Antimicrobials Flashcards by Caitlin Griffiths

In what ways can antibacterial agents be classified?

1) Bactericidal or bacteriostatic
2) Broad spectrum or narrow spectrum
3) Target site
4) Chemical structure

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What are the ideal feature of antimicrobial agents?

Selectively toxic
Few side effects
Able to reach infection site
Available as oral/IV formulation
Long half life (so infrequent dosing)
No interference with other drugs

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What are the four ways in which antibacterials can work?

1) Interruption of cell wall synthesis
2) Interruption of protein synthesis
3) Interruption of nucleic acid synthesis
4) Interruption of cell membrane function

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Which classes of antibacterials interrupt cell wall synthesis?

Beta lactams and glycopeptides

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What is an example of a beta lactam antibiotic?

Penicillins

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What is an example of a glycopeptide antibiotic?

Vancomycin

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Which classes of antibacterials interrupt protein synthesis?

Tetracyclines, aminoglycosides and macrolides

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Which class of antibacterials interrupts cell membrane function?

Polymixins eg colistin

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Which antibacterials work by interrupting nucleic acid synthesis?

Quinolones
Trimethoprim
Rifampicin

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How does penicillin work as an antibacterial?

Inhibit cell wall biosynthesis by inhibiting the formation of peptidoglycan cross-links

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What are some examples of penicillins?

Amoxicillin, Co-amoxiclav, Benzylpenicillin, Flucloxacillin

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What is amoxicillin usually used to treat?

Upper respiratory tract infections

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What are penicillins not effective against?

Staphylococcus

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What is Co-amoxiclav usually used to treat?

Pneumonia

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What is co-amoxicillin?

Amoxicillin and clavulanic acid

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What is flucloxacillin often used to treat?

Cellulitis, MSSA

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What is trimethoprim mainly used to treat?

Uncomplicated UTIs/bladder infections

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How does trimethoprim work?

Preventing the bacteria from producing folate. Without folate, the bacteria cannot produce DNA.

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What is rifampicin used to treat?

TB, meningitis prophylaxis

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What are the 3 types of resistance?

Intrinsic (usually permanent)

Acquired (new genetic material/mutates - usually permanent)

Adaptive (response to stress, usually reversible)

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What are some mechanisms of resistance?

Drug inactivating enzymes (eg b-lactamases)
Altered target (target enzyme has lowered affinity for antibacterial)
Altered uptake (eg reduced permeability or increased efflux)

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How does rifampicin work?

Inhibits RNA synthesis (inhibition of RNA polymerase)

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How can bacteria acquire resistance?

Chromosomal gene mutation or horizontal gene transfer

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What is conjugation?

Process by which one bacterium transfers genetic material to another through direct contact

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What is transduction?

Process by which foreign DNA is introduced into a bacterial cell by a virus (bacteriophage)

What is transformation?

Direct uptake, incorporation and expression of exogenous genetic material from the surroundings

How can you measure antibiotic activity?

Disc sensitivity testing and minimum inhibitory concentration

What does clavulanate inhibit?

B lactamase

What inhibits b lactamase?

Clavulanate, tazobactam

What are some cephalosporins?

Ceftriaxone, cefalexin, cefuroxime, cefotaxime

What is the cephalosporin group associated with?

C diff

What is ceftriaxone used to treat?

Meningitis (good activity in CSF)

What are some carbapenems?

Meropenem, imipenem

What is meropenem used to treat?

V broad spec | Most gram negs

What are the 4 classes of beta-lactams?

Penicillins, cephalosporins, carbapenems, monobactams

What are the generations of cephalosporins effective against?

First generation predominantly active against Gram-positive bacteria and successive generations have increased activity against Gram-negative bacteria Broad spectrum

What type of bacteria is vancomycin active against?

Most Gram positive bacteria (not Gnegs)

How does vancomycin work?

Inhibits cell wall synthesis

Why is vancomycin usually given intravenously?

It is not absorbed (oral for C diff only)

What is vancomycin usually given to treat?

C difficile, MRSA

What is vancomycin active against?

Staph auerus, streptococci, C difficile

How is tetracycline and doxycycline administered?

Orally

What is doxycycline usually used to treat?

Chlamydia, pneumonia (also alternative to penicillin)

Why shouldn't tetracyclines be given to children under 12?

Causes yellowing of teeth and bones

What is the most common aminoglycoside?

Gentamicin

How doe doxycycline work?

Inhibits protein synthesis

Which type of bacteria do aminoglycosides eg gentamicin have profound activity against?

Gram negative bacteria

True or False: Aminoglycosides have good activity in the CSF

False! Aminoglycosides have good activity in the blood/urine

What is gentamicin usually used to treat?

Serious abdominal infections Serious UTIs Endocarditis Gram neg sepsis

What can macrolides be used for?

Alternative to penicillin for mild Gram positive infections Also active against atypical respiratory pathogens

What is the most common example of a quinolone?

Ciprofloxacin

What do quinolones eg ciprofloxacin inhibit?

DNA gyrase

Which type of bacteria are quinolones active against?

Gram negative bacteria

Why is the use of quinolones limited?

Association with C difficile antibiotic-associated diarrhoea

What are azoles active against?

Yeasts +/- molds

What do azoles inhibit?

Cell membrane synthesis

What is used to treat Candida?

Fluconazole, nystatin (topical)

What are some polyenes?

Nystatin and amphotericin

What is used for the IV treatment of systemic fungal infections like aspergillus?

Amphotericin

What do polyenes inhibit?

Cell membrane function

What are some antivirals?

Aciclovir, oseltamivir

How does aciclovir work?

When phosphorylated, inhibits viral DNA polymerase

What is aciclovir used to target?

Herpes simplex and varicella zoster

How does oseltamivir work?

Inhibits viral neuraminidase

What is oseltamivir used to target?

Influenza A and B

What is metronidazole?

Antibacterial and antiprotozoal agent

How do cephalosporins work?

Inhibit cell wall synthesis

How does metronidazole work?

Inhibits nucleic acid synthesis

How does doxycycline wokr?

Interrupts protein synthesis

What is benzylpenicillin used to treat?

Strep endocarditis, neonatal sepsis

What is tazocin?

Piperacillin + tazobactam

What is tazocin used to treat?

Pseudomonal infections

How does gentamicin work?

Interrupts protein synthesis

What are some macrolides?

Erythomycin and clarithromycin

How does erythromycin work?

Interrupts protein synthesis

What is ciprofloxacin active against?

G negs