A 62-year-old man with Enterococcus faecalis endocarditis is started on ampicillin plus gentamicin. The rationale for adding gentamicin to the cell-wall active agent is that the combination produces:

• A Prevention of emergence of aminoglycoside-modifying enzymes
• B Synergistic bactericidal killing by enhancing intracellular aminoglycoside uptake ✓
• C Additive ribosomal blockade at both 30S and 50S subunits
• D Suppression of the post-antibiotic effect, allowing shorter courses

Explanation

Enterococci are tolerant to cell-wall agents alone, which inhibit but do not kill. Aminoglycosides alone also fail because uptake is poor. A beta-lactam disrupts the cell wall, allowing gentamicin to enter and reach the 30S subunit, producing concentration-dependent synergistic bactericidal activity. This synergy underlies the standard ampicillin or penicillin plus gentamicin regimen for enterococcal endocarditis. The combination does not prevent enzymatic modification, and macrolides act on the 50S subunit, not alongside aminoglycosides here.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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