Streptococcus intermedius is the most common streptococcus in soft tissue infections in injection drug users

Background: There have been reports of “Streptococcus milleri” group (now Streptococcus anginosus group) SAG, in soft tissue infections in iv drug users (IVDU). However, the significance of Streptococcus intermedius (SI) has not been reported. In our study of 1321 streptococcal isolates SI was the predominant Streptococcus in IVDU soft tissue infections. Other 2 members of the group, S constellatus (SC) and S anginosus (SA) were less frequent. Methods and materials: We studied 1321 Streptococcal isolates from different body sites admitted to our 10 network hospitals during a 3 year period ending in December 2019.There were 125 (9.5%) group A, 481 (36.4%) group B, 78 (5.9%) group C, 83 (6.3%) group G, 335 (25.4%) Streptococcus anginosus group (SAG) and 45 S gallolyticus and 174 others.There were 335 Streptococcus anginosus group (SAG) isolates from 167 males and 166 females, with ages ranging from 1 month to 90 years, consisting of 151 (84 M/67F) S anginosus, 107 (56 M/51F) SI and 77 (47 M/30/F) S constellatus (SC). We reviewed the clinical presentation, lab results, and susceptibilities of all streptococcal isolates. There were 32 drug users in patients culture positive for streptococci. Results: Streptococcal infections in 32 IV drug users were: 15 (46.9%) SI, 9 (28.1%) group A, 4 (12.5%) SA, 3 Streptococcus constellatus (9.4%), 1 each group C, group F, S dysgalactiae and alpha Streptococcus sp. There were no group B or G infections associated with IVDU. Majority were in the upper extremity 24/31 (77.4%), with 4/31 (12.9%) lower extremity, 1 pneumonia and 1 line infection. Other oral bacteria present in mixed infections were Prevotella oralis, P denticola, P intermedius, Eikenella corrodens, Haemophilus para influenzae and group C Streptococcus. Of 7 positive blood cultures in IVDU 5 were group A, one SI and 1 SC. Conclusion: SAG was common in soft tissue infections in IVDU with SI being the predominant Streptococcus. In IVDU with bacteremia, group A Streptococcus was the most common blood isolate. Mixed infections with other oral bacteria were often present. Group B and group G Streptococci were not isolated in IVDU in this study.