A 27-year-old pregnant woman at 36 weeks gestation is screened during prenatal care. A vaginal swab is cultured in Tod-Hewitt broth. Gram stain shows Gram-positive cocci in chains. Blood agar shows gray colonies with narrow beta-hemolysis. CAMP test shows arrow-shaped hemolysis near Staphylococcus aureus. Hippurate hydrolysis is blue. Which organism is suspected?

Prepare for the CAMLPR Microbiology Test. Utilize flashcards and engaging multiple-choice questions, each equipped with descriptions and explanations. Ready yourself for an excellent performance!

Detecting Group B Streptococcus carriage in late pregnancy relies on a combination of lab traits that distinguish this organism from other streptococci. The Gram-positive cocci in chains fit a streptococcus, and the narrow beta-hemolysis on blood agar is compatible with group B strep, but the decisive clues are the CAMP test and hippurate reaction. The arrowhead (arrow-shaped) hemolysis that forms near Staphylococcus aureus is the classic CAMP test result for Streptococcus agalactiae, because its CAMP factor enhances the beta-hemolysin of S. aureus. The blue color from hippurate hydrolysis confirms hippurate-positive organisms, which includes Streptococcus agalactiae. Tod-Hewitt broth enrichment is routinely used to improve recovery of this organism from vaginal/rectal swabs in prenatal screening. Taken together, these findings point to Streptococcus agalactiae, the organism routinely screened for in pregnancy to prevent neonatal infection.