Session 10 - Influenza & Escherichia Coli

Question 1

What is the structure of influenza virus?

Answer 1

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

Question 2

What are the 2 surface antigens on influenza?

Answer 2

Hemagglutinin H

Neuraminidase N

Question 3

What is the function of haemagglutinin?

Answer 3

Binds to cells of the infected person

Question 4

What is the function of neuraminidase?

Answer 4

Releases virus from host cell surface

Question 5

Why is influenza A the most concerning?

Answer 5

Big animal reservoir

Question 6

How does influenza enter cell?

Answer 6

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

Question 7

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

Answer 7

Respiratory route

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

Question 8

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

Answer 8

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

Question 9

How does influenza virus leave cells?

Answer 9

Neuraminidase cleaves area between sialic acids and galactose

Question 10

What are 4 symptoms of influenza?

Answer 10

Fever
Dry cough
Nausea
Fatigue

Question 11

What is the incubation period of influenza?

Answer 11

1-5 days

Question 12

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

Answer 12

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

Question 13

What are 5 examples of possible complications of influenza?

Answer 13

Febrile convulsions 
Pericarditis
Otitis media
Increased maternal complications
Rhabdomyolysis

Question 14

How to diagnose influenza?

Answer 14

Nasopharyngeal swab, tissue culture, symptoms, clinical assessment

Question 15

What are 3 treatments for influenza?

Answer 15

Antivirals
Neuraminidase inhibitors
Prevention

Question 16

How do antivirals treat influenza?

Answer 16

Antivirals inhibit viral unposting after uptake through M2 protein influenza A

Question 17

What are 2 examples of antivirals?

Answer 17

Rimantadine

Amanda dine

Question 18

How do neuraminidase inhibitors treat influenza?

Answer 18

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

Question 19

What are 2 examples of neuraminidase inhibitors?

Answer 19

Oseltamivir

Zanamivir

Question 20

How to prevent influenza?

Answer 20

Formalin-inactivated vaccine by injection for influenza A and B

Question 21

Why are there genetic changes in the influenza virus?

Answer 21

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

Question 22

What is antigenic drift?

Answer 22

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

Question 23

What is antigenic shift?

Answer 23

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

Question 24

How does reassortment of RNA occur?

Answer 24

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

Question 25

What is the consequence of antigenic shift?

Answer 25

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

Question 26

What are 2 ways flu can actually kill people?

Answer 26

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

Question 27

What is the gram stain of E. Coli?

Answer 27

Gram negative

Question 28

How to identify E. coli in the laboratory?

Answer 28

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

Question 29

Where is E. coli normally located?

Answer 29

Large bowel microbiota

Question 30

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

Answer 30

Intestinal infections Extra intestinal infections Toxin-mediated disease

Question 31

What are 6 types of diarrhoeagenic E. coli?

Answer 31

``` Enterotoxigenic Enteropathogenic Enteroaggregative Enteroinvasive Diffusely adherent Shiga toxin producing ```

Question 32

What does enterotoxigenic E. coli cause?

Answer 32

Traveler’s diarrhea

Question 33

How is enterotoxigenic E. coli transmitted?

Answer 33

Faeco oral transmission

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

What does shiga toxin-producing E. coli cause?

Answer 36

Haemorrhagic colitis = bloody diarrhea | Haemolytic uraemic syndrome - triad of acute renal failure, uaemolytic anaemia and thrombocytopenia

Question 37

What is the molecular actions of shiga toxin?

Answer 37

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

Question 38

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

Answer 38

Adhesins Iron acquisition systems Protectins and invasins Toxins

Question 39

How do uropathogenic E. coli cause urinary tract infections?

Answer 39

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

Question 40

What are 3 symptoms of cystitis?

Answer 40

Frequent and urgent ruination Dysuria Nocturia

Question 41

How to Prevent E. coli?

Answer 41

Avoid food and drinks that could be contaminated

Question 42

How to treat E. coli infection?

Answer 42

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

Question 43

What are 2 commonly used antibiotics for UTI?

Answer 43

Trimethoprim | Nitrofurantoin