ABSTRACT
Throughout 1996, 22 hospital-based laboratories in the Rhône-Alpes region of France collected pneumococcal strains and used a standardized protocol to record the following data; patient age and sex; type of specimen; and determination of susceptibility to at least the following antibiotics: oxacillin 1 microgram and 5 micrograms, erythromycin (Ery), tetracycline (Tet), chloramphenicol (Chl), rifampin (Rmp), and loracarbef. For penicillin-nonsusceptible strains (PNSSs), which were identified based on results with oxacillin, MICs for penicillin G, amoxicillin (Amx), and cefotaxime (Ctx) were determined using the E Test, at the study site and agar dilution at the coordinating center. Of the 1153 strains, 65.5% were from adults and 31.8% from children; patient age was unknown in 2.7% of cases. PNSPs (MIC > 0.06 mg/l) contributed 32.9% of strains (I: 23.3%; R: 9.6%) and were more common in children (41.1%) than in adults (28.1%). The frequency of PNSSs varied across specimen types: 27.9% in blood cultures (305 strains), 15.6% in cerebrospinal fluid (32), 38.7% in protected bronchopulmonary specimens (31), 31.5% in unprotected bronchopulmonary specimens (434), 50.8% in acute otitis media (118), and 34.4% in other specimens (221). Among PNSSs, nonsusceptibility (I + R) to other antibiotics was variable: Ery, 62.1%; Tet, 41.5%; Chl, 40.4%; Rmp, 1.1%. Corresponding figures for the overall strain population were Ery, 33.3%; Tet, 22.7%; Chl, 22.8%; Rmp, 0.9%. In addition, 56.5% of PNSSs exhibited multiple drug resistance. Resistance to amoxicillin (MIC > 2 mg/l) was demonstrated for only 5 strains. No strains were resistant to loracarbef or cefotaxime. Serotypes of the 379 PNSSs were as follows: 23F, 26.6%; 14 (25.6%); 9V (18.2%), 6 (8.7%), 15 (5%), 19 (4.5%).
Subject(s)
Anti-Bacterial Agents/pharmacology , Microbial Sensitivity Tests/standards , Pneumococcal Infections/drug therapy , Pneumococcal Infections/microbiology , Streptococcus pneumoniae/classification , Adult , Child , Drug Resistance, Microbial , Drug Resistance, Multiple , Female , France , Humans , Laboratories/standards , Male , Quality Assurance, Health Care , Specimen Handling/methods , Streptococcus pneumoniae/drug effects , Streptococcus pneumoniae/isolation & purificationABSTRACT
In 1996-1997 a multicentre study was carried out on 450 Streptococcus pneumoniae strains to compare the MICs and susceptibility categories obtained with the Etest (AB Biodisk) used under routine conditions in 22 hospital laboratories in the Rhône-Alpes region, France, with those obtained by the reference technique of agar dilution performed in a single coordinating centre. Each laboratory detected penicillin resistant pneumococci (PRP) by the oxacillin disk method (1 microgram and 5 micrograms) and determined the MICs of penicillin G (PG), amoxycillin (AMX) and cefotaxime (CTX) by the Etest. All the PRP strains were collected in the coordinating centre where MICs were carried out. The strains were classified as susceptible (S), intermediate (I) and resistant (R) according to the CASFM criteria (Comité de l'Antibiogramme de la Société Française de Microbiologie). The concordance results based on susceptibility categories are as follows: PG = 67.6%, AMX = 63.6%, CTX = 71.5%. Minor errors are as follows: PG = 31.2%, AMX = 36%, CTX = 28.5%. Major and very major errors are rare (0% to 0.6%). Agreement within 1 log2 dilution was obtained for about 80% of the strains. The minor errors results from strains clustering near the breakpoints 1 mg/l (PG) and 0.5 mg/l (AMX, CTX), and from practical difficulties in routine use of the Etest. These discrepancies may result in severe therapeutic problems. This study confirms the limits of the Etest. The authors insist on standardization and rigorous use of the Etest under routine conditions.