Streptococcus pneumoniae is an important pathogen responsible for serious invasive diseases, including meningitis and septicemia. The spread of multidrug-resistant (MDR) pneumococci has become a worldwide problem, making treatment more difficult (18). Indeed, in addition to resistance to penicillin, resistance to other antibiotics, including erythromycin, tetracycline, and chloramphenicol, has emerged and is spreading (10).Since 1989, the National Institute of Health Dr. Ricardo Jorge reference laboratory has been continually monitoring the in vitro activity of antimicrobial agents against S. pneumoniae collected from invasive sources. This program for monitoring susceptibility to antibiotics in Portugal (ARSIP) provides a unique collection of Portuguese pneumococcal isolates. This national surveillance study reported that 4.6% of isolates were penicillin nonsusceptible in 1989, and this value remained generally stable until 1991 (6.4%) (32). Fully penicillin-resistant isolates (MIC of 2 g/ml) were reported for the first time in 1992 (0.8%) and made up 5.5% of isolates in the following year (32).Here, we describe the surveillance of pneumococci by the reference laboratory in Portugal. We report the in vitro activities of different antimicrobial agents used against S. pneumoniae isolated from invasive sources over 11 years (from 1994 to 2004).
MATERIALS AND METHODSPatients and bacterial isolates. Between 1 January 1994 and 31 December 2004, the ARSIP survey conducted by the Antibiotic Resistance Unit (ARU) from the National Institute of Health Dr. Ricardo Jorge constantly monitored pneumococcal isolates from cases of invasive disease in various regions of Portugal. The national laboratory-based surveillance system collected 1,331 invasive pneumococcal strains, which were isolated in 24 bacteriology laboratories in hospitals and public health institutions. In the period 1994 to 1998, 12 hospitals participated in the study, and since 1999, 12 more hospitals have been added to the network. Isolates were included if they were nonrepetitive or consecutive blood, cerebrospinal fluid (CSF), or pleural fluid samples from patients with symptoms compatible with invasive pneumococcal disease. No changes were made to the methods of data collection during the study. Some isolates were from outpatients, but most were from patients hospitalized with communityacquired invasive pneumococci disease. Only one isolate per patient was considered. Patients over 15 years old were considered to be adults.Identification and serotyping. The isolates were sent at Ϫ20°C by hospital laboratories to the reference laboratory, ARU, in Trypticase soy broth (TSB; Oxoid, Basingstoke, England) containing 20% glycerol. On reception by the ARU, the purity of the pneumococcal isolate was checked using standard methods, and the isolate was then stored at Ϫ80°C in TSB containing 20% glycerol. Isolates were serotyped by dot blotting, the Quellung reaction, or both (11).Antimicrobial susceptibility testing. Susceptibility testing was performed by the aga...
