A child with otitis media has had three ear infections in the ...

[schs14]

A child with otitis media has had three ear infections in the past year. The child has just completed a 10-day course of amoxicillin (Amoxil) with no improvement.
 
  The parent asks the nurse why this drug is not working, because it has worked in the past. What will the nurse tell the patient?
  a. Amoxicillin is too narrow in spectrum.
  b. The bacteria have developed a three-layer cell envelope.
  c. The bacteria have developed penicillin-binding proteins (PBPs) that have a low affinity for penicillins.
  d. The bacteria have synthesized penicillinase.

Question 2

A child with an ear infection is not responding to treatment with amoxicillin (Amoxil). The nurse will expect the provider to order:
 
  a. amoxicillinclavulan ic acid (Augmentin).
  b. ampicillin.
  c. nafcillin.
  d. penicillin G (Benzylpenicillin).

[ebe]

Answer to Question 1

ANS: D
Beta-lactamases are enzymes that cleave the beta-lactam ring and render the PCN inactive. This resistance is common with organisms that cause ear infections. Amoxicillin is a broad-spectrum antibiotic. A three-layer cell envelope occurs in gram-negative bacteria. Some bacterial strains, including methicillin-resistant Staphylococcus aureus (MRSA), develop PBPs with a low affinity for penicillins. MRSA is not a common cause of otitis media.

Answer to Question 2

ANS: A
Beta-lactamase inhibitors are drugs that inhibit bacterial beta-lactamases. These drugs are always given in combination with a penicillinase-sensitive penicillin. Augmentin contains amoxicillin and clavulanic acid and is often used when patients fail to respond to amoxicillin alone. Ampicillin is similar to amoxicillin, but amoxicillin is preferred and, if drug resistance occurs, ampicillin is equally ineffective. Pharmaceutical chemists have developed a group of penicillins that are resistant to inactivation by beta-lactamases (e.g., nafcillin), but these drugs are indicated only for penicillinase-producing strains of staphylococci. Penicillin G would be as ineffective as amoxicillin if beta-lactamase is present.

[schs14]

TYSM

[bblaney]

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