans?
Type C
Where are clostridium tetani spores typically found?
Spores found in the soil
How does tetanus get into the body?
through wounds and then they germinate
How do clostridium tetani cause disease?
they produce a powerful neurotoxin called tetanospasmin
What does tetanus do?
Blocks inhibitory nerve impulses
Is tetanus a problem today?
In developing countries it is very deadly but in developed countries it is very rare due to vaccination
What are symptoms of tetanus?
Increased muscle tone and painful spasms
Trismus (lockjaw)
Risus sardonicus
Abdominal rigidity
Apnoea
Autonomic NS instability
Sweating
cardiac arrhythmias
labile BP
high fatality
What does clostridium botulinum do?
produces neurotoxin that causes paralysis preventing release of acetylcholine at neuromuscular junction causing progressive descending paralysis
How does clostridium botulinum enter the body?
enters in food or wound contamination
What food can potentially contain clostridium botulinum?
aged or preserved foods
Where can clostridium difficile found?
In faeces of 30% of hospital patients
Spores persist in environment and spread on hands of staff
What kind of toxin can clostridium difficile produce and what type of disease does it cause?
It produces enterotoxins and antibiotic associated diarrhoea (during or after antibiotic treatment)
This is due to death of competitive microbiota
How severe is the diarrhoea associated with clostridium difficile?
Mild to severe and intractable
What does clostridium difficile associated diarrhoea cause in its most severe cases?
Pseudomembranous colitis which is a severe inflammatory condition
What are lactobacillus like in terms of oxygen use and endospore formation?
Lactobacillus can be aerobic or anaerobic and are regular non-endospore producing bacteria
What is the normal role of lactobacillus species?
They are part of the normal flora of the GIT and vagina.
They ferment carbohydrates to lactic acid and maintain vaginal pH at 3.8 - 4.5
What is the oxygen usage and endospore formation of listeria like?
They are aerobic and non-endospore forming
Where can listeria be found?
Water
Animal and human faeces
Raw meat
Dairy products
Vegetables
What temperature can listeria grow at that is clinically significant?
4 degrees
What are some high risk foods associated with listeria?
coleslaw, raw cabbage
Unpasteurised milk
Soft cheeses
Pate
Undercooked chicken
Prepacked sliced meals
Is listeria infection common?
no but causes serious infections
Who typically has issues with listeria and who doesn’t?
It creates no symptoms in people with normal individuals.
Elderly, infants, immunocompromised, and pregnant people typically have issues with listeriosis.
Fetal infection can occur if mother is infected.
What are the symptoms of listeriosis?
Non-specific bacteraemia - flu like symptoms
Septicaemia +/- meningitis
What does infection of listeria do to pregnant people?
miscarriage, stillbirth, prem labour
Live birth - septicaemia, meningitis, and neurological damage
What is the oxygen usage and endospore formation like in erysipelothrix rhusiopathiae?
It is aerobic and non-endospore forming
How does erysipelothrix enter the body?
Through skin abrasions caused by handling meat, poultry, fish, crustaceans, and farm animals
What does infection of erysipelothrix look like?
Painful, raised areas of inflammation of the skin
What can be said about corynebacterium’s oxygen usage and endospore formation and morphology?
They are aerobic and non-endospore forming.
They are irregular with what is described as coryneform or diptheroid morphology
Where are corynebacterium found?
Many are commensals of humans and animals
Are corynebacterium common infections?
No they are often associated with other things like foreign devices
What is the major pathogen of the corynebacterium genus?
Corynebacterium diphtheriae
What disease is caused by corynebacterium diphetheriae?
diphtheria
What demographic is typically affected by diphtheria?
Children without vaccinations
What happens during diphtheria?
Exotoxin produced which infects nose and throat which ulcerate and swell.
The swelling can cause asphyxiation.
What are the symptoms of diphtheria?
Skin ulcers
Inflammation, swelling and pseudomembrane formation in nasopharynx and upper airways
What happens when the exotoxin produced by corynebacterium diphtheria is absorbed into the body?
A severe pathology causing:
Myocarditis (damage to heart muscle) arrhythmias and heart failure
Neuropathy with paralysis of palate muscles and cranial nerves as well as peripheral sensory and motor neuropathy.
Other sites of damage include focal necrosis in the kidneys, adrenals, and liver
When was the first diphtheria vaccine introduced?
1932
What is the oxygen usage and spore formation of propionibacterium like?
Anaerobes that do not produce spores
What is propionibacterium morphology like?
irregular coryneform morphology
Where are propionibacterium typically found?
Commensals on human skin and they are non pathogenic which typically contaminate blood cultures and P.acnes have a role in acne vulgaris
Where can propionibacterium cause infections?
Implanted foreign devices
What are some aerobic nonendospore forming actinomycetes?
Nocardia
Actinomadura
Streptomyces
What are actinomycetes?
filamentous and branching structure
What is aerobic capacity of actinomycetes?
Can be both aerobic and anaerobic
Where are actinomycetes typically found?
Soil and rotting vegetation
What do actinomycetes look like on agar plates?
like fungi
What are some diseases caused by actinomycetes?
Actinomycotic mycetomas which look like eumycotic mycetoma
Other nocardia infections
Actinomycosis
What are the most common actinomycotic genera that cause disease?
Nocardia
Actinomadura
Streptomyces
How do actinomyces enter the skin?
Through cutaneous implantation such as through a stick, thorn, or splinter
What kind of infection do actinomyces cause?
Chronic lesion that takes years to develop resulting in swelling, dischargind sinuses and granules
Where is nocardia typically seen?
Immunocompromised hosts
How does nocardia cause infection?
it enters through inhalation as a respiratory infection and forms nodules in the lungs as well as pneumonia and cavities.
It abscesses in organs
How does nocardia spread?
Through blood
What does nocardia do in immunocompetent patients?
Skin implantation
Nodular/pus-filled lesions tracking up lymphatics
Very similar to fungal infection called “sporotrichoid”
Where are actinomyces species typically found?
Commensal bacteria of oropharynx, GIT, and genital tract
What are the forms of actinomycete disease?
Cervicofacial
Thoracic
Abdomen, pelvis (associated with long standing intrauterine devices)
What are the symptoms of cervicofacial actinomycosis?
Swelling
Contiguous spread
Discharging fistulas
Pus containing granules
