MICROBIOLOGY

Question 1

What is the normal range for WCC?

Answer 1

4 - 11 x 109/L

Question 2

What is the normal range for neutrophils?

Answer 2

2.0 – 7.0 x 109/L

Question 3

When CRP (C-reative protein) is raised this indicates infection.

Answer 3

It is released into the body from the liver in response to inflammation

Question 4

ESR (erythrocyte sedimentation rate) is used to detect inflammation in the body.

Answer 4

An ESR test can monitor inflammatory conditions, such as rheumatoid arthritis or systemic lupus erythematosus

Question 5

What is an MSU?

Answer 5

midstream specimen of urine

Used to detect infection

Question 6

What kind of antitbiotic is Gentamicin and what is its mechanism of action?

Answer 6

Aminoglycoside

Bind irreversibly to the 30S subunit of bacterial ribosomes and inhibit protein synthesis

Question 7

What are ahminoglycosides active against?

Answer 7

Gram negative, anaerobic bacteria, staphylococci and mycobacteria

Question 8

Aminoglycosides can impair neuromuscular transmission so should not be given to people with m_______ g______

Answer 8

Myasthenia Gravis

Question 9

Ototoxicity caused by ahminoglycosides can be enhanced if co-prescribed with other drugs causing this such as ?

Answer 9

Loop diuretics- furosemide

Vancomycin

Question 10

Vancomycin is a glycopeptide used to treat mainly gram ______ bacteria such as Endocarditis/ MRSA.

Answer 10

Gram POSITIVE

Aerobic and anaerobic gram positive bacteria

(gent= negative, vanc= positive)

Question 11

What antibiotics do we use in the treatment of C.diff?

Answer 11

Metronidazole first line

Vancomycin oral second line

Question 12

What is Vancomycins mechanism of action?

Answer 12

Its a GLYCOPEPTIDE
It inhibits growth and cross-linking of peptidoglycan chains- inhibiting the cell wall synthesis in gram positive bacteria.

It is inactive against gram negative bacteria which have a difference cell wall structure containing lipopolysaccharides

Note: Teicoplanin is also a glycopeptide that has a spectrum of activity and mechanism very similar to vanc

Question 13

What can happen if vancomycin is infused too rapidly?

Answer 13

RED MAN SYNDROME
Erythema, hypotension, bronchospasm

vancomycin must therefore be given as a slow IV infusion (NOT IV bolus or IM Injection) infuse over at least 60 minutes

Question 14

What do we commonly see prescribed for CAP?

Answer 14

Amoxicillin 1g TDS + Clarithromycin 500mg BD

Can add in Vancomycin third line

Question 15

What do we commonly see prescribed for HAP?

Answer 15

Amoxicillin 1g TDS + Gentamicin (for pseudomonas cover/ gram negative)

Stepdown to co-amoxiclav

Question 16

Metronidazole is commonly used to treat anaerobic bacterial infections such as?

Answer 16

oral infections (dental abscess)
Tonsillitis/ quinsy 
aspiration pneumonia
C.diff
Gyneacologic infections: Pelvic Inflammatory disease

All the above involve ANAEROBIC bacteria

Question 17

What is metronidazole mechanism of action?

Answer 17

It works in anaerobic bacteria. It is reduced inside the bacterial cell to form a toxic free radical that binds to DNA and reduces DNA synthesis.

Question 18

Is metronidazole hepatically or renally cleared?

Answer 18

Hepatically

It should therefore not be used in people with severe liver disease

Question 19

Why are anearobic bacteria often resistant to pencillins?

Answer 19

Due to the production of beta-lactamases

Question 20

What does metronidazole interact with?

Answer 20

Warfarin (reduces metabolism through inhibiting CYP450)
Phenytoin
Rifampicin
lithium

Question 21

What is Teicoplanins mechanism of action?

Answer 21

Same as vancomycin- it inhibits cross-linkage of peptidoglycan chains in bacterial cell walls and therefore inhibits their synthesis. Active against gram POSITIVE bacteria.

It is bacteriocidal- (cell wall- house analogy)

Question 22

What is the basic mechanism of action of all penicillins?

Answer 22

Inhibit enzymes responsible for cross-linking peptidoglycan in bacterial cell walls- this weakens cell walls- water then enters, cells swell, burst and die

Question 23

What structure do penicillins contain which is responsible for their activity?

Answer 23

A beta-lactam ring

But this is what causes resistance: bacteria can produce beta-lactamase enzymes which break this ring apart :(

Question 24

When does the rash usually show up in those with a penicillin allergy following penicillin exposure?

Answer 24

7- 10 days after first exposure

1-2 days after repeat exposure

Question 25

What do penicillins interact with?

Answer 25

Methotrexate- they reduce renal excretion of methotrexate leading to toxicity

Question 26

Benzylpenicillin/ penicillin V are usually used for the treatment of tonsillitis/ quinsy. What dose?

Answer 26

Benzypenicillin (IV ONLY)- 1.2g QDS Penicillin V (phenoxymethylpeniciilin) 500mg -1g QDS

Question 27

Tazocin is an antipseudomonal penicillin. It is reserved for severe infections. It covers pseudomonas aeruginosa. What is it that makes this antibiotic active against Beta lactamase-producing bacteria?

Answer 27

The addition of the beta lactamase INHIBITOR tazobactam- makes it active again things like staph aureus It should be used with caution in those at risk of C.diff Reduce dose in moderate/ severe renal impairment

Question 28

What penicillins do we use for the empirical treatment of pneumonia as they have broad spectrum of activity again gram positive and gram negative bacteria?

Answer 28

Amoxicillin Co-amoxiclav (Co-amoxiclav is just amoxicillin with the addition of clavulanic acid- a beta-lactamase inhibitor).

Question 29

Broad spectrum antibiotics such as co-amoxiclav, amoxivillin, tazocin should be used with caution in those at risk of what?

Answer 29

C.diff | as they can wipe out gut flora an cause c.diff in these patients e.g. elderly

Question 30

Broad spectrum antibiotics such as amoxicillin and co-amoxiclav can increase the anticoagulant effects of warfarin. How?

Answer 30

By killing normal gut flora that synthesise vitamin K

Question 31

Flucloxacillin is contraindicated in patients with prior flucloxacillin-related hepatotoxicity

Answer 31

Short half life (45 mins) therefor QDS administration

Question 32

Teicoplanin needs dose adjustment in renal impairment

Answer 32

Use normal dose regimen on days 1–4, then use normal maintenance dose every 48 hours if eGFR 30–80 mL/minute/1.73 m2 Use normal maintenance dose every 72 hours if eGFR less than 30 mL/minute/1.73 m2.

Question 33

What antibiotic can we use for skin infections if the patient has a penicillin allergy?

Answer 33

Clarithromycin- a macrolide

Question 34

We use clarithromycin in chest infections such as pneumonia, alongside amoxicillin. What does clarithromycin cover for?

Answer 34

Atypical cover | e.g. Legionella and Mycoplasma pneuoniae

Question 35

What is the triple therapy for H.pylori?

Answer 35

Clarithromycin (macrolide) + Amoxicillin or Metronidazole + PPI

Question 36

What is the mechanism of Macrolides such as clarithromycin, azithromycin and erythromycin?

Answer 36

Bind to the 50S subunit of bacterial ribosomes and inhibit bacterial protein synthesis They are bacteriostatic (i.e stop growth)

Question 37

What do macrolides such as clarithromycin, erythromycin PROLONG? What drugs do we therefore need to watch out for?

Answer 37

Prolong the QT INTERVAL Watch out for drugs that also prolong QT interval or cause arrythmias such as amiodarone, antipsychotics, quinine, quinolone (moxifloxacin, ciprofloxacin)

Question 38

What is the mechanism of action of cephalosporins such as ceftriaxone, cefalexin, cefotaxime?

Answer 38

Inhibit enzymes responsible for cross-linking peptidoglycan in bacterial cell walls- this weakens cell walls- water then enters, cells swell, burst and die Same as that of penicillins and meropenem NB: Cephaolsporins and meropenem are naturally more resistant to B-lactamases than penicillins are therefore they are reserved for very severe or complicated infections caused by antibiotic-resistant organisms

Question 39

If meropenem is prescribed in those with renal impairment or in too higher doses, what do we put the patient at risk of?

Answer 39

CNS toxicity including seizures Should be used with caution in patients with epilepsy Meropenem will also reduce plasma concentration of sodium valproate

Question 40

What antibiotics do we usually use for treatment of meningitis?

Answer 40

Cephalosporins- Ceftriaxone or Cefotaxime IV If patient has a penicillin allergy use Chloramphenicol

Question 41

What is the mechanism of action of QUINOLONES (ciprofloxacin, moxifloxacin, levofloxacin)?

Answer 41

Inhibit DNA synthesis Particularly active against gram negative bacteria but moxifloxacin and levofloxacin have developed activity against gram positive also.

Question 42

What are the use of Quinolones (ciprofloxacin, moxifloxacin, levofloxacin) cautioned in?

Answer 42

They can lower seizure threshold so caution in EPILEPSY Co-prescription of NSAID's and quinolones increases seizure risk QT PROLONGATION Myasthenia graves

Question 43

Quinolones (ciprofloxacin, moxifloxacin, levofloxacin) can produce some nasty side effects, such as?

Answer 43

Lower seizure threshold Hallucination Rupture of muscle tendons QT interval prolongation

Question 44

Why is trimethoprim contra-indicated in Pregnancy for UTI's? What do we use instead?

Answer 44

It is a folate antagonist so it teratogenic in the first trimester We should use Cefalexin for UTI's in pregnancy

Question 45

What is the rare but very serious side effect of penicillins that can occur due to cerebral irritation?

Answer 45

Encephalopathy Should never be given intrathecally (into spine)

Question 46

What can co-amoxiclav and flucloxacillin cause up to 2 months after use and as a result these need to be used with caution in patient with LIVER dysfunction?

Answer 46

CHOLESTATIC JAUNDICE