Antimicrobials Flashcards
Detail the mechanism of action of sulfonamides.
Inhibit folic acid synthesis
Compete with PABA for dihydropteroate synthase
Bacteriostatic
Detail the mechanism of action of fluoroquinolones.
Inhibit DNA gyrase
Bactericidal
Define an antimetabolite.
A drug, through chemical similarity, inhibits normal cellular metabolism
What compound do sulfonamides mimic?
PABA
What enzyme is inhibited by trimethoprim?
Dihydrofolate reductase
Define sequential blockade.
Combined action of 2 drugs that inhibit sequential steps in a pathway of bacterial metabolism
Is the combination of trimethoprim + sulfamethoxazole bactericidal or bacteriostatic?
Bactericidal
Trimethoprim-sulfamethoxazole is established to be effective against what opportunistic protozoal infection in an AIDS patient?
Toxoplasmosis
What drug class is effective at treating diarrhea caused by gram - pathogens?
Fluoroquinolones
List 3 fluoroquinolones.
Ciprofloxacin
Levofloxacin
Moxifloxacin
What compounds interfere with fluoroquinolone absorption?
Multivalent cations
What effect do fluroquinolones and aminoglycosides have on normal flora after the plasma concentration of the drug has fallen below the minimum inhibitory concentration?
Postantibiotic effects- continued inhibition of bacterial growth
What infections are fluroquinolones effective at treating?
Urogenital and GI tract infections due to gram negative organisms
What are the major antibiotics that inhibit bacterial wall synthesis?
Penicillins Cephalosporins Carbapenems Monobactams Vancomycin
Define bactericidal.
Kills bacteria
Define bacteriostatic.
Does not kill bacteria, but inhibits growth
What drug classes are considered beta-lactam antibiotics?
Penicillins
Cephalosporins
Carbapenems
Define beta-lactmases.
Bacterial enzymes that hydrolyze the beta-lactam ring of certain beta-lactam antibiotics
Define minimal inhibitory concentration.
Lowest concentration of a drug capable of inhibiting growth of an organism
Penicillins are polar compounds and are not metabolized extensively; usually, they are excreted in the urine via glomerular filtration and tubular secretion. What drug inhibits the latter process?
Probenecid- used to treat gout
Are beta-lactam antibiotics bactericidal or bacteriostatic?
Bactericidal
What are inhibitors of bacterial penicillinases?
Clavulanic acid
Sulbactam
Tazobactam
What is the mechanism of penicillin resistance responsible for MRSA and PRSP?
Structural changes in PBP
Which penicillin is administered parenterally? Which penicillin is administered orally?
Parenterally- Penicillin G
Orally- Penicillin V
Penicillin G is clinically useful in the treatment of infections caused by what organisms?
Common streptococci
Meningococci
Gram positive rods
Spirochetes
Is penicillin used to treat gonorrhea? Syphilis?
Gonorrhea- no
Syphilis- yes
What drugs have a wider spectrum of antibacterial activity than penicillin G, but remain susceptible to penicillinases?
Extended spectrum penicillins- Ampicillin, Amoxicillin
Antipseudomonal penicillins- Piperacillin (adds coverage for gram negatives)
What toxicities are associated with the penicillins?
Allergy
GI disturbances
Interstitial nephritis is associated with what penicillin?
Methicillin
What penicillin is associated with neutropenia?
Nafcillin
Penicillin can cause a rash and hemolytic anemia, contrast the hypersensitivity reactions associated with each.
Rash- type 1
Hemolytic anemia- type 2
Detail the mechanism of action of the cephalosporins.
Bind to PBPs- bactericidal
Are MRSA strains resistant to cephalosporins?
Yes
What are examples of first generation cephalosporins?
Cephalexin (po)
Cefazolin (parenteral)
What are examples of second generation cephalosporins?
Cefuroxime
Cefaclor
What are examples of third generation cephalosporins?
Ceftriaxone
Ceftazidime
Cefdinir
Cefepime
What are examples of fourth generation cephalosporins?
Cefepime
Ceftaroline
Sinus, ear, and respiratory infections caused by H. influenzae or M. catarrhalis can be treated with what class of drugs?
Second generation cephalosporins
What generation of cephalosporins have good penetration of the BBB?
Third
A patient has a history of anaphylaxis to penicillins, can they be treated with a cephalosporin?
No
What are examples of carbapenems?
Imipenem
Ertapenem
Why is cilastatin given with imipenem IV?
Inhibits dehydropeptidase- enzyme in kidney that degrades imipenem
Carbapenems are useful for what types of infections?
Infections caused by organisms resistant to other antibiotics
Where does vancomycin bind?
D-Ala-D-Ala terminal of bacterial wall peptidoglycan
What confers vancomycin resistance in strains of enterococci and staphylococci?
Replacement of terminal D-Ala by D-lactate
Bacitracin inhibits cell wall synthesis in gram-positive organisms, however, it is reserved for topical use, why?
Nephrotoxic
Daptomycin is active against vancomycin resistant strains of enterococci and staphylococci, why should creatine phosphokinase me monitored in a patient being treated with this drug?
Daptomycin can cause myopathy
A 33-year-old man was seen in a clinic with a complaint of dysuria and urethral discharge of yellow pus. He had a painless clean-based ulcer on the penis and nontender enlargement of the regional lymph nodes. Gram stain of the urethral exudate showed gram-negative diplococci within PMNs. What is the most appropriate treatment of gonorrhea in this patient?
Ceftriaxone IM as single dose
You want to start a patient with renal failure on imipenem, why must the dosing be adjusted for this patient?
Imipenem is hydrolyzed by renal dehydropeptidase, in the setting of renal failure toxic levels of the drug can cause CNS toxicity (seizures)
What is the mechanism by which pneumococci are resistant to penicillin G?
Changes in chemical structure of penicillin binding protein
