206. Variations in the frequency and impact of polymicrobial cultures in adults with invasive Group B Streptococcal (GBS) infection at the US Veterans Health Administration

Background GBS, a colonizer of human skin, genitourinary and gastrointestinal tracts, is responsible for increasing rates of invasive infection among non-pregnant adults in the United States. GBS is often isolated with other bacteria; however, the clinical significance of polymicrobial cultures in patients with invasive GBS infection is unknown. Our aim was to characterize polymicrobial cultures in patients with invasive GBS infection and explore their impact on mortality at 30 days. Methods Within the VHA Corporate Data Warehouse, we identified veterans active in VHA between 2008–2017 with invasive GBS infection according to CDC’s surveillance definitions. Reports of cultures from blood, bone and sterile fluid with GBS were assessed for the presence of other bacteria.We used International Classification of Disease (ICD) codes to define the type of invasive GBS infection. We compared 30-day all-cause mortality between patients with cultures that identified only GBS (monomicrobial cases) and patients with cultures that identified GBS and other bacteria (polymicrobial cases). Results Of 4780 incident cases of invasive GBS infection identified between 2008–2017, 1204 (25%) were polymicrobial. The proportion of polymicrobial cases varied by type of invasive GBS infection, ranging from 58% in osteomyelitis to 10–15%in meningitis, endocarditis, skin and soft-tissue infections, and septic arthritis (table). Staphylococcus aureuswas found in 516 (43%) of polymicrobial cases;there were variations in the bacteria isolated by type of infection (figure). Overall, there was no difference in 30-day mortality between polymicrobial and monomicrobial cases of invasive GBS infection (both 8%). However, when compared with monomicrobial cases, 30-day mortality was doubled in polymicrobial cases of pneumonia and bacteremia (15% vs. 31% and 11% vs. 22%, respectively). Conclusion The frequency, composition and mortality of polymicrobial cases vary according to the type of invasive GBS infection. Polymicrobial infection could be an important determinant of outcome in certain invasive GBS infections. The effect of polymicrobial infection involving GBS, relative to age, severity of illness and underlying comorbidities, needs further exploration. Disclosures All authors: No reported disclosures.