Post-infectious glomerulonephritis commonly follows infection with which organism?

• A. Group A beta-hemolytic streptococcus
• B. Staphylococcus aureus
• C. E. coli
• D. Pseudomonas

Answer: (A)

Post-infectious glomerulonephritis is most classically seen after infection with nephritogenic strains of Streptococcus pyogenes, a group A beta-hemolytic streptococcus. The immune response to the infection forms circulating immune complexes that deposit in the glomeruli, activating complement and causing inflammation characteristic of immune-complex–mediated glomerulonephritis. This leads to edema, hypertension, and hematuria (often described as cola-colored urine) with RBC casts. The typical delay is about 1–3 weeks after a pharyngitis and a bit longer after skin infections like impetigo, which helps distinguish it clinically. Other bacteria can cause kidney issues, but the classic post-infectious nephritis most often follows group A Streptococcus infection.