Week 15 Flashcards
What part of the body to enteric pathogens affect?
Intestine
What are the three main causes of diarrheal diseases?
- toxin in food
- bacteria colonises the gut then makes toxin
- bacteria colonises the gut but doesn’t make toxin
What are the two types of bacterial toxin?
Heat and acid stable
Heat and acid labile (affected)
Describe heat labile botulinum toxin
large gram +ve, anaerobes, sporulating, and come from soil and untreated H2O
Where does food bourne botulism come from?
improperly canned food/ preserves may not show signs of spoilage
What do the symptoms look like for food bourne botulism?
1-2 days after ingestion, nausea and vomitting, then motor loss and possibily death (5-10% cases)
What is Infant botulism?
Food bourne botulism in honey affecting infants under a year old
What is the mechanism for action for Botulinum neurotoxins?
- in GI tract, the toxin affects nerve terminations
- Toxin is taken into the presynaptic node
- Acetylcholine isn’t released into cleft
- Smooth muscle cannot contract
- causes paralysis
What are some other uses of Botulinum?
Overactive bladder/ urine incontinence
Botox
Chronic migraines
Give an example of a bacteria that infects the GI and is enhanced by toxin secretion
E.coli
What antibiotic might be used to treat a bacteria that infects the GI and is enhanced by toxin secretion?
ciprofloxacin
Why might use of antibiotic cause deterioration of the patient infected by a bacteria that infects the GI and is enhanced by toxin secretion?
bacterial death will cause toxin to be released eg. EHEC serotype and shiga toxin
What is the mechanism for action for enterogenic e.coli (ETEC)?
- ETEC enters GI and 37*c causes ETEC to release toxins
- enterotoxins activate cAMP and cGMP second messengers
- This activates cellular kinases
- Controls sodium and chloride channels in intestinal epithelium cells
- Promotes efflux of salt/ water into GI tract
Give an example on bacteria that colonises gut and doesn’t release toxins
Salmonella enterica
What gram is salmonella enterica?
gram -ve
Where is the otitismedia?
Middle ear
Where does the respiratory tract start and end?
Nose to alveoli
What bacteria causes whooping cough?
Bordetella pertusis
What gram is Bordetella pertusis?
-ve
What does fomite mean?
Droplet on surface and bacteria survives
Where does Bordetella pertusis colonise?
Cilia of human respiratory epithelia
What are the two main stages associated with Bordetella pertusis?
Colonisation
Toxemic stage
What 2 things does the colonisation of Bordetella pertusis involve?
Filamentous haemagglutinin
Pertussis toxin
What are the 3 mechanisms of the pertussis toxins?
-Tracheal cytotoxin (stops ciliary beat)
-Lethal toxin
-Invasive adenylate cyclase (disrupts Ca2+ and 2nd messaging)
What pH does skin have?
pH 3-5
What is folliculitis also known as?
a pimple
What is a Furuncle also known as?
a boil
What is a carbuncle also known as?
puss filled abcess
What is erysipelas? and what does it look like?
superficial cellulitis that can spread to the lymph system
red cheeks
What bacteria causes cellulitis?
Streptococcyl
s.aureus
What happens with necrotising fascilitis?
Skin dies
They scrape the dying skin
Which bacteria can spread from a gum infection straight to the heart muscle?
s. aureus
Which bacteria causes ‘honeymoon cystitis’?
s. saphrophyticus
What is the most common fungal skin infection? Where does it like to live?
Candida (some opportunistic like c. albicans)
moist areas eg. armpits and groin
What shape are the yeast cells in c.albicans?
sphere
What form does c.albicans take when it becomes virulent pathogenic? What does it produce?
Hyphae
Produces candidalysin toxin
What does interdigital candidosis look like?
White plaque between fingers
What does oral candidosis look like?
a) red roof of the moth in people with dentures
b) pseudomembrenous in HIV patient, white plaques all over mouth,teeth, gums
What virus causes chickenpox?
Varicella zoster
What virus causes hand, foot and mouth disease?
coxsackievirus
Why is Toxic shock syndrome Tsst-1 referred to as a superantigen?
- MHC class II antigen binds to T receptor on T cells
- the binding is not as selective so many more cells are bound
What three mechanisms allow s.aureus to be a nutrient scavanger?
- alpha, delta= pore forming toxins
- sphingomyelinase binds cholesterol
- gamma= luekocidin lyses leukocytes
What toxin causes scalded skin syndrome?
Exfoliative toxin A
What is the mechanism for Exfoliative toxin A?
Breaks down desmoglein, cutting cell to cell connections, causing skin to flake off
What does PVL stand for? how does it work?
Panton valentine leukocidin
Made by s.aureus, lyses leukocyctes and activates platelets causing thrombosis
What toxin is made by strep. pneumoniae?
Pneumolysin
(pore forming toxin, needed for toxin to adhere, but not too much as otherwise will kill host)
What are these examples of?
Aflatoxin
Gliotoxin
Ochratoxin
Fumonisin
fungal toxins
Mycotoxins
Not essential for bacterial growth, but beneficicial. Not beneficial to human health
What shape are tuberculosis?
Straight or curved rods
What is unique about the myobacterium tuberculosis (MTB) cell wall?
Lipid rich meaning it doesn’t stain well
