Microbiology 3 Flashcards by Amy Spicer

Which organisms are Gram +ve?

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

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How is C.Diff treated?

Metronidazole
Vancomycin

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What are the Sx of tetanus?

Autonomic overactivity
Spasms of voluntary muscles

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Do you need a vaccination against tetanus?

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

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Which organisms are gram -ve?

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

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

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

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Which type of E.Coli is the most severe?

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

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

Form biofilm over urothelial cells

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How does Klebsiella acquire resistance?

Through plasmids
Particularly seen in gram -ve bacteria

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How helpful are leukocytes/nitrites on a urine dipstick?

Nitrite: High specificity
Leukocytes: Low specificity, high sensitivity

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How is H.Pylori treated?

PPI, 2 antibiotics (amoxicillin & Macrolide)

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What are the Sx of Typhoid?

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

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How is Typhoid treated?

Fluoroquinolones
Vaccination 30-70% effective

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Where does Shigella affect?

Large bowel
Invades colonic epithelial cells
Causes bloody diarrhoea

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How is Campylobacter treated?

Clarithromycin

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What is a complication of Campylobacter?

Guillan-Barre Syndrome

What is the triad of reactive arthritis?

Arthritis
Conjunctivitis
Urethritis

What are the causes of reactive arthritis?

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

What are the other Sx of reactive arthritis?

Iritis
Circular balanitis
Keratoderma blenorrhagia

How long does immunity to Norovirus last?

4-10/52

How is gonorrhoea treated?

IM Ceftriaxone
Plus Azithromycin

What are the complications of gonorrhoea?

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

What is the complication of chronic Chlamydia in women?

Half of asymptomatic women progress to PID

What are the Sx of Chlamydia in men?

Discharge
Urethritis

How is Chlamydia diagnosed?

NAATs

How is Chlamydia treated?

Doxycycline

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

- 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

What are the 3 mechanisms of action of antibacterials?

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

How do B-Lactams work?

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

How do Glycopeptides act as antibacterials?

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

How to antibacterials that inhibit protein synthesis generally work?

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

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

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

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

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