[Invassive infections caused by Group A streptococci: clinical characteristics and microbiological analyses in 31 cases].

Background: In the last two decades an increase in the incidence of invassive Streptococcus pyogenes infections has been reported in several countries. The objective of this study was to determine the clinical features of these infections in our hospital.

Methods: Retrospective study (1995-1998) of patients admitted at Son Dureta Hospital, Palma de Mallorca, Spain, who had S. pyogenes recovered from blood, sterile fluids or soft tissues. Patients clinical records were reviewed and bacterial isolates characterized.

Results: A total of 31 patients with invassive infections caused by S. pyogenes were identified. The annual incidence rates (number of episodes/1,000 admissions) were: 0.13 (1995), 0.20 (1996), 0.27 (1997), and 0.23 (1998). The mean age of patients was 41 years. Seventy four percent of patients had some underlying disease, and the most relevant conditions included: diabetes mellitus (5), parenteral drug abuse (4), chronic alcoholism (3), chronic liver disease (3) and infection with the human immunodeficiency virus (3). The most common portal of entry was the skin (78%). The initial clinical presenting form was cellulitis (39%). Necrotizing fasciitis, septic shock, and streptococcal toxic shock syndrome (STSS) were observed in 9.6%, 12.9%, and 6.4% of patients, respectively. The mortality rate was 16.1%. The phenotypic characterization of S. pyogenes isolates indicated that most isolates were of mucoid type and identified 11 different M serotypes, M1 being the most common.

Conclusions: A steady increase in the incidence of invassive infections caused by S. pyogenes was observed since 1995 to 1997 in our hospital. Patients with certain underlying conditions are more susceptible to acquire these infections. The worst outcome of these infections corresponded to elderly patients, those with septic shock or STSS. Most strains responsible for these infections were encapsulated and the M1 serotype predominated.