Which antibiotic class is intrinsically resistant in Enterococcus and should not be reported for susceptibility testing?

Which antibiotic class is intrinsically resistant in Enterococcus and should not be reported for susceptibility testing?

• A. Cephalosporins
• B. Aminoglycosides
• C. Macrolides
• D. Fluoroquinolones

Answer: (A)

Enterococcus species are intrinsically resistant to cephalosporins. This means their lack of activity against this class is built into their biology, not due to acquired resistance. The penicillin-binding proteins in Enterococcus have low affinity for cephalosporins, and the organism’s cell wall synthesis machinery isn’t effectively inhibited by this drug class, so cephalosporins don’t produce reliable, clinically meaningful results in susceptibility testing. Because this resistance is inherent, reporting cephalosporin susceptibility for Enterococcus would be misleading and unnecessary. Other antibiotic classes may have variable or context-dependent activity, but cephalosporins are avoided in susceptibility testing for Enterococcus.

Enterococcus species are intrinsically resistant to cephalosporins. This means their lack of activity against this class is built into their biology, not due to acquired resistance. The penicillin-binding proteins in Enterococcus have low affinity for cephalosporins, and the organism’s cell wall synthesis machinery isn’t effectively inhibited by this drug class, so cephalosporins don’t produce reliable, clinically meaningful results in susceptibility testing. Because this resistance is inherent, reporting cephalosporin susceptibility for Enterococcus would be misleading and unnecessary. Other antibiotic classes may have variable or context-dependent activity, but cephalosporins are avoided in susceptibility testing for Enterococcus.