EXAM #4: ANTIBIOTICS III Flashcards
What class of antibiotic is Clindamycin?
Protein synthesis inhibitor
What is the spectrum of specificity of Clindamycin?
Narrow–commonly used to treat strep and staph soft tissue infections
What is the MOA of Clindamycin?
- Blocks the 50S subunit
- Step 1 (A site)
- Also blocks translocation of the amino acid chain to the P site
What are the key adverse effects associated with Clindamycin?
GI disturbances esp. C. DIFF
What class of antibiotic is Chloramphenicol?
Protein synthesis inhibitor
What is the MOA of Chloramphenicol?
- Binds the 50S subunit
- Prevents peptide bond formation
What are the key adverse effects seen with Chloramphenicol?
1) Suppression of RBC production
2) Gray Baby Syndrome
What is Gray Baby Syndrome?
- Serious side effect of IV chloramphenicol administration in newborn
- Infants have immature UGT
- UGT is needed to metabolize the drug–concentrations become toxic
What is Cloramphenicol typically used to treat?
Serious infections such as Typhus and Rocky Mountain Spotted Fever
What are the three drugs used to treat “resistant” organisms?
Vancomycin
Linezolid
Daptomycin
What class of drug is Linezolid?
Protein Synthesis Inhibitor
What is the specificty of Linezolid?
Gram positive organisms
What is the MOA of Linezolid?
- Binds 50S subunit
- Binds the A-site
What is the key adverse effect associated with Linezolid?
Myelosuppression
What is the general pattern of specificity regarding the protein synthesis inhibitors?
Broad spectrum
What protein synthesis inhibitor is NOT broad spectrum?
Clindamycin
What antibiotic class do the Sulfonamides fall into?
DNA synthesis inhibitors
List the Sulfonamides.
Sulfadizine
Sulfamethoxazole
Sulfamethizole
What do you need to remember about the Sulfonamides?
Commonly used in conjunction with another class of antibiotics
What is the MOA of the Sulfonamides?
- Structurally, these drugs are similar to PABA
- Compete with endogenous PABA in DNA synthesis
- Prevent DNA synthesis
What are the key adverse effects seen with the Sulfonamides?
1) Hypersensitivity
2) Photosensitivty
3) Steven-Johnson Syndrome
Think S-Skin
What type of infections are the Sulfonamides commonly used to treat?
UTIs
What is the specificity of the Sulfonamides?
Broad
What general class of antibiotic are the Trimethoprims?
DNA synthesis inhibitor
What two drugs fall into the category of Trimethoprims?
Trimethoprim
Pyrimethamine
What is the spectrum of activity for Trimethoprim?
Gram negative bacteria
What is Trimethoprim commonly used to treat?
UTIs
What is the MOA of Trimethoprim?
Inhibitor of bacterial dihydrofolate reductase i.e. DNA synthesis inhibitor
What is the key adverse effect associated with Trimethoprim?
Bone marrow suppression
Megaloblastic anemia
How are Sulfamethoxazole and Trimethoprim commonly administered?
Together as TMP-SMX i.e. Bactrim
What is TMP-SMX commonly given for?
UTI and Prostatitis
What class of antibiotics do the Fluoroquinolones fall into?
DNA sythesis inhibitors
What drugs are Fluoroquinolones?
Norfloxacin Ciprofloxacin Levofloxacin Ofloxacin Gatifloxacin Gemifloxacin Moxifloaxcin
What is the specificity of the Fluoroquinolones?
Broad (gram positive and negative)
What is the MOA of the Fluoroquinolones?
Inhibition of Topoisomerase to disrupt the unwinding of DNA
What are the key adverse effects seen with the Fluoroquinolones?
1) GI disturbances
2) Bind divalent cations e.g. Ca++ and prevent absorptions
3) QT prolongation
What is the Group 1 Fluoroquinolones?
Norfloaxacin
What are the Group 2 Fluoroquinolones?
Ciprofloxacin
Levofloxacin
Ofloxacin
What type of organisms are best targeted by the group 2 Fluoroquinolones?
Gram negative
What are the Group 3 Fluoroquinolones?
Gatifloxacin
Gemifloxacin
Moxifloaxacin
What bacteria are best targeted by the Group 3 Fluoroquinolones?
Gram positive
What is the mechanism of action of Metronidazole?
Induction of DNA damage
What types of organisms can be treated with Metronidazole?
BOTH bacteria AND protozoa
What is unique about Metronidazole?
Pro-drug that must undergo reduction
What bacteria is Metronidazole used to treat?
Anaerobic bacteria b/c they contain the enzyme necessary for reduction i.e. activation
What is Metronidazole commonly used to treat?
C.diff –along with Vancomycin
What are the key adverse effects of Metronidazole?
1) GI disturbances
2) Disulfiram-effect; thus, patients should avoid alcohol on this drug
What the the MOA of Daptomycin?
- Binds to the membrane of the bacteria
- Forms a pore and causes membrane depolarization
*This is a bactericidal
What is the specificity of Daptomycin?
Similar to Vancomycin–useful against Gram positive organisms
What key adverse effect is associated with Daptoymcin?
MSK disturbances i.e.
1) Rhabdomyolysis
2) Mypoathy
What is the MOA of Polymyxin B?
Detergent that punches holes in the membrane structure
What is Polymyxin B specific for?
LPS i.e. it is used to treat Gram negative bacteria
How is Polymyxin B commonly used?
Topically, similar to Bacitracin
What mechanisms of resistance are associated with PCNs and Cephalosporins?
1) Beta-Lactamase
2) Alteration of the PBP binding to drug
2) Alteration in porin function
What mechanisms of resistance are associated with Aminoglycosides?
Expression of enzymes that alter the structure of the drug
What mechanisms of resistance are associated with Macrolides?
1) Drug efflux pump
2) Alteration in binding to the 50S subunit
What mechanisms of resistance are associated with Tetracyclines?
Drug efflux pump
What mechanisms of resistance are associated with Sulfonamides?
1) Less sensitive drug target (isozyme)
2) Increased synthesis of PABA
3) Use of alternate sources of folic acid
What mechanisms of resistance are associated with Fluoroquinolones?
1) Less sensitive drug target
2) Drug efflux pump
What mechanisms of resistance are associated with Chloramphenicol?
Expression of inactivating enzymes
