Streptococcus anginosus group: Clinical significance of an important group of pathogens

The Streptococcus anginosus group was first discovered in the 1950s and over time has evolved to consist of three species designated S. anginosus, S. constellatus, and S. intermedius. Investigation of these bacteria over the last few decades has revealed that infections caused by these gram-positive cocci have significant variability in their clinical presentations. In addition, studies have shown that hemolysis, Lancefield group reaction, and other laboratory techniques commonly used to identify bacteria are inconsistent throughout the S. anginosus group. Clinical review has shown that while the S. anginosus group is found as normal flora in humans, these bacteria are pathogens associated with infection in multiple body sites. In addition, the S. anginosus group has been shown to be strongly associated with abscess formation, and recent studies have attempted to investigate the pathogenic mechanisms of these bacteria. While little antibiotic resistance has been noted, treatment of abscesses often requires surgical drainage.