Session 4: Antimicrobials Flashcards
Classes of antibacterials by their mechanism of action.
Antibacterials which interrupt cell wall synthesis.
Antibacterials which disturb cell membrane function.
Antibacterials which disturb protein synthesis.
Antibacterials which disturb nucleic acid synthesis.
Which antibacterials interrupt cell wall synthesis?
Beta-lactams like pencilling and cephalosporins
Glycopeptides
Vancomycin
Which antibacterials disturb cell membrane function?
Polymixins
Which antibacterials disturb protein synthesis?
Tetracyclines
Aminoglycosides
Macrolides
Which antibacterials disturb nucleic acid synthesis?
Quinolones
Trimethoprim
Rifampicin
Give types of resistance.
Intrinsic
Acquired
Adaptive
Explain intrinsic resistance.
There is no target or access for the drug which is usually permanent resistance.
Explain acquired resistance.
Acquires new genetic material or mutates which is also usually permanent.
Explain adaptive resistance.
The organism responds to a stress like sub-inhibitory level of antibiotic.
Give mechanisms of resistance.
Enzymatic modification or destruction of antibiotics.
Enzymatic alteration of antibiotic targets.
Mutations of bacterial target sites.
Give examples of penicillins.
Penicillin V Amoxicillin Flucloxacillin Co-amoxiclav Tazocin
Give examples of cephalosporins
Ceftriaxone
Ceftazidime
What is penicillin most effective against?
Streptococci
What is amoxicillin most effective against?
Streptococci + some activity against gram-negatives.
What is flucloxacillin most effective against.
Both staphylococci and streptococci.
What are Co-amoxiclav effective against?
Streptococci, staphylococci, anaerobes and gram-negatives.
What is piperacillin/tazobactam effective against?
Streptococci, staphylococci, anaerobes, gram-negatives and pseudomonas.
Give features of cephalosporins in their effectiveness against microbes.
Generations which have gone up and own between gram negative and positive. More effective against gram negative than positive.
There is a broad spectrum but no anaerobic activity.
What is ceftriaxone particularly good at?
Good activity in cerebral spinal fluid.
Side-effect of ceftriaxone.
Associated with Clostridium difficile
What are carbapenems?
Beta-lactams which act on cell wall synthesis.
Give examples of carbepenems.
Meropenem, ertapenem, imipenem.
Give features of carbapenems in their effectiveness.
Very broad spectrum including anaerobes
Active against most but not all gram negatives.
Generally safe in penicillin allergy so often considered the reserve antibiotic for gram-negative infections.
Give examples of glycopeptides.
Vancomycin and Teicoplanin.
Give features of vancomycin.
Active against most gram positives but not gram negatives.
Active against some enterococci resistant.
Resistance in staphs is rare
It is not absorbed so given orally only for clostridium difficile (so usually administered IV)
Narrow therapeutic window
Main difference between Teicoplanin and Vancomycin.
Teicoplanin is easier to administer
Features of tetracycline and doxycycline.
Disturb protein synthesis.
Similar spectrum and both are given orally.
Broad spectrum but specific use in penicillin allergy for gram positives
Active in atypical pathogens in pneumonia
Active against chlamydia and some protozoa
Should be given to children, pregnant and breastfeeding women.
Features of aminoglycosides.
Most common agent is gentamicin.
Profound activity against gram negatives.
Good activity in blood and urine.
Potentially toxic to kidneys and to ears.
Narrow therapeutic window
Generally reserved and most important for severe gram negative sepsis.
Features of erythromycin and clarithromycin (Macrolides).
Well distributed including intracellular penetration.
Alternative to penicillin for mild gram positive infections.
Also active against atypical respiratory pathogens.
Features of quinolone.
Commonest example is ciprofloxacin
Inhibits DNA gyrase
Very active against gram negatives
Active against atypical pathogens
Side-Effects of quinolone.
Increasing resistance and risk of C. difficile
Also associated with tendinitis and rupture, aortic dissection and CNS effects.
Features of trimethoprim and sulphonamides.
Inhibitors of folic acid synthesis
Trimethoprim is used alone in the UK for UTIs
Used to treat pneumocystis jirovecii and has activity against MRSA when used with sulphamethoxazole
Give types of antifungals.
Azoles and Polyenes.
Features of Azoles
Inhibit cell-membrane synthesis. Fluconazole used to treat Candida albicans (thrush)
Itra/Vori/posaconazole also active against Aspergillus
Active against yeasts +/- holds.
Features of polyenes.
Inhibits cell membrane function.
Nystatin for topical treatment of Candida
Amphotericin for IV treatment of systemic fungal infections like Aspergillus.
Give examples of antivirals.
Aciclovir
Osteltamivir (Tamiflu)
Features of aciclovir.
When phosphorylated it inhibits viral DNA polymerase.
Effective against Herpes simplex like genital herpes and encephalitis
Effective against Varicella zoster like chicken pox and shingles.
Features of Oseltamivir (Tamiflu)
Inhibits viral neuraminidase
Effective against influenza A and B
Give an example of a drug that is both an antibacterial and antiprotozoal agent.
Metronidazole.
Features of Metronidazole.
Active against anaerobic bacteria.
Active against protozoa like amoebae, giardia and trochomonas.
