Antimicrobials Flashcards
What is MIC?
Minimum Inhibitory Concentration
lowest concentration of antibiotic required to prevent growth
What is MBC?
Minimum Bactericidal Concentration
Lowest concentration required to kill bacteria
What meds are bacteriostatic?
Tetracyclines Chloramphenicol Erythromycin Sulfonamides Trimethmprim
- others are bactericidal.
- bactericidal not better than bacteriostatic
What are 3 narrow spectrum meds?
PCN G
Erythromycin
Clindamycin
Name some broad spectrum meds?
Ampicillin Cephalosporins aminoglycosides tetracyclines chloramphenicol quinolones
Time-dependent killing
clinical efficacy is related to the duration for which these levels are maintained
*continuous infusion has not shown to be more effective than intermittent boluses
Concentration dependent killing
some meds increase the rate and extent of bacterial killing with increasing concentrations
What is post-antibiotic effect (PAE)?
some antibiotics continue to suppress growth of bacteria even after antibiotic is no longer detectable.
demonstrated for virtually all antimicrobials
decreased in acidic (infected) media
This is the judicious use of antibiotics to reduce resistance development
antimicrobial stewardship
What med is frequently used for UTIs that contributes to resistance
Cipro –> broad spectrum, not necessary
What is intrinsic resistance
natural resistance to antimicrobial
ex: vanco only kills gram positive bacteria
What is acquired resistance?
a genetic alteration in the bacteria that renders a once effective antimicrobial ineffective
What are 4 mechanisms of acquired resistance?
decreased permeability
increased efflux pumps
inactivation
modification of the antimicrobial target
What is a polymicrobial infection?
more than 1 drug may be needed to treat infection with more than 1 organism
*Broad spectrum may be able to cover multiple organism infection with a single agent
Why might you use 2 antibiotics with different mechanisms of action?
To inhibit emergence of resistant strains of an organism
T/F: there is evidence showing benefit to using “double coverage” to treat infection
FALSE
no proven benefit to giving 2 susceptible antibodies as opposed to just one
Name the different types of synergy;
a. 1+1 = 0.5
b. 1+1 = 1
c. 1+1 = 1.5
d. 1+1 = 2
e. 1+1 = 3
a. antagonism
b. indifferent
c. in between
d. additive
e. synergistic
What are 5 instances when bactericidal therapy may be necessary for clinical cure
- CV infection - endocarditis
- Meningitis and cerebral abscess
- Invasive bacterial infection in severely neutropenic pt
- Osteomyelitis
- Attempted treatment of prosthesis or vascular access related infections w/o removing the device
What can increase a pt’s risk for a specific type of infection?
neutropenia asplenia malignancy HIV immunosuppressant therapy
What 2 things increase a pt’s risk for complications from an infection?
- Prosthesis or foreign body; heart valves, prosthetic joints, vascular grafts *form a biofilm
- Pregnant pts: pharmacokinetics are altered - increased volume of distribution and GFR
What antibiotics are ok to give to pregnant pts?
PCNs - study said to avoid 1st trimester
Cephalosporins
Erythromycin
What antibiotics should you avoid in pregnancy bc will cause injury to fetus?
metronidazole, ticarcillin, rifampin, trimethoprim, fluoroquinolones, and tetracyclines
*tetracycline associated with acute fatty necrosis of the liver, pancreatitis, and possible renal injury - it also discolor teeth
what percentage of pts with PCN allergy will have a reaction to cephalosporins?
< 2-5%
What 3 devices are highly associated with nosocomial infections?
ventilator
vascular access catheter
urethral catheter
