Group A streptococcal bacteremia: outcome and prognostic factors

In the last two decades, an increase in the incidence of invasive group A streptococcus (GAS) infections has been reported. The aim of this study was to determine the clinical and epidemiological characteristics and the natural history of GAS bacteremias at our hospital by performing a retrospective study of all cases of GAS bacteremia diagnosed at our University hospital from 1994 to 2003. We reported 42 cases of GAS bacteremia (27 men, mean age 42.3 +/- 31.6 years). None had more than one episode and four cases were nosocomial. The mean annual incidence rate was 1.01 cases per 100,000 population. An increase in the incidence but not in severity of GAS bacteremia was observed in the last 5-year period (p<0.001). The rates were highest in young children and the elderly and those with underlying medical conditions; 73.8% of patients had some underlying chronic illness, and the most relevant conditions included peripheral vascular disease and diabetes mellitus. Mortality was high and the worst outcome corresponded to elderly patients with streptococcal toxic shock syndrome (STSS). Thirty patients (71.4%) had a disruption in the integrity of the skin barrier, 14 (33.3%) were immunocompromised patients and 6 patients (14.3%) were intravenous drug users. A source of the bacteremia was noted in 38 patients (90.5%), with skin and soft tissue infection being the major portals of entry. Twelve patients (28.6%) fulfilled the STSS criteria. All strains were susceptible to penicillin and vancomycin. Resistance to erythromycin was 21.4% and to ciprofloxacin was 17.5%. The global mortality rate was 28.6%. Only STSS was significantly associated with increased mortality in the multivariate analysis.