Microbio - antimicrobials Flashcards by P K

Most common systems affected in adverse reactions to ABx

GI upset
Rash
Renal dysfunction
Anaphylaxis!!
Hepatitis

How well did you know this?

Not at all

Perfectly

Name 2 Abx commonly causing renal dysfunction

Gent + Vanc

How well did you know this?

Not at all

Perfectly

4 things to consider when choosing an abx for an individual

Host characteristics (age? disease?)
Antimicrobial susceptibilities
Organism
Site of infection

How well did you know this?

Not at all

Perfectly

Methods of identifying infecting organism?

Gram stain: from CSF, pus, joint aspirate

Immunofluorescence or PCR to identify an antigen rapidly

How well did you know this?

Not at all

Perfectly

What clinical features of a patient would make you consider using an Abx?

systemic response: fever, neutrophilia (neutropenia in severe infection), raised CRP

How well did you know this?

Not at all

Perfectly

When to switch from IV to po?

After 48 hours if pt has stabilised

How well did you know this?

Not at all

Perfectly

3 patterns of Abx activity

Concentration dependent killing (max concentration of drug)
Time dependent killing (time that drug conc’n is above MIC)
Both

How well did you know this?

Not at all

Perfectly

Concentration-dependent Abx?

Aminoglycosides

How well did you know this?

Not at all

Perfectly

Time-dependent abx?

penicillins

How well did you know this?

Not at all

Perfectly

Recommended time of abx course for simple cystitis? gp a strep throat?

3 days - cystitis

10 days - strep throat

How well did you know this?

Not at all

Perfectly

N. meningitidis meningitis - length of abx course?

7 days

How well did you know this?

Not at all

Perfectly

Length of abx course for bacterial endocarditis? for acute osteomyelitis?

IE: 4-6 weeks

osteomyelitis - 6 weeks

How well did you know this?

Not at all

Perfectly

Typical Abx for cellulitis/

flucloxacillin unless allergic or MRSA. MRSA –> vancomycin

How well did you know this?

Not at all

Perfectly

Typical Abx for pharyngitis? how long for?

Benzylpenicillin for 10 days

How well did you know this?

Not at all

Perfectly

Typical Abx for CAP - mild and severe?

mild = amoxicillin
severe = coamoxiclav + clarithromycin

How well did you know this?

Not at all

Perfectly

Typical Abx for HAP?

amoxicillin + gentamicin or tazocin

How well did you know this?

Not at all

Perfectly

typical antibiotic for bacterial meningitis?

What is the exception?

Ceftriaxone

Or amoxicillin if young/old/immunocomp due to risk of listeria

How well did you know this?

Not at all

Perfectly

typical Abx for UTI - community? hospital?

community = trimethoprim
Nosocomial = co-amoxiclav/cephalexin

How well did you know this?

Not at all

Perfectly

Typical Abx for Sepsis - severe?

Ceftriaxone/tazocin, metronidazole +/- Gentamicin

How well did you know this?

Not at all

Perfectly

Typical Abx for Neutropenic sepsis?

Tazocin + gentamycin

How well did you know this?

Not at all

Perfectly

Typical Abx Mx for C-difficile colitis

STOP the cephalosporins!!!
Start with metronidazole PO.
If ineffective, use vancomycin

How well did you know this?

Not at all

Perfectly

3 types of beta lactams

pencillins
cephalosporins
carbapenems

How well did you know this?

Not at all

Perfectly

Name 4 penicillins and state what they vs

1) penicillin
2) amoxicillin - also cover enterococci + E. Coli!!!!
3) flucloxacillin - resistant to b-lactamases
4) piperacillin - also against pseudomonas + non-GI gram -ves

How well did you know this?

Not at all

Perfectly

2 useful things to use with Abx?

clavulanic acid and tazobactam

How well did you know this?

Not at all

Perfectly

How do the cephalosporins change from 1st --> 3rd gen?

Increased Gram -ve activity

Which cephalosporin is 2nd gen?

Cefuroxime

Which cephalosporin is assoc. with C. Difficile?

Ceftriaxone

Name the cephalosporin which covers Pseudomonas? which bacteria does it not cover?

Ceftazidime! Doesn't cover any Gram +ve

Why were carbapenems developed?

bacteria developed extended spectrum beta lactamases, therefore resistant to cephalosporins

Name some carbapenems? Which things are resistant to them now?

Merapenem, Ertapenem | - MDR klebsiella, MDR acinetobacter

Advantages of using b-lactams?

Short half life Relatively non-toxic Doesn't cross the BBB

Which cell wall synthesis inhibitors cannot be used against Gram-ves?

Glycopeptides - can't penetrate the gram -ve cell wall

Name 2 glycopeptides

vancomycin, teicoplanin

What are glycopeptides particularly useful vs?

MRSA, C. Difficile, enterococci

What type of Abx is gentamicin? | MOA?

Amino glycosides! Binds to 30S ribosomal subunit - inhibits elongation of pp chain + causes misreading of codons from mRNA. Conc'n dependent

What are aminoglycosides particularly useful vs?

Neutropenic gram -ve sepsis, Pseudomonas

Doxycycline - which Abx class is it in? What is it useful against?

Tetracyclines | Intracellular organisms - chlamydiae, rickettsiae, mycoplasmas

Special considerations with tetracyclines?

Don't give to children + pregnant women | - Causes a light sensitive rash

Name 3 macrolides.

Erythro/clarithro/azithromycin

MOA of macrolides

Bind to 50S ribosomal subunit Interfere with translocation

Usefulness of macrolides vs?

Against strep/staph if penicillin allergic Campylobacter, Legionella (CAP) S. Typhi (w azithromycin)

Chloramphenicol - why isn't it used much? How is it used now - give 2 uses? MOA?

- Risk of aplastic anaemia + grey baby syndrome - Bacterial conjunctivitis + meningitis if pen-allergic - Binds to 50S ribosomal subunit - inhibits translation

Linezolid - MOA?

- Prevents formation of 70S initiation complex | -

Linezolid - USE?

GRAM +VES ONLY | esp MRSA + VRE

Quinolone - eg? MOA?

Ciprofloxacin, levofloxacin Binds to alpha subunit of DNA gyrase

Quinolones - 2 bacteria it is used against?

pseudomonas + chlamydia

Eg of nitroimidazoles?

metronidazole

2 useful groups which metronidazole is used against? give eg of each?

Protozoa and Anaerobes | Giardia + C Diff.

Name an RNA synthesis inhibitor?

RIfampicin

What does rifampicin bind to? what precautions must be taken - name 4

Binds to DNA dependent RNA polymerase - MONITOR LFTs - single a.a. change --> resistance therefore NEVER use alone - Turns secretions orange - DDIs - eg COC

name 2 cell membrane toxins

Daptomycin + Colistin.

When is colistin used? SE?

Last line for MDR- bacteria. eg klebsiella, acinetobacter, pseudomonas - last line as it is nephrotoxic!

Name some useful folate metabolism inhibitors and what they're used against

Co-trimoxazole - PCP | Trimethoprim - community UTI

4 mechanisms of Abx resistance

``` BEAT Bypassing Abx-sensitive step of pathway Enzyme mediated inactivation of Abx Accumulation impairment (efflux of abx from cell) Target alteration ```

2 main modes of resistance against beta lactams?

Enzyme mediated inactivation - beta lactamases | Target alteration - mecA gene by MRSA and PBP mutation in pneumococcus

Give e.g.s of 2 bacteria which have altered their target to become resistant to beta-lactams?

MRSA - mecA gene = encodes a novel PBP 2a Pneumococcus - multiple PBP gene mutations

Macrolides - how have bacteria become resistant to them?

Erm gene encode for target alteration --> reduced binding of macrolides

Good prophylactic Abx for splenectomy patients against S. pneumonia?

Amoxicillin

2 major side effects of amoxicillin

Anaphylaxis | Steven Johnsons

Trimethoprim: MOA?

Folate antagonist

3 side effects of trimethoprim

- Megaloblastic anaemia - Low platelets - Hyperkalemia (by inhibiting DCT Na channels)

Abx against N. meningitidis

Cefotaxime

MOA of vancomycin

Glycopeptide which inhibits cell wall synthesis

What precautions are taken when giving vancomycin and why?

Vancomycin serum levels need to be monitored when given due to extensive side effects: - Kidney failure - Ototoxicity - Anaphylaxis - Blood disorders - Rash