A 65-year-old diabetic patient presents with fever, cough, and purulent sputum. His sputum Gram stain shows Gram-positive diplococci. The sputum culture grows alpha-haemolytic colonies on blood agar, bile-soluble, optochin-sensitive. The most likely pathogen and first-line outpatient treatment for mild CAP in a non-beta-lactam-allergic patient are:

• A Staphylococcus aureus — IV vancomycin
• B Klebsiella pneumoniae — oral cefuroxime
• C Streptococcus pyogenes — oral phenoxymethylpenicillin for 10 days
• D Streptococcus pneumoniae — amoxicillin 1 g 8-hourly orally for 5 days ✓

Explanation

Gram-positive diplococci that are optochin-sensitive, bile-soluble, and alpha-haemolytic on blood agar are Streptococcus pneumoniae (pneumococcus), the most common cause of community-acquired pneumonia worldwide. For mild CAP in a non-beta-lactam-allergic adult without recent antibiotic use, high-dose amoxicillin (1 g 8-hourly for 5 days) remains first-line per BTS and Indian guidelines. Macrolides (azithromycin) are added in atypical pneumonia suspicion. S. aureus is coagulase-positive and catalase-positive with golden pigment on culture.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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