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Infection > Session 10 - Influenza & Escherichia Coli > Flashcards

Session 10 - Influenza & Escherichia Coli Flashcards

1
Q

What is the structure of influenza virus?

A

Spherical, enveloped viruses containing a segmented, negative strand RNA genome

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2
Q

What are the 2 surface antigens on influenza?

A

Hemagglutinin H

Neuraminidase N

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3
Q

What is the function of haemagglutinin?

A

Binds to cells of the infected person

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4
Q

What is the function of neuraminidase?

A

Releases virus from host cell surface

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5
Q

Why is influenza A the most concerning?

A

Big animal reservoir

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6
Q

How does influenza enter cell?

A

Hemagglutinin protein on influenza virus binds to NANA residue which act as receptor, receptor mediated endocytosis occurs

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7
Q

What route and what are the 3 potential modes of transmission of influenza?

A

Respiratory route

Small particle aerosols - remain suspended in air for many hours
Larger particle or droplets - infect people in direct contact
Land on surfaces

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8
Q

What are 3 barriers of entry of influenza via respiratory route?

A
  1. Respiratory epithelial cells are covered by thick glycocalyx and tracheobronchial mucus that can trap virus particles
  2. Ciliated respiratory epithelial cells continually sweep mucus up from lower respiratory tract into upper
  3. Immunologic defenses in lung - IgA, NK cells and macrophages
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9
Q

How does influenza virus leave cells?

A

Neuraminidase cleaves area between sialic acids and galactose

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10
Q

What are 4 symptoms of influenza?

A

Fever
Dry cough
Nausea
Fatigue

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11
Q

What is the incubation period of influenza?

A

1-5 days

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12
Q

What are 4 groups of people who have a higher risk of complication?

A

Children under 6 months
Older people over 65
People with underlying health conditions
Pregnant women

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13
Q

What are 5 examples of possible complications of influenza?

A 
Febrile convulsions 
Pericarditis
Otitis media
Increased maternal complications
Rhabdomyolysis
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14
Q

How to diagnose influenza?

A

Nasopharyngeal swab, tissue culture, symptoms, clinical assessment

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15
Q

What are 3 treatments for influenza?

A

Antivirals
Neuraminidase inhibitors
Prevention

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16
Q

How do antivirals treat influenza?

A

Antivirals inhibit viral unposting after uptake through M2 protein influenza A

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17
Q

What are 2 examples of antivirals?

A

Rimantadine

Amanda dine

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18
Q

How do neuraminidase inhibitors treat influenza?

A

Inhibit viral release from infected cell and cause aggregation of viral particles for influenza A and B

19
Q

What are 2 examples of neuraminidase inhibitors?

A

Oseltamivir

Zanamivir

20
Q

How to prevent influenza?

A

Formalin-inactivated vaccine by injection for influenza A and B

21
Q

Why are there genetic changes in the influenza virus?

A

Flu virus life cycle is 6h, constantly replicates and have a high error rate, and lack of proofreading ability = mutations

22
Q

What is antigenic drift?

A

Minor changes or natural mutations in genes that occur gradually over time, causing seasonal epidemics - minor antigenic changes in H and N proteins, dye to random mutations in viral RNA

23
Q

What is antigenic shift?

A

Major changes in genes or flu viruses that occur suddenly when 2 or more different strains combine, resulting in new subtype and can cause widespread epidemics or pandemics, due to reassortment of different RNA segments from each species in a new capsid

24
Q

How does reassortment of RNA occur?

A

Influenza type A in many animals, simultaneously infected with multiple subtypes in a single host - mRNAs encoding H and N antigens have been reassorted into unique combinations

25
Q

What is the consequence of antigenic shift?

A

New subtype of influenza virus - no defense against it can cause epidemics and pandemics

26
Q

What are 2 ways flu can actually kill people?

A

Overreaction of immune system, T cells attack and destroy tissues
Opportunistic secondary infection

27
Q

What is the gram stain of E. Coli?

A

Gram negative

28
Q

How to identify E. coli in the laboratory?

A

E. coli can use lactose as energy, producing lactic acid, MacConkey agar contains lactose and a pH indicator that goes red with acid pH

29
Q

Where is E. coli normally located?

A

Large bowel microbiota

30
Q

What are 3 types of infections can E. coli cause?

A

Intestinal infections
Extra intestinal infections
Toxin-mediated disease

31
Q

What are 6 types of diarrhoeagenic E. coli?

A 
Enterotoxigenic
Enteropathogenic
Enteroaggregative
Enteroinvasive
Diffusely adherent 
Shiga toxin producing
32
Q

What does enterotoxigenic E. coli cause?

A

Traveler’s diarrhea

33
Q

How is enterotoxigenic E. coli transmitted?

A

Faeco oral transmission

34
Q

What is the mechanism of action of enterotoxigenic E. coli?

A

Produce 2 toxins, heat stable toxin and heat labile toxin, stimulate lining of intestines and cause them to secrete excessive fluid producing profuse watery diarrhea and abdominal cramping

35
Q

What is the mechanism of action of enteropathogenic E. coli?

A

Insert translocated intimin receptor into enterocyte cell membrane and binds to intimin and hence the cell

36
Q

What does shiga toxin-producing E. coli cause?

A

Haemorrhagic colitis = bloody diarrhea

Haemolytic uraemic syndrome - triad of acute renal failure, uaemolytic anaemia and thrombocytopenia

37
Q

What is the molecular actions of shiga toxin?

A

B subunit bind to Gb3, toxin endocytosed and transported to Golgi apparatus and ER, A chain is cleaved into small A2 and active A1. A1 inactivated ribosomes, inhibit protein synthesis, cell death

38
Q

What are 4 virulence factors of extra-intestinal pathogenic E. coli?

A

Adhesins
Iron acquisition systems
Protectins and invasins
Toxins

39
Q

How do uropathogenic E. coli cause urinary tract infections?

A

Transfer from rectum to urethra and migrate to bladder
type 1 fimbriae have adhesive tips that bind to uroepithelium
alpha haemolysin cytotoxic towards epithelial cells in urinary tract
Siderophores acquire iron

40
Q

What are 3 symptoms of cystitis?

A

Frequent and urgent ruination
Dysuria
Nocturia

41
Q

How to Prevent E. coli?

A

Avoid food and drinks that could be contaminated

42
Q

How to treat E. coli infection?

A

Most will recover within a few days
Clear liquids to prevent dehydration and loss of electrolytes
Oral rehydration solutions
Avoid antibiotics

43
Q

What are 2 commonly used antibiotics for UTI?

A

Trimethoprim

Nitrofurantoin

Infection (11 decks)

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