6: Antibiotics Flashcards
What is the appropriate peak and trough level of Gentamicin?
- Peak 6-10 ug/mL
- Trough Less than 1 ug/mL
What is the main side effect of Carbapenems such as Meropenem or Imipenem?
Seizures
Which antibiotics are effective against Enterococcus?
- Vancomycin
- Timentin/Zosyn
- Ampicillin/Amoxicillin
- Genatmicin + Ampicillin
Which bacteria do Aminoglycosides (Gentamicin, Tobramycin) treat?
- Gram negative rods
- Pseudomonas, Acinetobacter, and Serratia
- Not effective for anearobes
- Synergistic with Ampicillin for Enterococcus (Beta-lactams facilitate aminoglycoside penetration)
[Resistance due to modifying enzymes leading to decreased active transport. Side effects: reversible nephrotoxicity, irreversible ototoxicitiy]
Which class of antibiotics functions as a PABA analogue and inhibits purine synthesis?
Sulfonamides
[sulfonamide functions by competitively inhibiting enzymatic reactions involving para-aminobenzoic acid (PABA). PABA is needed in enzymatic reactions that produce folic acid, which acts as a coenzyme in the synthesis of purines and pyrimidines. Mammals do not synthesize their own folic acid so are unaffected by PABA inhibitors, which selectively kill bacteria]
Which bacteria do third-generation cephalosporins (IE Ceftriaxone, Ceftazidime, and Cefotaxime) treat?
- Gram negative rods (+/- anaerobic coverage)
- Pseudomonas, Acinetobacter, and Serratia
- Not effective for Enterococcus
[Side effects: cholestatic jaundice. Ceftriaxone is associated with sludging in the gallbladder]
Which bacteria do Ticarcillin and Pipercillin treat?
- Gram negative rods
- Pseudomonas, Acinetobacter, and Serratia
[Side effects: they inhibit platelets]
What is the mechanism of action of Echinocandins such as Anidulafungin (Eraxis)?
It inhibits synthesis of cell wall glucan
[This is the go-to drug for candidemia]
What is the mechanism of resistance of methicillin-resistant Staph Aureus (MRSA)?
Mutation of cell wall-binding protein
What is the mechanism of bacterial resistance to Penicillin?
Plasmid carrying gene for beta-lactamase
Which bacteria does the Streptogramin: Synercid (Quinupristin/Dalfopristin) treat?
Gram positive cocci (Including MRSA and VRE)
Which 5 antibiotics or classes of antibiotics work by inhibiting cell wall synthesis?
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams
- Vancomycin
What are Iodophors like Betadine effective against?
- Gram positive cocci
- Gram negative rods
[Poor against fungi]
What is the mechanism of action of Amphotericin?
Binds sterols in the wall and alters membrane permeability
[This is the go-to drug for fungal sepsis other than candida and aspergillus. Side effects: nephrotoxic, fever, hypokalemia, hypotension, anemia. Liposomal type has fewer side effects.]
What is the mechanism of action of Voriconazole and Itraconazole?
They inhibit ergosterol synthesis, which is needed for the cell membrane
[Voriconazole is the go-to drug for invasive aspergillosis. Itraconazole is the go-to drug for a patient on prolonged broad-spectrum antibiotics.]
What is the frequency of dosing of Zosyn?
QID dosing
Which infections are treated with Acyclovir and which are treated with Ganciclovir?
- Acyclovir: HSV, EBV
- Ganciclovir: CMV
What is the mechanism of action of Acyclovir?
It inhibits viral DNA polymerase
[Used for HSV and EBV infections]
Which bacteria do first-generation cephalosporins (IE Cefazolin and Cephalexin) treat?
- Gram positive cocci (Staph and Strep)
- Not effective for enterococcus
- Does not penetrate the CNS
[Ancef (Cefazolin) has the longest half-life, making it best for prophylaxis]
Which bacteria do Unasyn (Ampicillin/Sulbactam) and Augmentin (Amoxicillin/Clavulanic acid) specifically cover?
- Gram positive cocci (staph and strep)
- Gram negative rods
- +/- anaerobic coverage
- Enterococci
[Broad spectrum but is not effective for pseudomonas, acinetobacter, or serratia]
What is the side effect of Ethambutol?
Retrobulbar neuritis
Which 3 antibiotics or classes of antibiotics work by inhibiting the 50s ribosome and protein synthesis?
- Erythromycin
- Clindamycin
- Synercid
[Erythromycin is a macrolide. Synercid is a combination of Quinupristin and Dalfopristin, both of which are streptogramins]
Which class of antibiotic works by inhibiting DNA helicase (DNA gyrase)?
Quinolones
Which bacteria do second-generation cephalosporins (IE Cefoxitin, Cefotetan, and Cefuroxime) treat?
- Gram positive cocci (less staph activity)
- Gram negative rods (effective only for community-acquired GNRs)
- +/- anaerobic coverage
- Not effective for Enterococcus, Pseudomonas, Acinetobacter, or Serratia
[Cefotetan has longest half-life, making it best for prophylaxis]
Which bacteria do macrolides (Erythromycin) treat?
Gram positive cocci (best for community-acquired pneumonia and atypical pneumonias)
[Binds motilin receptor and is prokinetic for bowel. Side effects: Nausea, cholestasis]
What is the mechanism of action of Rifampin?
It inhibits RNA polymerase
[High rate of resistance. Side effects: hepatoxicity, GI symptoms]
Which bacteria does Tetracycline treat?
- Gram positive cocci
- Gram negative rods
- Syphilis
[Side effects: tooth discoloration in children]
What is the mechanism of resistance of Vancomycin-resistant enterococcus (VRE)?
Mutation in cell-wall binding protein
Which 3 antibiotics or classes of antibiotics work by inhibiting the 30s ribosome and protein synthesis?
- Tetracycline
- Aminoglycosides (Tobramycin, Gentamicin)
- Linezolid
Which antibiotic works by producing oxygen radicals that breakup DNA?
Metronidazole (Flagyl)
Which bacteria does Clindamycin treat?
- Anaerobes
- Some gram positive cocci
- Clostridium perfringens
[Good for aspiration pneumonia. Side effects: pseudomembranous colitis]
What is the mechanism of action of Isoniazid?
It inhibits mycolic acids
[Must be given with Pyridoxine. Side effects: hepatotoxicity, B6 deficiency]
Which 4 antibiotics are bacteriostatic?
- Tetracycline
- Clindamycin
- Erythromycin
- Bactrim
[Aminoglycosides have irreversible binding to ribosome and are considered bactericidal]
Which bacteria does Linezolid (Oxazolidinones) treat?
Gram positive cocci (including MRSA and VRE)
Which bacteria does Bactrim (Trimethoprim/Sulfamethoxazole) treat?
- Gram negative rods
- +/- Gram positive cocci
- Not effective for Enterococcus, Pseudomonas, Acinetobacter, and Serratia
[Side effects: teratogenic, allergic reactions, renal damage, Stevens-Johnson syndrome (erythema multiforme), hemolysis in G6PD-deficient patients]
What is the difference between the coverage of Ampicillin and the coverage of penicillin?
Ampicillin has the coverage of penicillin plus coverage of enterococci
[Penicillin covers gram positive cocci, beta-hemolytic Streptococcus, syphilis, Neisseria meningitides (GPR), Clostridium perfringens (GPR), and anthrax.]
Which bacteria does Monobactam (Aztreonam) treat?
- Gram negative rods
- Pseudomonas, Acinetobacter, and Serratia
Which antibiotic works by inhibiting RNA polymerase?
Rifampin
Which antibiotics are effective against Pseudomonas, Acinetobacter, and Serratia?
- Ticarcillin/Piperacillin
- Timentin/Zosyn
- 3rd-generation Cephalosporins
- Aminoglycosides (Gentamicin and Tobramycin)
- Meropenem/Imipenem
- Fluoroquinolones
[Pseudomonas should be double covered]
Which bacteria do Oxacillin and nafcillin specifically treat?
Staphylococcus only
[Anti-staph penicillins]
What is the mechanism of action of Ganciclovir?
It inhibits viral DNA polymerase
[Used for CMV infections. Side effects: decreased bone marrow, CNS toxicity.]
Which bacteria do Timentin (Ticarcillin/Clavulanic acid) and Zosyn (Piperacillin/Sulbactam) treat??
- Gram positive cocci
- Gram negative rods
- Anaerobes
- Enterococci, Pseudomonas, Acinetobacter, and Serratia
[Side effects: they inhibit platelets]
What is the mechanism of bacterial resistance to Gentamicin?
Modifying enzymes that lead to a decrease in active transport of gentamicin into the bacteria
Which bacteria does Metronidazole (Flagyl) treat?
Anaerobes
[Side effects: Disulfuram-like reaction, peripheral neuropathy (long-term use)]
Which antibiotic inhibits dihydrofolate reductase, which inhibits purine synthesis?
Trimethoprim
Which bacteria do Penicillins specifically treat?
- Gram positive cocci (beta-hemolytic strep)
- Syphilis (Treponema pallidum - Spirochete)
- Neisseria meningitides (GPR)
- Clostridium perfringens (GPR)
- Anthrax (Bacillus anthracis - GPR)
[Not effective against staphylococcus or enterococcus]
Which bacteria do Quinolones (Ciprofloxacin, Levofloxacin, Norfloxacin) treat?
- Some gram positive cocci
- Pseudomonas, Acinetobacter, and Serratia
- Not effective for Enterococcus
- 40% of MRSA is sensitive (same efficay PO and IV)
[Ciprofloxacin has BID dosing. Levofloxacin has QD dosing]
Which bacteria do Carbapenems (Meropenem, Imipenem) treat?
- Gram positive cocci
- Gram negative rods
- Anaerobes
- Not effective for MEP (MRSA, Enterococcus, and Proteus)
[Must be given with Cilastatin to prevent renal hydrolysis of the drug, thus increasing its half-life. Side effects: Seizures]
Which bacteria does Vancomycin treat?
- Gram positive cocci (including MRSA)
- Enterococcus
- Clostridium Difficile
[Binds cell wall proteins. Resistance develops from a change in cell wall-binding protein. Side effects: HTN, Redman syndrome (histamine release), nephrotoxicity, ototoxicity]
What is chlorhexidine gluconate (Hibiclens) effective against?
- Gram positive cocci
- Gram negative rods
- Fungi
