Principles of Antimicrobial therapy Flashcards
(33 cards)
Prophylaxis
ABTs given before certain medical procedures or before symptoms start in anticipation fro obtaining an infection
Empiric therapy
Therapy should be initiated after specimens for laboratory analysis have been obtained, but before the results of the culture are available. Drug choice is usually based on patient’s history, such as previous history, previous infections, travel history etc.
Definitive therapy
Administration of ABTs for a know bacteria, more specific ABT can be used after pathogen is cultured.
Normal flora
Bacteria which are found in or on our bodies on a semi-permanent basis without causing disease, particularly important in the enlarge intestine, but also found in the nose, mouth, throat, and skin.
Colonization
the development and growth of a bacterial infection on an individual, as demonstrated by a positive culture. The infected person may have no signs or symptoms of infection while still having the potential to infect others
Superinfection
Drug therapy, particularly with broad-spectrum antimicrobials or combinations of agents, can lead to alterations of the normal microbial flora of the upper respiratory, intestinal, and genitourinary tracts, permitting the overgrowth of opportunistic organisms.
Bactericidal
a substance that kills bacteria. Bactericides are disinfectants, antiseptics, or antibiotics
Bacteriostatic
arrest the growth and replication of bacteria at serum (or urine) levels achievable in the patient, thus limiting the spread of infection until the body’s immune system attacks, immobilizes and eliminates the pathogen
Minimum inhibitory concentration (MIC)
the lowest concentration of ABT that inhibits bacterial growth. To provide effective ABT the clinically available concentration in the body should be above the MIC
Minimum bactericidal concentration (MBC)
The minimum amount of ABT that kills the bacteria under investigation. The amount of ABT that results in 99.9% decline in colony count after overnight dilution incubations.
Host characteristics to consider with ABT
immune system status renal dysfucntion hepatic dysfunction poor perfusion age pregnancy/lactation genetics
Additive (indifferent) effect
the activity of two drugs in combination is equal to the sum (or a partial sum) of their independent activity when studied separately
synergistic effect
the activity of two drugs in combination is great to the sum of their independent activity when studied seperately
combination therapy
can potentially increase the effectiveness of an ABT and reduce the risk of resistance. It also increases the spectrum of activity when the organism causing diseases unknown or if there are multiple organisms causing disease
Aminoglycosides
MOA:Diffuses through porin channels, interferes with assembly of proteins by binding to 30S ribosome
Spectrum: Gram - aerobic organisms
Example: streptomycin
Beta-lactams (penicillins)
MOA: Interferes with the peptidoglycan cell wall synthesis, prevents formation of cross linkages, bactericidal
Spectrum: Gram + organisms
Beta-lactams (cephalosporins)
MOA: Interferes with the peptidoglycan cell wall synthesis, prevents formation of cross linkages, bactericidal
Spectrum: Gram + organisms (different generations)
used for staph and strep
Glycopeptides
MOA: inhibits synthesis of bacterial cell wall phospholipids as well as peptidoglycan polymerization, weakens cell wall and damages underlying cell membrane
Spectrum: Gram + and MRSA, Gram + anaerobes
Ex: vancomycin
Macrolides
MOA: Bind irreversibly to site on the 50S ribosome, inhibiting protein synthesis. Bacteriostatic (can be cidal at higher doses)
Spectrum: Gram + and Gram -; anaerobic
Ex: azithromycin
Tetracyclines
MOA: Binds reversibly to the 30S subunit, inhibiting protein synthesis
Spectrum: Broad spectrum; effective against Gram+ and Gram - bacteria
Quinolones
MOA: Enter the organisms outer membrane by passive diffusion through porins, interfere with DNA replication by interfering with DNA gyrase and topoisomerase IV
Spectrum: Gram - ; gonorrhea
Sulfonamides
MOA: inhibit the synthesis of bacterial dihydrofolic acid and the formation of its cofactors, Bacteristatic
Spectrum: Active against sellected Enterobacteria in the urniary tract and nocardia, listeria, PCP, S aureus, S pneumonia, H influenzae, many gram -
Acyclovir (Zovirax)
valcyclovir (Valtrex)
nucleoside analogs
MOA: They work as antimetabolites by being similar to nuclesides, they act as chain terminators and stop viral DNA polymerase, they are not specific to viral DNA and can affect mitochondrial DNA aswell.
Indications: hep B & C, herpes simplex viruses
protease inhibitors
indinavir (Crixivan)
saquinavir (Invirase)
MOA:prevent viral replication by selectively binding to viral proteases and blocking proteolytic cleavage of protein precursors that are necessary for production of viral particles
Indications: HIV/AIDS, Hep C
