Invasive Infections Caused by Streptococcus pseudoporcinus: A Two-Case Series and Review of the Literature.

Streptococcus pseudoporcinus (S. pseudoporcinus) is a beta-hemolytic, Gram-positive, catalase-negative, nonmotile coccus that primarily colonizes the female genitourinary tract. Although it has historically been considered a colonizing organism, it has increasingly been associated with invasive infections. Its identification may be challenging because of its phenotypic similarity to other beta-hemolytic streptococci. We report two invasive infections caused by S. pseudoporcinus. The first occurred in a 59-year-old woman with cirrhosis who developed spontaneous bacterial peritonitis in the setting of chylous ascites. The second occurred in a 50-year-old woman who presented with pneumonia, hypoxemic respiratory failure, and a complicated parapneumonic effusion. S. pseudoporcinus was recovered from ascitic fluid and pleural fluid, respectively, and was identified using the VITEK 2 Compact (bioMérieux, Marcy-l'Étoile, France) system. Both patients received antimicrobial therapy and experienced favorable clinical outcomes without documented recurrence during follow-up. These cases expand the recognized clinical spectrum of invasive S. pseudoporcinus infection and emphasize the importance of accurate species-level identification of beta-hemolytic streptococci recovered from normally sterile sites.