Antibiotics Flashcards
What are the main targets of antibiotics
Cell wall synthesis
Protein synthesis
DNA synthesis
What are the types of antibiotics that target cell wall synthesis
Beta lactams:
Penicillins
Cephalosporin
Carbopenems
Glycopeptides:
Vancomycin
Teicoplanin
What is mechanism of action of beta lactams
Remove cross links between peptidoglycan cell wall layers
Give examples of penicillins and their indications
Amoxicillin: Broad spectrum
Flucloxacillin: staphylococcal soft tissue infections
Benzylpenicllin: Gram +ves
Co-amoxiclav, Tazobactam: beta lactaminase inhibitor combinations
Give examples of cephalosporins and their indications
Ceftriaxone
Meningitis
Give examples of carbopenems and their indications
Meropenem
Sepsis
V broad spectrum (inc anaerobes)
What is mechanism of action of glycopeptides
Prevents cross link formation between peptidoglycan cell wall layers
Give examples of glycopeptides and their indications
Vancomycin, Teicoplanin
Gram -ves
Narrow therapeutic window - monitoring required
What are types of antibiotics that target protein synthesis
Aminoglycosidases
Tetracyclines
Macrolides
What is mechanism of action of aminoglycosidases
Inhibit 30s ribosome
Inhibit mRNA translation into proteins
Give examples of aminoglycosidases and their indications
Gentamicin
Gram -ve sepsis
Narrow therapeutic window - monitoring required
What is mechanism of action of tetracyclines
Lock tRNA to septal site of mRNA
Give examples of tetracyclines and their indications
Tetracycline, Doxycycline
Broad spectrum
Chlamydia, Mycoplasma, Atypical pathogens of pneumonia
What is mechanism of action of macrolides
Inhibit 50s ribosome
Inhibit translation of mRNA to proteins
Give examples of macrolides and their indications
Erythromycin, gentamicin, azithromycin
Similar spectrum to penicillins
Penicillin allergic patients
Azithromycin - gonadal chlamydia trachomatis infection
What are types of antibiotics that target DNA synthesis
Quinolones
Folic acid inhibitors
Metronidazole
What is mechanism of action of quinolones
Inhibit DNA gyrase
Inhibit supercoiling of DNA
Leads to DNA damage
Give examples of quinolones and their indications
Ciprofloxacin Broad spectrum: G +ve, -ve, Atypicals Urinary tract sepsis Biliary tract sepsis Campylobacter food poisoning
What is mechanism of action of folic acid antagonists
Inhibit DHFR, inhibit folic acid metabolism
Inhibit nucleic acid synthesis
Give examples of folic acid antagonists and their indications
Trimethoprim, sulphonamide
Uncomplicated UTI
PCP Prophylaxis and treatment - co-trimoxazole
What is mechanism of action of metronidazole
Form toxic metabolites that inhibit nucleic acid synthesis
What are indications of metronidazole
Pseudomembranous colitis
Protozoan infection: Giardia, Trichomonas vaginalis, Entamoeba
What are mechanisms of antibiotic resistance
Vertical: Chromosomal gene mutations
Horisontal:
Transduction - gene transfer by bacteriophage
Conjugation - uptake of plasmids
Transformation - uptake of foreign DNA
What are the types of antibiotic resistance
Antibiotic inactivation: e.g. beta lactaminase
Altered target site
Altered uptake: increased efflux mechanism, decreased permeability
How can you prevent antibacterial resistance
Antimicrobial stewardship: Right antibiotic Right time Right dose, frequency, duration Right route
What factors determine right antibiotic
Cause of infection: history, duration of infection, site of infection
Drug efficacy: level of resistance (community/hospital acquired), immune status, severity of infection
Safety: allergy, toxicity, drug interactions
What factors determine right dose, frequency, duration
PK and PD of antibiotic
What are PD effects of antibiotic dependent on
Minimum inhibitory concentration
Time above MIC
Concentration above MIC
What is time dependent killing
Successful treatment depends on prolonged presence at infection site
Time>MIC value high
What is concentration dependent killing
Successful treatment depends on high concentration at infection site
Cmax:MIC value high
