exam 4 Flashcards
Ideal Antibacterial drug
- Stability:
- Solubility
- Diffusibility: across BBB
- Slow excretion: protein binding/ drug combination
- Large therapeutic index: selective TD50/ED50
How do microbes respond to drug?
- resistance
2. secondary products of bacterial destruction
classification of antibacterial drugs
- bacteriostatic
2. bactericidal
considerations for antibacterial selection
- Prophylaxis
- Empiric therapy
- Pathogen-directed therapy
- Determine antibiotic sensitivity
- Location of infection
- Pharmacokinetics
- Resistant bacterial strains
- Virulent strains
- Host factors
- Antibiotic combination
What is prophylaxis?
temporarily decreases most likely pathogens below critical level required to cause infection
What is empiric therapy?
initiation of treatment before etiology of infection is known, with agents known to be effective against the most likely pathogen acquired. Can use a combination of antibiotic
What is pathogen-directed therapy?
Identification of bacterial species- Lab gram stain–> crystal violet
What is susceptibility-guided therapy?
Determining antibiotic sensitivity
- MIC: min. inhibitory concentration: lowest concentration of drugs which completely inhibit growth at 24hrs.
- MBC: min. bacterial concentration:
- Disk diffusion assays and E-test
How to avoid emergence of resistant micro-organisms?
use of drugs with the narrowest spectrum of activity
examples if antibiotic use in synergism:
- Beta lactam/ Penicillin: cell wall inhibitors. Allows aminoglycoside to enter the cell
- Aminoglycoside: protein synthesis inhibitors. Need to reach ribosome
Mechanisms of actions of antibacterials
- inhibition of nucleic acid synthesis
- DNA damaging agents
- inhibition of cell wall synthesis
- Damage of cell membrane
- inhibitors of protein synthesis
Penicillin classifications
- Naturally occurring: penicillin G and V. NARROW spectrum. against: strep. anaerobes, enterococcus, -
- Anti-staphlococcal: Methicillin, NARROW spectrum. against staphylococci, strep
- Amino- Penicillins: can be broken down by B-lactamases. BROADER spectrum. against: strep. enterococci, -, not pseudomonas
- Anti-pseudomonal: EXTENDED spectrum. against: strep. -, enterobacteriaceae & pseudomonas
What can be used to treat colitis?
- vancomycin best for severe colitis
- Metronidazole ( incorporates and damages DNA)
- Fidaxomicin ( transcription inhibitor of protein synthesis)
Which drugs are effective against Pseudomonas aeruginosa?
- Quinolones ( ciprofloxacin & levofloxacin)
- Anti-pseudomonal penicillin
- Ceftazidime(3rd generation cephalosporins)
- Cefepime (4th generration cephalosporins)
- CARBAPENEMS
- MONOBACTAMS
- Polymyxins
- Aminoglycosides
- Macrolides
- Ketolide
Which drugs are not effective against P. aeruginosa?
- Nitrofurans
2. Methenamine ( needs low PH bacteria raises it)
