Antimicrobials Flashcards
In what ways can antibacterial agents be classified?
1) Bactericidal or bacteriostatic
2) Broad spectrum or narrow spectrum
3) Target site
4) Chemical structure
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
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
Which classes of antibacterials interrupt cell wall synthesis?
Beta lactams and glycopeptides
What is an example of a beta lactam antibiotic?
Penicillins
What is an example of a glycopeptide antibiotic?
Vancomycin
Which classes of antibacterials interrupt protein synthesis?
Tetracyclines, aminoglycosides and macrolides
Which class of antibacterials interrupts cell membrane function?
Polymixins eg colistin
Which antibacterials work by interrupting nucleic acid synthesis?
Quinolones
Trimethoprim
Rifampicin
How does penicillin work as an antibacterial?
Inhibit cell wall biosynthesis by inhibiting the formation of peptidoglycan cross-links
What are some examples of penicillins?
Amoxicillin, Co-amoxiclav, Benzylpenicillin, Flucloxacillin
What is amoxicillin usually used to treat?
Upper respiratory tract infections
What are penicillins not effective against?
Staphylococcus
What is Co-amoxiclav usually used to treat?
Pneumonia
What is co-amoxicillin?
Amoxicillin and clavulanic acid
What is flucloxacillin often used to treat?
Cellulitis, MSSA
What is trimethoprim mainly used to treat?
Uncomplicated UTIs/bladder infections
How does trimethoprim work?
Preventing the bacteria from producing folate. Without folate, the bacteria cannot produce DNA.
What is rifampicin used to treat?
TB, meningitis prophylaxis
What are the 3 types of resistance?
Intrinsic (usually permanent)
Acquired (new genetic material/mutates - usually permanent)
Adaptive (response to stress, usually reversible)
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)
How does rifampicin work?
Inhibits RNA synthesis (inhibition of RNA polymerase)
How can bacteria acquire resistance?
Chromosomal gene mutation or horizontal gene transfer
What is conjugation?
Process by which one bacterium transfers genetic material to another through direct contact
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