Flashcards in Abx Deck (69):
What is meant by the term, "selective toxicity"?
The ability to kill or inhibit growth of a microorganism without harming host cells
What is the difference between an antibiotic and an antimicrobial?
Abx = naturally derivedAntimicrobial = lab derived
What is bacteriostatic?
Inhibiting growth of bacteria, but not actually killing them
What is bactericidal?
When would you use a bacteriostatic drug?
When host defenses can be counted on
When would you use a bactericidal drug?
Immunocompromised, prophylacticly, or with lethal strains of bacteria
What is antibiotic synergism?
When a combination of two or more abx have an enhanced activity when administered together
What is antibiotic antagonism?
When a combination of abx interfere with one another, and reduce overall effectiveness
What are broad spectrum abx?
Abx that are effective against a large variety of bacteria
What are the advantages and disadvantages of broad spectrum abx?
Advantage = kill w/o knowing etiologyDisadvantage = kill gut flora
What are narrow spectrum abx?
Abx that are effective against only a small subset of bacteria
What are the advantages/disadvantages of using narrow spectrum abx?
Advantage: Avoid disrupting normal floraDis: must have specific disease to target
Do abx cause resistance?
No, genetic mutations do
What are the three results of an abx test?
What would you do if you had an intermediate resistance abx, if you still wanted it to be effectie
Target the abx to the body sites and increase dosage
Why should pts alway finish their dose of abx?
To allow immune system to kill off any surviving resistant cells
What is empiric therapy for abx?
Treatment while waiting for lab results (broad spectrum abx)
What are the pharmacokinetic/pharmacodynamic properties of abx that must be considered when administering abx?
Concentration of abx at site of infection must be adequate for a prolonged duration
What are the four ways that bacteria break down/avoid death by abx?
1. Hydolysis2. Chemical modification3. Alteration of target4. Altered permeability5. Lack of target
What is the MIC?
Minimal inhibitory concentration- A measure of the lowest concentration of the antimicrobial agent that **inhibits** visible growth of bacteria after 18-24 hours of incubation
What is the MBC?
Minimal bactericidal concentration (MBC) – the lowest concentration of antibiotic **without** visible bacterial growth on agar after 18-24 hours incubation.
What is the E-test?
Strips of varying [C] of abx placed on an agar plate with bacteria multiplying.
What is the disk diffusion assay (Kirby-Bauer test)?
When discs are placed on an agar plate with bacteria dividing
What does it mean for an abx to be cell wall active?
it disrupts peptidoglycan synthesis
What are cell wall active abx effective against/what must the bacteria be doing for it to take effect?
What are membrane active abx?
Abx that interfere or disrupts with the membrane
Are membrane active abx effective against resting or actively dividing bacteria? How about cell wall active?
Membrane active effective against bothCell wall active only effective against dividing bacteria
What is the MOA of Beta-lactams?
Inhibits cell wall synthesis
What type of abx are penicillins?
What type of abx are cephalosporins?
What type of abx are cephamycins?
What type of abx are carbaenems? Monobactams?
What is the enzyme that penicillin disrupts? What is the function of this enzyme?
Penicillin binding proteins/transpeptidases.This enz crosslinks L-lysine to an alanine in the NAM/NAG of the peptidoglycan chain
Are beta-lactams bacteriocidal or inhibitory?
What type of bacteria are B-lactams ineffective against?
against species that lack cell wall (e.g. Mycoplasma), those with very impenetrable walls, or those that produce Beta-lactamase
What is the difference between cephalosproins and penicillin?
Cephalosporins are more resistant to B-lactamase, and have a longer half-life
What are the ways in which resistance to B-lactams is brought about? (4)
1. Altered transpeptidases2. Altered outer membrane permeability3, Presence of efflux pumps4. Chemical modification of abx
What is the MOA of Vancomycin?
Recognizes and binds to the two D-alanine residue ands of the peptide cchaines of NAM//NAG in peptidoglycan, preventing transpeptidase function
How is resistance to Vanco brought about?
By changing the D-ala residue on the NAM to a D-lactate, preventing the binding of vanco
What is the MOA of bacitracin?
Interferes with dephosphorylation of bactoprenol, which carries NAM/NAG residues from the inner to the outer surface of a cell membrane
Are tetracyclines bacteriostatic or bacteriocidal?
What is the MOA of tetracyclines?
inhibit protein synthesis by binding to the 30S ribosomal subunit of the ribosome and inhibiting the binding of the amino-acyl tRNA to the mRNA-ribosome complex.
Do tetracyclines act on both gram positive and gram negative bacteria?
Are tetracyclines considered broad or narrow spectrum abx?
What is the MOA of aminoglycosides?
They irreversibly bind to the 30S ribosomal subunit
Are ainoglycoside generally bactericidal or bacteriostatic?
What type of bacteria are aminoglycosides ineffective against?
What type of abx is gentamycin?
What type of abx is streptomycin?
What type of abx is kanamycin?
What type of abx is neomycin?
What is the MOA of macrolides?
bind to the 50S ribosomal subunit
Are macrolides bacteriocidal or bacteriostatic?
What type of abx is clarithromycin?
What type of abx is azithromycin?
What type of abx is erythremycin?
What type of abx is dirithromycin?
What type of abx is roxithromycin?
What type of abx is telithroomycin?
When are macolides generally used?
When pt has an allergy to penicillin
What is the MOA of Quinolones?
inhibiting DNA gyrase (topoisomerase II) and/or topoisomerase IV activity of many Gram positive and Gram-negative bacteria
Are Quinolones bactericidal or bacteristatic?
What type of abx are nalidixic acid, ciprofloxacin and the newer fluoroquinolones, such as danofloxacin, difloxacin, enrofloxacin, marbofloxacin, and orbifloxacin.
What is the MOA of rifampin/rifabutin? Is this baceriocidal or bacteriostatic?
Binds to and inhibits RNA polBacteriocidal
What is the MOA of metronidazole? Is this bacteriocidal or bacterstatic?
Toxic compound to DNABactericidal
What are antimetabolites?
Abx that inhibit a part of bacterial metabolism
What type of abx are sulfonamides? What is the MOA?
Antimetabolite MOA = inhibits folate synthesis
What type of abx are DHFR inhibitors (trimethoprim)? What is the MOA?
Antimetabolite MOA = inhibits folate synthesis