Antiobiotics I Flashcards
(47 cards)
What is the minimum inhibitory concentration? How is it visualized in a test tube? How about an E-strip test, smarty pants?
The minimum concentration of drug needed to slow/stop bacterial production.
Visualized as the tube with lowest concentration of drug WITHOUT turbidity in it.
With an E-strip test, the MIC is seen as the concentration where the line of growth intersects the filter paper.
What is the minimum bactericidal concentration? How is it visualized in the lab.
The minimum concentration of drug needed in tissue to kill bacteria.
Tubes without turbidity from MIC test are taken and cultured on separate agar plates. The plate that demonstrates no growth represents the concentration necessary for MBC.
What are the five antibiotic mechanisms of action we learned in class?
1) Inhibition of cell wall synthesis
2) Inhibition of protein synthesis
3) Inhibition of nucleic acid synthesis
4) Disruption of cell membranes
5) Anti-Mycobacterium agents (not exactly a mechanism but whatever, it’s in top points)
What group of antibiotics function by inhibiting transpeptidation?
Beta-lactams
Peptidoglycan is composed of a backbone of _____ & _____, crosslinked by _____
Backbone = N-acetylmuramic acid (NAM) & N-acetylglucosamine (NAG)
Crosslinking is by peptide chains
How do beta-lactams work on Gram (-) and Gram (+) bacteria?
Gram (-): Bind to and block enzyme that carries our transpeptidation between D-Ala and H2N-DAP
Gram (+): Prevents rxn between pentaglycine bridge and D-Ala
D-Ala involved in both instances!
What determines the activity, spectrum, pharmacologic properties and resistance of beta-lactams?
R groups
_____ is a bacterial enzyme that opens the beta-lactam ring via a hydrolysis rxn.
Beta-lactamase
T/F Penicillins are bacteriostatic
FALSE
Penicillins are bactericidal
What are the bacterial mechanisms of resistance to penicillins?
1) Alter affinity of transpeptidases to penicillins
2) Beta-lactamase production
3) Efflux pumps
4) Impermeable membranes (poor penetration)
Penicillins are widely distributed in tissues and secretions except _____, _____, and _____
CNS, prostatic fluid, and eye
T/F Penicillins are ineffective against intracellular pathogens
TRUE
What species are susceptible to Bacitracin?
1) G+ cocci/bacilli
2) Neisseria
3) H. influenza
4) T. pallidum
D-cycloserine is used as a ______. What is the characteristic side effect of an exceeded oral dose?
2nd line TB drug
Common neuropsychiatric side effects with exceeded oral dose
What species are resistant to Bacitracin?
1) Enterobacteriaceae
2) Pseudomonas
3) Nocardia
What are the four non-beta-lactam inhibitors of cell wall synthesis?
1) D-Cycloserine
2) Bacitracin
3) Vancomycin
4) Fosfomycin
T/F Bacitracin is commonly administered orally.
FALSE
Bacitracin is nephrotoxic, and is therefore ONLY used topically. Typically in a “triple antiobiotic” ointment with neomycin and polymyxin
What organisms are covered by Fosfomycin? Which are resistant?
Covers G+ & G- organisms (broad spectrum)
Anaerobes are resistant
What kind of infection is Fosfomycin typically used for?
Uncomplicated UTIs
What organisms does Vancomycin cover?
G+ ONLY (Narrow spectrum)
For what kind of infections is Vancomycin used?
1) MRSA/MRSE
2) C. diff
3) Enterococcus
4) G+ infections in pts. with penicillin allergy
T/F Organisms using D-Ala-D-Lac in their cell walls are good targets for Vancomycin
FALSE
Organisms using D-Ala-D-Lac in the cell walls are RESISTANT to Vancomycin (can’t bind D-Ala-D-Lac)
Vancomycin binds D-Ala-D-Ala
Penicillin is used for infections by _____ aerobes except for _____.
G+ aerobes EXCEPT Staph. (S. pneumo, S pyogenes, S. viridans endocarditis
Penicillin V covers G+ aerobes (except staph). What does penicillin G cover?
1) Anaerobes
- EXCEPT B. faecalis
2) Meningococcus
- NOT gonogoccus
3) Spirochete diseases
