Test 5: Antibiotics (Bacteria) Flashcards
What is Gram Staining?
The first step in the identification of a bacterial organism.
-Staining with crystal violet dye differentiates bacteria by the chemical and physical properties of their cell walls by detecting peptidoglycan
-Peptidoglycan: present in a thick layer in gram-positive bacteria
-Not all bacteria can be classified by this technique - some are gram variable
What is the response to gram-positive vs gram-negative bacteria to gram staining?
Gram-positive bacteria retain the crystal violet dye
Gram-negative bacteria stain a red or pink coloring 2/2 a counterstain (commonly safranin or fuchsine)
What is a Culture & Sensitivity?
Culture: Identifying the organism
Sensitivity: Identify the susceptibility/resistance of the bacteria to the selected ABX (which agent will kill it)
Especially important with Gram (-) due to the high incidence of drug-resistant organisms
What must be intact for antibiotics to work?
The acquired immune system.
-Effectiveness of antibiotic therapy may depend on acquired immune responses
Why does scheduling and time intervals matter with antibiotics?
Compliance with proper time intervals maintains the MEC/MIC (minimum effective/inhibitory concentration).
What does it mean if an organism is Susceptible?
Requires a low or moderate MIC/MEC that can be attained by giving usual doses of an ABX.
What does it mean if an organism is Resistant?
Requires a high MIC/MEC, and may require higher concentrations of drugs than can be achieved in the body even with large doses.
-Can be due to over use of inappropriately prescribed ABXs (ex: prescribing abx for a viral infection)
-Ex: MRSA, VRE
What are International Units (IU)?
-Unit of measurement for the amount of a substance
-The mass or volume that constitutes one international unit varies based on which substance is being measured
-Variance is based on the biological activity or effect for the purpose of easier comparison across substances
-Used to quantify vitamins, hormones, some medications, vaccines, blood products, and similar biologically active substances.
What are the general pharmacokinetics of Antibiotics?
Absorption:
-Oral bioavailability greater than 70% for most antibiotics
IV route preferred route for treatment of serious infections
Distribution:
-Varies based on agent and location of infection
Metabolism:
-Varies
-Hepatic vs excreted unchanged in kidneys
Elimination:
-All routes: renal, EHC, lactation
What is the usual duration of therapy for acute infections?
Average 7-10 days, or until the patient is asymptomatic/afebrile for 48-72 hours (after initial therapy is completed)
-If initial therapy doesn’t work, need to switch to a different ABX. Continue therapy for 48-72 hrs afebrile.
What is unique about the Sulfonamides?
-They are lipid soluble to be able to enter the tissues, but then are biotransformed to water soluble and stay in the urinary system. Good for UTIs.
-Sulfa allergies can be an issue in generic form of propofol (issue in someone with sulfa allergy and pt with asthma).
-Preservative in generic propofol called sodium metabisulfite. Concern for cross allergy with sulfa.
What are the 4 Mechanisms of Action for antibiotics?
1) Inhibitors of folic acid and nucleotide biosynthesis
-Sulfonamides
2) Bacterial Cell wall synthesis inhibitors
-PCN
-Cephalosporins
-Vancomycin
-Aztreonam
3) Inhibitors of DNA replication & RNA synthesis
-Quinolones
-Rifampin
4) Protein Synthesis Inhibitors:
-Tetracycline
-Aminoglycosides
-Microlides
-Isoniazid
What hypersensitivity reaction can occur with antibiotics?
Usually Type 1.
-Skin rash to Anaphylaxis.
-IgE mediated
How do superinfections occur?
Antibiotics kill normal body flora, making room for opportunistic infections.
-C. Diff
-Thrush
What are common organ toxicities associated with antibiotics?
-Ototoxicity
-Nephrotoxicity
-Cardiotoxicity
-Neurotoxicity (seizures)
-Hemolytic anemias
