Antiobiotics I Flashcards
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
Oxacillin, cloxacillin, dicloxacillin and nafcillin are all examples of _____ penicllins
Isoxazolyl penicillins
T/F Isoxazolyl penicillins cover MRSA
FALSE
MRSA is resistant to Isoxazolyl penicillins
Ampicillin and amoxicillin are examples of _____ penicillins
Aminopenicillins
Aminopenicillins, broad spectrum abx, are typically ineffective against beta-lactamase positive organisms. What is administered to patients to allow aminopenicillins to work against these organisms?
Beta-lactamase inhibitors.
These effectively increase the spectrum of aminopenicillins.
What kinds of infections are aminopenicillins used for (5)?
1) URI
2) Otitis media (H. influenza)
3) Uncomplicated UTI (E. Coli)
4) Acute meningitis (kids)
5) Typhoid fever (salmonella)
What type of penicillin is used as an anti-pseudomonas drug?
Carboxypenicillin/Ureidopenicillin
Ticarcillin is the specific drug. Above is the lass.
When combined, what anti-pseudomoal penicillins have the broadest spectrum? What is the trade name of this combination?
Piperacillin (ureidopen.) + Tazobactam
Trade name = zosyn
T/F The action/resistace of cephalosporins are essentially the same as penicillins
TRUE
Cefazolin, cefuroime and cephadroxil are all _____ cephalosporins
First generation
First generation cephalosporins work excellently against susceptible _____ & _____. They are used for _____/_____ infections.
First generation cephalosporins work excellently against susceptible STAPH & STREP. They are used for SKIN/SOFT TISSUE infections.
Cefaclor, cefuroxime, and cefprozil are all _____ cephalosporins
Second generation
Second generation cephalosporins have _____ activity against G+ organisms, and _____ on G- organisms and anaerobes
Modest activity against G+
Increased activity against G- and anaerobes
What are second generation cephalosporins used to treat?
POLYMICROBIAL INFECTIONS!
1) Diabetic foot ulcers
2) PID
3) Respiratory tract infections (upper and lower)
4) Intraabdominal infections
Ceftriaxone, cefotaxime, cefoperazone, and cefpodoxime are the _____ cephalosporins
Third generation cephalosporins
_____ cephalosporins are the drug of choice for severe infections
Third generation cephalosporins
What organisms are resistant to third generation cephalosporins?
1) Listeria
2) B-lactamase positive Pneumococci
Third generation cephalosporins are broad spectrum abx that are the drug of choice or serious infections. Which infections are specifically included in their coverage?
1) G- sepsis
2) Lyme disease
3) Bacterial meningitis (Ceftriaxone)
- EXCEPT Listeria and Pneumococci w/beta-lactamase
The only fourth generation cephalosporin is _____
Cefepime
Cefepime (a fourth generation cephalosporin) has the same antimicrobial spectrum as third generation cephalosporins, but resists more _____. It is good for _____ infections.
Resists more beta-lactamases
Good for nosocomial infections
The only fifth generation cephalosporin is _____
Ceftaroline
T/F Ceftaroline (5th gen) has the same spectrum as Cefepime (4th gen.), but works better against P. aerguinosa.
FALSE
Ceftaroline does NOT cover Pseudomonas
Imipinem is a carbapenem that is _____ spectrum. It covers _____ and _____
Broad spectrum
Covers anaerobes and Pseudomonas
Aztreonam is a monobactam that is _____ spectrum. It covers ONLY _____ including _____
Narrow spectrum
Covers only G- AEROBES including Pseudomonas