Erythromycin is considered bacteriostatic at standard doses but becomes bactericidal against certain organisms at higher concentrations. Against which of the following is erythromycin reliably bactericidal at achievable serum concentrations?

• A Staphylococcus aureus (MSSA)
• B Pseudomonas aeruginosa
• C Haemophilus influenzae
• D Streptococcus pneumoniae ✓

Explanation

Macrolides are bactericidal at achievable concentrations against Streptococcus pneumoniae and group A streptococci, but bacteriostatic against S. aureus and H. influenzae. Pseudomonas aeruginosa is intrinsically resistant to macrolides due to efflux and poor outer membrane permeability, making option B clearly incorrect.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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