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 invassi ve Streptococcus pyogenes infections has been reported in several countries . The objective of this study was to determine the clinical features of the se 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 blo od, sterile fluids or soft tissues. Patients' clinical records were reviewe d and bacterial isolates characterized. RESULTS. A total of 31 patients with invassive infections caused by S. pyog enes 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). T he mean age of patients was 41 years. Seventy four percent of patients had some underlying disease, and the most relevant conditions included: diabete s 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 pr esenting form was cellulitis (39%). Necrotizing fasciitis, septic shock, an d streptococcal toxic shock syndrome (STSS) were observed in 9.6%, 12.9%, a nd 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 b eing the most 29 common. CONCLUSIONS. A steady increase in the incidence of invassive infections cau sed by S. pyogenes was observed since 1995 to 1997 in our hospital. Patient s with certain underlying conditions are more susceptible to acquire these infections. The worst outcome of these infections corresponded to elderly p atients, those with septic shock or STSS. Most strains responsible for thes e infections were encapsulated and the M1 serotype predominated.