Microbiology 3

Question 1

Which organisms are Gram +ve?

Answer 1

BACILLI: Clostridium, Bacillus, Listeria, Coryne
COCCI: Staph, Strep

Question 2

How is C.Diff treated?

Answer 2

Metronidazole
Vancomycin

Question 3

What are the Sx of tetanus?

Answer 3

Autonomic overactivity
Spasms of voluntary muscles

Question 4

Do you need a vaccination against tetanus?

Answer 4

5 childhood vaccines should give life-long immunity
If infected & showing Sx need immunoglobulins

Question 5

Which organisms are gram -ve?

Answer 5

• ENTEROBACTERIA: E.Coli, Klebsiella, Salmonella, Shigella, Proteus
  -Pseudomonas
  -Neisseria
• Haemophilus
• Legionella
• H.Pylori
• Campylobacter
• Gonorrhoe

Question 6

What’s the difference between gram +ve & Gram -ve?

Answer 6

Thick peptidoglycan layer in gram +ve cells wall which takes up staining
Gram -ve has lipopolysaccharide layer outside of this so staining can’t reach

Question 7

Which type of E.Coli is the most severe?

Answer 7

E.Coli Verotoxin (0157)
Through contaminated food
10% causes HUS

Question 8

Why is E.Coli UTI difficult to get rid of?

Answer 8

Form biofilm over urothelial cells

Question 9

How does Klebsiella acquire resistance?

Answer 9

Through plasmids
Particularly seen in gram -ve bacteria

Question 10

How helpful are leukocytes/nitrites on a urine dipstick?

Answer 10

Nitrite: High specificity
Leukocytes: Low specificity, high sensitivity

Question 11

How is H.Pylori treated?

Answer 11

PPI, 2 antibiotics (amoxicillin & Macrolide)

Question 12

What are the Sx of Typhoid?

Answer 12

High fever
Cough
Abdominal pain
Relative bradycardia
Rose spots in pale skin
3rd week: Necrosis of Peyer’s patches & peritonitis

Question 13

How is Typhoid treated?

Answer 13

Fluoroquinolones
Vaccination 30-70% effective

Question 14

Where does Shigella affect?

Answer 14

Large bowel
Invades colonic epithelial cells
Causes bloody diarrhoea

Question 15

How is Campylobacter treated?

Answer 15

Clarithromycin

Question 16

What is a complication of Campylobacter?

Answer 16

Guillan-Barre Syndrome

Question 17

What is the triad of reactive arthritis?

Answer 17

Arthritis
Conjunctivitis
Urethritis

Question 18

What are the causes of reactive arthritis?

Answer 18

Diarrhoea: Salmonella, Campylobacter, Shigella
STD: Chlamydia, Gonorrhoea

Question 19

What are the other Sx of reactive arthritis?

Answer 19

Iritis
Circular balanitis
Keratoderma blenorrhagia

Question 20

How long does immunity to Norovirus last?

Answer 20

4-10/52

Question 21

How is gonorrhoea treated?

Answer 21

IM Ceftriaxone
Plus Azithromycin

Question 22

What are the complications of gonorrhoea?

Answer 22

Chronic (men = strictures, women = PID)
Septic arthritis
Epididymo-orchitis
Bacterial endocarditis
Reactive arthritis

Question 23

What is the complication of chronic Chlamydia in women?

Answer 23

Half of asymptomatic women progress to PID

Question 24

What are the Sx of Chlamydia in men?

Answer 24

Discharge
Urethritis

Question 25

How is Chlamydia diagnosed?

Answer 25

NAATs

Question 26

How is Chlamydia treated?

Answer 26

Doxycycline

Question 27

What is the difference between aerobic, anaerobic & facultative anaerobic bacteria?

Answer 27

• Aerobic: Use O2 for metabolism, can only survive if O2 present but needs enzymes to detoxify O2
  -Anaerobic: Metabolise without O2, Cannot survive in presence of O2
• Facultative: Can survive with/without O2 but prefer with

Question 28

What are the 3 mechanisms of action of antibacterials?

Answer 28

1) Action on cell wall synthesis: B-lactams, Glycopeptides
2) Inhibition of protein synthesis: Tetracyclines, Aminoglycosides, Macrolides, Chloramphenicol
3) Inhibition of nucleic acid synthesis: Metro, Rifampicin, Trimethoprim

Question 29

How do B-Lactams work?

Answer 29

1) Rely on integrity of B-lactam ring
2) Bind to & inhibit enzymes that catalyse link preventing cross-bridges between peptidoglycan polymer chains
Examples: Penicillins, Ceph, carbapenems

Question 30

How do Glycopeptides act as antibacterials?

Answer 30

Interfere with cell wall synthesis by binding to peptidoglycan chains preventing formation of cross-links
Examples: Vanc, Teic

Question 31

How to antibacterials that inhibit protein synthesis generally work?

Answer 31

Selectively toxic
Tend to be bacteriostatic
Bacterial ribosomes consist of 50S & 30S subunit

Question 32

How do Macrolides, Tetracyclines, Aminoglycosides, Clindamycin & Chloramphenicol work?

Answer 32

M: Bind to 50S subunit inhibiting peptide chain translocation
T: Bind to 30S subunit & inhibit binding of aminoacyl-tRNA
A: Same as tetracyclines but cause misreading of mRNA
Cl: Disrupt function of 50S subunit inhibiting bacterial protein synthesis
Ch: Inhibit peptidyl transferase activity of 50S subunit stopping transpeptidation

Question 33

How does Trimethoprim, Quinolones, Metro, Rifampicin inhibit nucleic acid synthesis?

Answer 33

T: Inhibitor of dihydrofolate reductase needed for purine synthesis
Q: Inhibit DNA gyros (compresses DNA into coils)
M: Inhibits & damages DNA synthesis
R: Prevents RNA transcription by inhibiting DNA dependent RNA polymerase