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]
What is the appropriate adjustment to drug administration if the trough is too high?
Decrease the frequency of the doses (increase the time interval between doses)
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
Why and when are perioperative antibiotics given?
They are given within 1 hour before incision to prevent surgical site infections.
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]
Which type of agent kills and inhibits organisms on inanimate objects?
Disinfectant
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]
What is the appropriate adjustment to drug administration if the peak is too high?
Decrease the amount of each dose
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]
Which type of agent kills and inhibits organisms on the body?
Antiseptic
What is the appropriate peak and trough level of Vancomycin?
- Peak 20-40 ug/mL
- Trough 5-10 ug/mL
What is the most common method of antibiotic resistance?
Transfer of plasmids
What is chlorhexidine gluconate (Hibiclens) effective against?
- Gram positive cocci
- Gram negative rods
- Fungi
