Microbiology/Immunology Flashcards
What is dysentry? Two main bacterial causes? (include their gram stain and respiration)
Blood and mucus in diarrhoea.
Shigella dysenteriae and enteroinvasive E.coli. Both gram - rods that are facultative anaerobic
What is the most common cause of food borne diarrhoea? Whats it’s mechanism?
Salmonella, uptake via M cells, infects eptithelial cells then invades lamina propria to cause inflammation
What is the most common cause of travellers diarrhoea? What is its mechanism?
ETEC, attaches via fimbriae and release HL and HT enterotoxins
What causes antibiotic associated diarrhoea (pseudomembranous colitis) and how?
What happens in it?
Clostridium difficile, it normally lives in gut and antibiotics inhibit other gut flora allowing it to multiple.
Produces cytotoxic toxins which cause cell death, inflammation and necrosis
What are the two main causes of hemorrhagic colitis? What can it lead to?
EHEC and shigella dysenteriae
Haemorrhagic uremic syndrome
How does EPEC cause diarrhoea?
Adheres initially via plasmid mediation.
Then chromosomal genes produce Bfp, ignition and Tir which allows attachment efacement onto the microvilli to occur, disrupting them.
When do we use antibiotics to treat diarrhoea? Which antibiotic is commonly used?
Protozoa, pseudomembranous colitis, severe shigella, cholera, if gone systemic, immunocompromised patients.
Use metronidazole
What are the 4 main phyla of bacteria that live in the GIT?
Firmicutes
Bacterodetes
Actinobacteria
Proteobacteria
What 2 signals are needed to activated IL-1?
Signal from a TLR to produce Pro-IL-1B
Signal from NLR–>inflammasome that cleaves caspase-1.
Caspase-1 then cleaves to create active IL-1
How do macrophages release IL-1? What are some of IL-1’s functions once released?
By undergoing pyroptosis (dying therefore releasing it)
- neutrophil activation which clear up pathogen
- fever
- B and T cell activation
How do inflammasomes contribute to metabolic syndrome?
Obesity is low grad inflamm disease as adipocytes die.
Causes inflammasome activation
IL-1 causes insulin resistance, which in long term can cause death of liver and pancreatic cells (eventual type 2 diabetes)
Where are M cells located and what do they do?
Located in epithelium above Peyers patches in SI.
Deliver antigens to the APC in the PP.
How do we home activated T and B cells back to the mucosa?
Dendritic cells induce addressin a4B7 which binds to integrin MAdCAM1 on mucosal epithelial cells
Which antibody do B cells committee to produce in the SI and why?
IgA as it neutralises gut pathogens and their toxins
What are the direct and indirect effects of the microbiota on the gut immune system?
Direct: Blocks binding sites and produces bacteriocins
Indirect: Cause PAMP signalling which:
- Production of mucus
- Proliferation of crypt enterocytes: Antimicrobials and immunomodulators
- PAMPs on IEL, LTi and NK-22 cause IL-22 release which is involved in epithelial integrity and antimicrobial defence
- The short chain fatty acids cause inactivation of Nf-KB
What T cells does the microflora produce vs pathogens?
DC PRR activated by microbiota induce tolerogenic T cells- TH2 and Treg (physiological inflammation)
DC PRR activated by pathogens induce inflammatory T cells- TH1 and TH17 (pathologenic inflammation)
What does obesity do to gut microbiota diversity and wha are the consequences of this?
It decreases diversity
- Means more insulin resistant
- More serum triglycerides
- Higher cholesterol
What is the pathogenesis of hepatitis from?
The immune response
What family does Hep A belong to? Acute/chronic What +/-, ss/ds, DNA/RNA, enveloped Site of primary replication Where do they come from and what is their route of transmission?
Picornaviridae Acute \+ ss RNA Non enveloped Liver From faeces and transmit via faecal-oral route
What family does Hep E belong to? Acute/chronic What +/-, ss/ds, DNA/RNA, enveloped Site of primary replication Where do they come from and what is their route of transmission?
Hepeviridae Acute \+ ssRNA Non enveloped They dont know From faeces and transmit via faecal-oral route
What does +IgM and +IgM vs +IgM and -IgM mean in terms of Hep A/E infection?
If IgG and IgM + then in the middle of acute hepatitis
If IgM- then are a while past the acute infection and are immune or have been vaccinated (in case of hep A)
What does HBeAg and Anti–Hbe Ig represent?
HBeAg shows He B virus is replicating in liver.
Anti-Hbe Ig shows no longer replicating, goal of treatment.
What are some Hep B antivirals?
IFNa and nucleotide analogues
In reference to Hep B is it: Acute/chronic What +/-, ss/ds, DNA/RNA, enveloped Site of primary replication Where do they come from?
Chronic ds DNA (incomplete) Outer envelope and inner nucleocapsid core Liver Route via blood/body fluids
