Antimicrobials Flashcards
What are some general mechanisms of action of antibacterials?
Disrupt cell wall synthesis
Disrupt protein synthesis
Disrupt cell membrane function
Disrupt nucleic acid synthesis
Which classes of abx disrupt cell wall synthesis?
β-lactams
Glycopeptides
Which classes of abx disrupt protein synthesis?
Tetracyclines
Aminoglycosides
Macrolides
Which class of abx disrupt cell membrane function?
Polymixins
Which class of abx disrupt nucleic acid synthesis?
Quinolones
What are some examples of β-lactams?
Penicillins
Cephalosporins
Carbapenems
Monobactams
What are some penicillins, and what are they active against?
Penicillin; mainly Streptococci
Amoxicillin; some gram -ve
Flucloxacillin; Staph and Strep
Co-amoxiclav; Staph, Strep, anaerobes and gram -ve
What is an example of cephalosporin, and what is it active against?
Ceftriaxone
Broad spectrum, no anaerobe activity
Good activity in CSF (used for meningitis)
What is an example of a carbapenem, and what is it active against?
Meropenem
V broad spectrum
Most gram -ve
Generally used in penicillin allergy
Empiric treatment for sepsis
What is an example of a glycopeptide, and what is it active against?
Vancomycin
Active against most gram +ve
Requires therapeutic drug monitoring
What is an example of a tetracycline, and what is it active against?
Doxycycline
Broad spectrum, used in penicillin allergy for gram +ve
Used against atypical pathogens in pneumonia, chlamydia and some protozoa
What is an example of an aminoglycoside and what is it active against?
Gentamicin
Active against gram -ve
Reserved for gram -ve sepsis
What is an example of a macrolide, and what is it active against?
Erythromycin
Alternative to penicillin for mild gram +ve infections
Atypical respiratory pathogens
What is are examples of quinolones?
Ciprofloaxacin
Trimethoprim
How does ciprofloxacin exert its actions?
Inhibits DNA gyrase
V active against gram -ve and atypical pathogens
How does trimethoprim exert its actions?
Inhibits folic acid synthesis
Used for UTIs
When are abx used for prophylaxis?
Peri-operative;
Prevention of surgical site infection
1 dose just before surgery to last duration of procedure
Short term;
For pts who have had contact w/ meningitis - gets rid of N. meningitidis colonising oropharynx
Long term;
Asplenia, immunodeficiency
How are abx used to treat bacterial infections?
Empirical treatment for suspected infection
Treatment of culture proven infection
How is the likely cause of infection determined?
Duration of illness PMH Occupational hx Travel hx Time of year Age Personal background Anatomical site
How is an effective antibiotic determined?
Community or healthcare onset?
Severity of infection
Immune status of pt
Baseline rate of resistance
How is antibiotic activity determined?
Disc sensitivity testing
How do bacteria become resistant to abx?
Mutation of their own DNA
Acquiring resistance genes from other bacteria - horizontal transmission
What are some adverse effects of abx?
Organ toxicity
Allergic reactions
What are some specific abx toxicity, and the causative abx?
Nephrotoxicity - aminoglycosides, vancomycin
Hepatotoxicity - flucloxacillin
Ototoxicity - aminoglycosides
What are mechanisms of and resistance?
Antibiotic inactivation;
β-lactamase
Alteration of target site;
Penicillin binding protein
Alteration of metabolic pathways
Reduced intracellular abx accumulation;
Active efflux, decreased permeability of cell membrane
What is the minimum inhibitory concentration?
Minimum concentration of antibiotic required to inhibit growth of bacterium in vitro
How can antibiotic resistance be prevented?
Infection control
Appropriate prescribing
