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DIPLOMA > MICROBIOLOGY > Flashcards

MICROBIOLOGY Flashcards

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1
Q

What is the normal range for WCC?

A

4 - 11 x 109/L

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2
Q

What is the normal range for neutrophils?

A

2.0 – 7.0 x 109/L

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3
Q

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

A

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

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4
Q

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

A

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

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5
Q

What is an MSU?

A

midstream specimen of urine

Used to detect infection

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6
Q

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

A

Aminoglycoside

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

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7
Q

What are ahminoglycosides active against?

A

Gram negative, anaerobic bacteria, staphylococci and mycobacteria

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8
Q

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

A

Myasthenia Gravis

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9
Q

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

A

Loop diuretics- furosemide

Vancomycin

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10
Q

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

A

Gram POSITIVE

Aerobic and anaerobic gram positive bacteria

(gent= negative, vanc= positive)

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11
Q

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

A

Metronidazole first line

Vancomycin oral second line

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12
Q

What is Vancomycins mechanism of action?

A

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

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13
Q

What can happen if vancomycin is infused too rapidly?

A

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

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14
Q

What do we commonly see prescribed for CAP?

A

Amoxicillin 1g TDS + Clarithromycin 500mg BD

Can add in Vancomycin third line

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15
Q

What do we commonly see prescribed for HAP?

A

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

Stepdown to co-amoxiclav

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16
Q

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

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

All the above involve ANAEROBIC bacteria

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17
Q

What is metronidazole mechanism of action?

A

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.

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18
Q

Is metronidazole hepatically or renally cleared?

A

Hepatically

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

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19
Q

Why are anearobic bacteria often resistant to pencillins?

A

Due to the production of beta-lactamases

20
Q

What does metronidazole interact with?

A

Warfarin (reduces metabolism through inhibiting CYP450)
Phenytoin
Rifampicin
lithium

21
Q

What is Teicoplanins mechanism of action?

A

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)

22
Q

What is the basic mechanism of action of all penicillins?

A

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

23
Q

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

A

A beta-lactam ring

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

24
Q

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

A

7- 10 days after first exposure

1-2 days after repeat exposure

25
Q

What do penicillins interact with?

A

Methotrexate- they reduce renal excretion of methotrexate leading to toxicity

26
Q

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

A

Benzypenicillin (IV ONLY)- 1.2g QDS

Penicillin V (phenoxymethylpeniciilin) 500mg -1g QDS

27
Q

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?

A

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

28
Q

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?

A

Amoxicillin
Co-amoxiclav

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

29
Q

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

A

C.diff

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

30
Q

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

A

By killing normal gut flora that synthesise vitamin K

31
Q

Flucloxacillin is contraindicated in patients with prior flucloxacillin-related hepatotoxicity

A

Short half life (45 mins) therefor QDS administration

32
Q

Teicoplanin needs dose adjustment in renal impairment

A

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.

33
Q

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

A

Clarithromycin- a macrolide

34
Q

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

A

Atypical cover

e.g. Legionella and Mycoplasma pneuoniae

35
Q

What is the triple therapy for H.pylori?

A

Clarithromycin (macrolide)
+ Amoxicillin or Metronidazole
+ PPI

36
Q

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

A

Bind to the 50S subunit of bacterial ribosomes and inhibit bacterial protein synthesis

They are bacteriostatic (i.e stop growth)

37
Q

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

A

Prolong the QT INTERVAL

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

38
Q

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

A

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

39
Q

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

A

CNS toxicity including seizures

Should be used with caution in patients with epilepsy

Meropenem will also reduce plasma concentration of sodium valproate

40
Q

What antibiotics do we usually use for treatment of meningitis?

A

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

41
Q

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

A

Inhibit DNA synthesis

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

42
Q

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

A

They can lower seizure threshold so caution in EPILEPSY

Co-prescription of NSAID’s and quinolones increases seizure risk

QT PROLONGATION

Myasthenia graves

43
Q

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

A

Lower seizure threshold
Hallucination
Rupture of muscle tendons
QT interval prolongation

44
Q

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

A

It is a folate antagonist so it teratogenic in the first trimester

We should use Cefalexin for UTI’s in pregnancy

45
Q

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

A

Encephalopathy

Should never be given intrathecally (into spine)

46
Q

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?

A

CHOLESTATIC JAUNDICE

DIPLOMA (11 decks)

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