Bacteremia involving the "Streptococcus milleri" group: analysis of 19 cases.

During a 3-year study period, 19 patients at the University Hospital of Maastricht developed bloodstream infections with species of the "Streptococcus milleri" group, for an incidence of 0.33 per 1,000 admissions. The patients' median age was 48 years; the male-to-female ratio was 2.8. Eleven patients (57.9%) had underlying diseases, among which malignancy was predominant. Local trauma to the mucosal barrier was an important risk factor. An associated site of infection was found most frequently in the abdominal and thoracic cavities (nine and five cases, respectively). Bacteremia was polymicrobial in four of 19 episodes. The 20 infecting S. milleri strains were identified to the species level; Streptococcus anginosus was the most prevalent (16 strains). Eight strains carried Lancefield group C. The isolates were sensitive to most antibiotics. Abscess formation was documented in nine cases (47.3%); repeated drainage procedures were required in half of these episodes. Mortality was high (five of 19 patients, or 26.3%).