Differentiating Streptococcus pseudoporcinus from GBS: could this have implications in pregnancy?

Background: Streptococcus agalactiae (GBS) is a common pathogen known to cause neonatal and maternal infectious morbidity. Streptococcus pseudoporcinus (S pseudoporcinus) is a separate, recently identified β-hemolytic gram-positive coccus that can cause false-positive results on standard GBS agglutination testing assays. Objective: To determine the prevalence and clinical implications of Streptococcus pseudoporcinus colonization in pregnancy. Materials and Methods: This is a 2-year retrospective cohort study comparing pregnant women colonized with GBS to those colonized with S. pseudoporcinus. A proteomics method of identification, namely, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, was used to distinguish between S. pseudoporcinus and GBS colonization. Antibiotic susceptibility testing was carried out on all specimens. Maternal and neonatal chart reviews were conducted to identify predictors of S. pseudoporcinus colonization and to compare maternal and neonatal outcomes. Results: S. pseudoporcinus colonization occurred in 1.6% of all pregnancies. A total of 2.5% of all GBS-positive results by agglutination assay were false positive, instead reflecting S. pseudoporcinus colonization. Clindamycin resistance among S. pseudoporcinus isolates is uncommon. S. pseudoporcinus colonization in pregnancy is independently associated with African American race, tobacco use, and body mass index ≥35. Preterm premature rupture of membranes or spontaneous preterm birth was more common in patients colonized with S. pseudoporcinus. Conclusion: Although the prevalence of S. pseudoporcinus colonization is low, it primarily occurs in African American women and is associated with preterm premature rupture of membranes or spontaneous preterm birth when compared to individuals colonized with GBS.