[Bacteremias due to the Streptococcus milleri group. An analysis of 18 episodes]

To study the epidemiological and clinical characteristics of bacteremia caused by Streptococcus milleri group streptococci (SMG).

Prospective evaluation of all bacteremic episodes with clinical significance from 1990 to 1995 in two general hospitals. In this study all episodes caused by SMG were analyzed.

A total of 905 bacteremic episodes with clinical significance were detected; 18 (1.98%) were caused by SMG (0.16/1,000 admissions). The mean age of patients were 43 years and the male/female ratio 1.6. Seventeen patients (94.4%) had some underlying disease; nine patients had diabetes, four were parenteral drug abusers, and two had neoplasms. The most common sources of bacteremia were intraabdominal in four episodes (two liver abscesses, one subphrenic abscess and one pancreatic pseudocyst), cutaneous and/or soft tissues in four, surgical wound in two and respiratory in two; no source was identified in five episodes. Four episodes had a polymicrobial origin. In 13 isolates the identification was at species level (Streptococcus anginosus eight, Streptococcus intermedius four and Streptococcus constellatus one). All strains were susceptible to penicillin. Six patients (33.3%) required surgery. In ten episodes a favorable outcome was recorded, although four patients required surgery. The infection associated mortality rate was 31.2%. The mean age of deceased patients was higher than for cured patients (62.2 +/- 20.2 versus 35.3 +/- 20.3; p < 0.05).

SMB bacteremia is uncommon. It involved mainly diabetic patients or parenteral drug abusers, commonly with an intraabdominal suppurative source or in skin or soft tissues. The mortality rate was high despite surgery in one third of patients. Patients with advanced age had a poorer prognosis. All isolates investigated were susceptible to penicillin.