Validation of the BacT/ALERT®3D automated culture system for the detection of microbial contamination of epithelial cell culture medium.

Living tissue engineering for regenerative therapy cannot withstand the usual pharmacopoeia methods of purification and terminal sterilization. Consequently, these products must be manufactured under aseptic conditions at microbiologically controlled environment facilities. This study was proposed to validate BacT/ALERT(®)3D automated culture system for microbiological control of epithelial cell culture medium (ECCM). Suspensions of the nine microorganisms recommended by the European Pharmacopoeia (Chap. 2.6.27: "Microbiological control of cellular products"), plus one species from oral mucosa and two negative controls with no microorganisms were prepared in ECCM. They were inoculated in FA (anaerobic) and SN (aerobic) culture bottles (Biomérieux, Lyon, France) and incubated in a BacT/ALERT(®)3D automated culture system. For each species, five sets of bottles were inoculated for reproducibility testing: one sample was incubated at the French Health Products Agency laboratory (reference) and the four others at Cell and Tissue Bank of Lyon, France. The specificity of the positive culture bottles was verified by Gram staining and then subcultured to identify the microorganism grown. The BacT/ALERT(®)3D system detected all the inoculated microorganisms in less than 2 days except Propionibacterium acnes which was detected in 3 days. In conclusion, this study demonstrates that the BacT/ALERT(®)3D system can detect both aerobic and anaerobic bacterial and fungal contamination of an epithelial cell culture medium consistent with the European Pharmacopoeia chapter 2.6.27 recommendations. It showed the specificity, sensitivity, and precision of the BacT/ALERT(®)3D method, since all the microorganisms seeded were detected in both sites and the uncontaminated medium ECCM remained negative at 7 days.

Utility of the Etest GRD for detecting Staphylococcus aureus with reduced susceptibility to glycopeptides in cystic fibrosis patients.

Glycopeptide-intermediate S. aureus (GISA), particularly heterogeneous GISA (hGISA), remain difficult to detect in the routine practice of medical microbiology. Novel tools have been evaluated comparatively to the population analysis profile-area under the curve (PAP-AUC) reference method for detecting GISA/hGISA. Among them, the Etest GRD showed relatively high specificity (85.8-97%) and negative predictive value (97%) but lower sensibility (57-95%) and positive predictive value (30.8%). We investigated the utility of the Etest GRD for detecting GISA/hGISA among 180 strains isolated from 106 cystic fibrosis (CF) patients. Etest GRD was performed on all isolates, and those exhibiting a GISA/hGISA phenotype were further tested by PAP-AUC and other agar routine assays for GISA/hGISA detection. The Etest GRD allowed the detection of 15 GISA/hGISA strains, of which eight were confirmed by the reference method. Despite the 3.9% level of false positive results, the Etest GRD constitutes a useful routine tool for detecting GISA/hGISA overlooked by other routine assays, two strains being detected by the Etest GRD only. GISA/hGISA represented 7.7% of MRSA and 2.1% of MSSA, and were found in 4.7% of CF patients colonized/infected by S. aureus, which is the highest rate reported to date in this population.

In vitro antibacterial activity of ceftobiprole against clinical isolates from French teaching hospitals: proposition of zone diameter breakpoints.

The aims of this study were to determine the in vitro activity profile of ceftobiprole, a pyrrolidinone cephalosporin, against a large number of bacterial pathogens and to propose zone diameter breakpoints for clinical categorisation according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) minimum inhibitory concentration (MIC) breakpoints. MICs of ceftobiprole were determined by broth microdilution against 1548 clinical isolates collected in eight French hospitals. Disk diffusion testing was performed using 30 µg disks according to the method of the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM). The in vitro activity of ceftobiprole, expressed by MIC(50/90) (MICs for 50% and 90% of the organisms, respectively) (mg/L), was as follows: meticillin-susceptible Staphylococcus aureus, 0.25/0.5; meticillin-resistant S. aureus (MRSA), 1/2; meticillin-susceptible coagulase-negative staphylococci (CoNS), 0.12/0.5; meticillin-resistant CoNS, 1/2; penicillin-susceptible Streptococcus pneumoniae, ≤ 0.008/0.03; penicillin-resistant S. pneumoniae, 0.12/0.5; viridans group streptococci, 0.03/0.12; ß-haemolytic streptococci, ≤ 0.008/0.016; Enterococcus faecalis, 0.25/1; Enterococcus faecium, 64/128; Enterobacteriaceae, 0.06/32; Pseudomonas aeruginosa, 4/16; Acinetobacter baumannii, 0.5/64; Haemophilus influenzae, 0.03/0.12; and Moraxella catarrhalis, 0.25/0.5. According to the regression curve, zone diameter breakpoints could be 28, 26, 24 and 22 mm for MICs of 0.5, 1, 2 and 4 mg/L respectively. In conclusion, this study confirms the potent in vitro activity of ceftobiprole against many Gram-positive bacteria, including MRSA but not E. faecium, whilst maintaining a Gram-negative spectrum similar to the advanced-generation cephalosporins such as cefepime. Thus ceftobiprole appears to be well suited for the empirical treatment of a variety of healthcare-associated infections.

In vitro antibacterial activity of doripenem against clinical isolates from French teaching hospitals: proposition of zone diameter breakpoints.

The aims of the study were to determine the in vitro activity of doripenem, a new carbapenem, against a large number of bacterial pathogens and to propose zone diameter breakpoints for clinical categorization in France according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) minimum inhibitory concentration (MIC) breakpoints. The MICs of doripenem were determined by the broth microdilution method against 1,547 clinical isolates from eight French hospitals. The disk diffusion test was performed (10-µg discs) according to the Comité de l'Antibiogramme de la Société Française de Microbiologie (CASFM) method. The MIC(50/90) (mg/L) values were as follows: methicillin-susceptible Staphylococcus aureus (MSSA) (0.03/0.25), methicillin-resistant Staphylococcus aureus (MRSA) (1/2), methicillin-susceptible coagulase-negative staphylococci (MSCoNS) (0.03/0.12), methicillin-resistant coagulase-negative staphylococci (MRCoNS) (2/8), Streptococcus pneumoniae (0.016/0.25), viridans group streptococci (0.016/2), ß-hemolytic streptococci (≤0.008/≤0.008), Enterococcus faecalis (2/4), Enterococcus faecium (128/>128), Enterobacteriaceae (0.06/0.25), Pseudomonas aeruginosa (0.5/8), Acinetobacter baumannii (0.25/2), Haemophilus influenzae (0.12/0.25), and Moraxella catarrhalis (0.03/0.06). According to the regression curve, the zone diameter breakpoints were 24 and 19 mm for MICs of 1 and 4 mg/L, respectively. This study confirms the potent in vitro activity of doripenem against Pseudomonas aeruginosa, Acinetobacter, Enterobacteriaceae, MSSA, MSCoNS, and respiratory pathogens. According to the EUCAST MIC breakpoints (mg/L) ≤1/>4 for Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter, and ≤1/>1 for streptococci, pneumococci, and Haemophilus, the zone diameter breakpoints could be (mm) ≥24/<19 and ≥24/<24, respectively.

[How can we optimize medical orderings in intensive care unit (ICU)?]. / Optimisation des prescriptions en réanimation.

OBJECTIVES: To evaluate whether intensivists would accept to optimize their orderings of biological samplings, x-rays and target drugs and to assess the consequence on patient's outcome. STUDY DESIGN: Monocentric evaluation of medical economic procedure. METHODS: Meetings of consultants, registrars and residents started on Dec 21, 2006 with two to three sessions a year in order to evaluate the process of medical ordering. The physicians and pharmacists gave the results of orderings at each meeting. Orderings of systematic samplings, bedside x-rays and unjustified expansive drugs were discouraged, but target samplings and lung ultrasonography were encouraged. New residents were systematically taught about this programme. Meanwhile, monthly morbidity-mortality meetings were pursued in order to assess the consequences of this politics. RESULTS: While ICU total production increased by 3.4% and potentially evitable deaths decreased by 34%, annual expenses decreased by approximatively € 777,000 from 2006 to 2008. This was due to decreased orderings in biology by 30%, bedside x-rays by 10%, computed tomographic scans by 16% and target drugs by 35%. However, an increased ordering in four target drugs was observed in 2008 as compared with 2007. CONCLUSION: Multidisciplinary optimization of medical ordering can be efficient in ICU. However, a profit-sharing with ordering physicians would be necessary to prolong these effects.

Methicillin-resistant Staphylococcus aureus among a network of French private-sector community-based-medical laboratories.

OBJECTIVE: The aim of this study was to estimate the frequency of methicillin-resistant Staphylococcus aureus (MRSA) strains in the French community and the proportion of Panton-Valentine (PVL)-MRSA. DESIGN: A cross-sectional study was made during a 3-month period in 2003 through a network of private-sector, community-based medical laboratories selected throughout France: the Labville network. Each MRSA isolate was included and characterized by French National Reference Center for Staphylococci. The total number of S. aureus isolates was also collected. RESULTS: Among the 283 patients infected or colonized by MRSA, 166 (59%) were considered as healthcare-associated, 14 (5%) as nursing-associated and 39 (14%) as community-acquired. The proportion of methicillin resistance among S. aureus was 14%. Taking into account the sampling design, the incidence of MRSA cases in French outpatients was estimated to be 0.50 [CI95%: 0.41-0.60] per 10,000 inhabitants. The molecular analysis confirmed that 80.6% belong to the Lyon clone, the most prevalent hospital MRSA clone spreading in France and 10.6% to a closely related clone. An emerging MRSA clone containing the tst1 gene was detected in six patients and the PVL-positive ST80 clone only in one, 22-year-old, patient. CONCLUSION: Most of MRSA cases diagnosed in the community in France, in 2003, were elderly with specific risk factors and harbored hospital strains. The prevalence of PVL-MRSA remained low.

Effect of antibiotics, alone and in combination, on Panton-Valentine leukocidin production by a Staphylococcus aureus reference strain.

The capacity of Staphylococcus aureus strain LUG855 to release Panton-Valentine leukocidin (PVL) in the presence of sub-inhibitory concentrations of anti-staphylococcal drugs was examined. Oxacillin enhanced PVL release 2.5-fold, while clindamycin, linezolid, fusidic acid and rifampicin were inhibitory, and vancomycin, pristinamycin, tetracycline, ofloxacin and co-trimoxazole had no effect. In combination with oxacillin, sub-inhibitory concentrations of clindamycin or rifampicin inhibited PVL induction significantly, linezolid was less inhibitory, and fusidic acid did not inhibit PVL induction by oxacillin. These data support the use of oxacillin in combination with clindamycin, rifampicin or linezolid for the treatment of PVL-positive S. aureus infections.

Prevalence of Staphylococcus aureus toxins and nasal carriage in furuncles and impetigo.

BACKGROUND: The precise role of Staphylococcus aureus toxins and nasal carriage in common skin infections remains unclear. OBJECTIVES: To seek correlations between toxin expression, S. aureus nasal carriage and clinical manifestations in patients with community-acquired furuncles and impetigo. METHODS: From November 2004 to August 2005, we studied clinical data and bacteriological samples prospectively collected from 121 patients presenting with furuncles or impetigo. RESULTS: Sixty-four patients (31 with furuncles and 33 with impetigo) had S. aureus-positive skin culture. Panton-Valentine leukocidin (PVL) genes were present in 13 of 31 (42%) isolates from furuncles and were associated with epidemic furunculosis. Exfoliative toxin genes were present in 10 of 10 (100%) and 12 of 21 (57%) bullous and nonbullous impetigo isolates, respectively. Nasal carriage of S. aureus was found in 58% of patients overall. It was strongly associated with chronic furunculosis but not with simple furuncles (88% vs. 29%, P < 0.007). Skin and nose isolates from a given patient always had identical characteristics. Methicillin-resistant S. aureus accounted for four of 64 (6%) positive skin cultures. CONCLUSIONS: PVL is not involved in all types of furuncles but is associated with epidemic furunculosis. Both bullous and nonbullous forms of impetigo are associated with exfoliative toxins. Staphylococcus aureus nasal carriage is associated with the chronicity of furuncles.

[Rhône-Alpes observatory of Streptococcus pneumoniae in 1999: 35 cases of meningitis]. / Observatoire Rhône-Alpes du pneumocoque en 1999: 35 cas de méningites.

In 1999, in Rhône-Alpes region, in a survey of resistance to antibiotics of Streptococcus pneumoniae, 35 cases of meningitis were observed. A retrospectic questionnary was sent to each participant. MICs to Penicillin, Amoxicillin and Cefotaxime were determined with ATB-PNEUMO gallery or E-test and by disk diffusion for the other antibiotics. The results were interpreted according to the recommendations of the CA-SFM. Mean age was 38.1 years (range : 1 month -78 years) and sex-ratio 2/5. Eight patients had previously received antibiotics, 22 patients had risk factors and 23 were transferred in intensive care unit. The patients received C3G + glycopeptide in 15 of 16 children and in 13/19 adults according to the consensus recommendations. Diagnostic was made on the direct examination of CSF in 83%, and blood cultures was positive in 74.3% of cases. The percentage of PRP was 48.6% with 17.1% of intermediate-amoxicilline and 14.3% intermediate-cefotaxime strains. Resistance to trimethoprim-sulfamethoxazole was 45.7%, to chloramphenicol 30% and to fosfomycin 6.9%. All the strains were susceptible to rifampicin and vancomycin. Among the 17 PRP strains, 7 were belonging to serotype 6 (6 in children). The clinical outcome was fatal in 7 male cases (20%), without risk factors in 3 children and 6 of 7 strains were susceptible to penicillin. Six patients (17%) had auditive and/or neurologic sequellaes. This study shows that nearly 50% of strains isolated in meningitis, in Rhône-Alpes region, were not susceptible to penicillin, and confirms the frequency of sequellaes while the mortality is not related with the resistance of strains to the antibiotics.

Multicenter evaluation of an automated system using selected bacteria that harbor challenging and clinically relevant mechanisms of resistance to antibiotics.

A multicenter study was carried out to evaluate the performance of a new commercial automated system in comparison with that of the reference agar dilution method. Ten clinical microbiology laboratories tested a collection of 61 strains of gram-negative bacilli (49 Enterobacteriaceae and 12 Pseudomonas aeruginosa), and 6 other laboratories tested a collection of 55 strains of gram-positive cocci (10 enterococci and 45 staphylococci) against 10-20 antimicrobial agents. The strains were selected on the basis that they harbored challenging and characterized mechanisms of resistance. In comparison with the agar reference method, the automated system gave an overall essential agreement (+/-1 dilution) of 94.5%, 93.5%, and 97% for the gram-negative bacilli, enterococci, and staphylococci, respectively. According to the interpretive standards of the National Committee for Clinical Laboratory Standards, the category agreement ranged from 96 to 96.4% for the three sets of organisms. The accuracy of the automated system, as determined by the kappa test, ranged from 0.80 to 0.88, reflecting an almost perfect agreement with the reference technique. Very major, major, and minor errors obtained with the automated system were 0.3%, 2.9%, and 6.6% for gram-negative bacilli, 3.4%, 0%, and 5% for enterococci, and 1%, 1.6%, and 2.7% for staphylococci, respectively. The high rate of very major errors in enterococci was mostly due to a single strain of multidrug-resistant Enterococcus faecium, which was found susceptible to several antibiotics in a majority of participant laboratories. The use of a heavy inoculum and of a broth test medium by the automated system might account for a better expression of certain resistance mechanisms, including beta-lactamases, as compared to the agar dilution reference method. The interlaboratory reproducibility was acceptable, as shown by the narrow dispersion of MICs and by the results of quality control.

[Evaluation of the E-test and the ATB-PNEUMo battery for determining the beta-lactam MIC for Streptococcus pneumoniae in daily practice]. / Evaluation du E-test et de la galerie ATB-PNEUMo dans la détermination des CMI aux bêtalactamines de Streptococcus pneumoniae en pratique quotidienne.

In 1999, during the survey of resistance of Streptococcus pneumoniae to antibiotics by 31 clinical laboratories of Rhône-Alpes area, MIC to penicillin (P), amoxicillin (AMX) and cefotaxime (CTX) of 877 PRP strains or with a diameter of inhibition to oxacillin inferior to 26 mm, were determined by each institution by E-test (n = 220 strains) or ATB-PNEUMO (n = 657 strains). MICs of these three antibiotics were determined by dilution in agar medium by the coordinating center. The essential agreement was respectively for ATB-PNEUMO and E-test 89% versus 84% for P (p > 0.05), of 86% vs 79% for AMX (p < 0.01), and of 91% vs 86% for CTX (p = 0.03). When the strains were classified in clinical category, the differences were significant (p < 0.001) for AMX (85% vs 71%) and for CTX (82% vs 75%) but not for P (73% vs 78%). ATB-PNEUMO method was more sensitive than E-test for the detection of strains susceptible to P (90 vs 73%), to AMX (83 vs 78%) and to CTX (80 vs 72%) and for the strains intermediate to AMX (90 vs 78%). On the contrary, E-test is more specific than ATB-PNEUMO for the detection of P-resistant strains (94 vs 86%). Finally, the specificity of both methods is the same for detection of P-S, AMX-R and CTX-I strains.

Performance of the chromogenic medium CHROMagar Staph Aureus and the Staphychrom coagulase test in the detection and identification of Staphylococcus aureus in clinical specimens.

CHROMagar Staph aureus (CSAM) (CHROMagar Microbiology, Paris, France) is a new chromogenic medium designed to enable detection of colonies of Staphylococcus aureus by their pink color. A total of 775 specimens were cultured in parallel on CHROMagar Staph aureus and conventional media. Among the 267 S. aureus strains recovered on at least one medium, 263 were isolated on CSAM medium (sensitivity, 98.5%), and 245 (sensitivity, 91.8%) were isolated on conventional media. The specificity of presumptive identification of S. aureus on the basis of pink colony color on CSAM medium was 97% (493 of 508). This specificity increased to 100% when coagulase detection with the Staphychrom coagulase test was added and to 98.8% when S. aureus surface components were detected by agglutination in the Pastorex Staph Plus test. Susceptibility testing of 67 S. aureus strains, performed in parallel on pink CSAM colonies and on colonies grown on blood agar, gave similar results. Thus, rapid and accurate recognition and identification of S. aureus isolates were achieved with CSAM as the primary isolation medium, followed by the staphylocoagulase Staphychrom test. Antimicrobial susceptibility testing (disk-diffusion method or ATB STAPH System) can be performed directly on pink CSAM colonies.

Incidence of Staphylococcus aureus with reduced susceptibility to glycopeptides in two French hospitals.

OBJECTIVES: To determine the incidence of Staphylococcus aureus isolates with reduced susceptibility to glycopeptides among all clinical isolates collected consecutively in two French hospitals between November 1998 and April 1999. METHODS: Methicillin-resistant and -susceptible S. aureus isolates were screened on vancomycin- or teicoplanin-supplemented agar plates. Glycopeptide MICs were determined by the E test procedure with a high inoculum and by an agar dilution technique. Glycopeptide-intermediate S. aureus isolates were identified as homogeneously or heterogeneously resistant to vancomycin by performing population analysis. RESULTS: Of the 640 isolates recovered from 518 patients, three from the same patient and two from two different patients showed homogeneous or heterogeneous intermediate resistance to vancomycin. CONCLUSION: The incidence of glycopeptide-intermediate S. aureus (homogeneously or heterogeneously resistant) in a non-selected patient population, i.e. regardless of predisposing factors and glycopeptide therapeutics, remains low in the two French hospitals involved in the study, representing 0.6% of isolates.

[Epidemic of Staphylococcus aureus nosocomial infections resistant to methicillin in a maternity ward]. / Epidémie d'infections nosocomiales à Staphylococcus aureus résistant à la méticilline dans une maternité.

Methicillin-resistant Staphylococcus aureus (MRSA) nosocomial infections frequently occur in the hospital environment, but their incidence is less often observed in neonates. In the present investigation, seventeen cases were recorded over a nine-week period (two cases per week). Pulsed field gradient gel electrophoresis confirmed the clonal character of the strain. The hypothesis of manually-transmitted infection due to contamination from multiple sources was reinforced by the fact the epidemic persisted in spite of the elimination of the main human infectious source and an absence of risk factors determined by the case-control study. The role of environmental factors in the persistence of this outbreak of MRSA infection has been considered.

Clinical isolate of vancomycin-heterointermediate Staphylococcus aureus susceptible to methicillin and in vitro selection of a vancomycin-resistant derivative.

A Staphylococcus aureus strain with low-level heteroresistance to vancomycin (designated MER) but susceptible to methicillin was isolated from an outpatient with conjunctivitis who did not receive any glycopeptide antibiotics. Incubation of the parent strain, MER, with increasing concentrations of vancomycin led to rapid selection of a stable progeny homogeneously resistant to vancomycin. Electron micrographs of strain MER showed enhanced cell wall thickness and abnormal septations typically seen with methicillin-resistant S. aureus having intermediate susceptibility to vancomycin.

[Indicators of quality for hospital antisepsis]. / Indicateurs de qualité pour l'antisepsie à l'hôpital.

In any health care institution, the most important quality indicator for antisepsis is the existence of systems of reference of use, secondly the knowledge of those systems and then the compliance by the different classes of professionals. These refrentials must be regularly evaluated and updated according to general consensus.

Distribution of genes encoding resistance to macrolides, lincosamides, and streptogramins among staphylococci.

The relative frequency of 10 determinants of resistance to macrolides, lincosamides, and streptogramins was investigated by PCR in a series of 294 macrolide-, lincosamide-, and/or streptogramin-resistant clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci isolated in 1995 from 32 French hospitals. Resistance was mainly due to the presence of ermA or ermC genes, which were detected in 259 strains (88%), in particular those resistant to methicillin (78% of the strains). Macrolide resistance due to msrA was more prevalent in coagulase-negative staphylococci (14.6%) than in S. aureus (2.1%). Genes related to linA/linA' and conferring resistance to lincomycin were detected in one strain of S. aureus and seven strains of coagulase-negative staphylococci. Resistance to pristinamycin and quinupristin-dalfopristin was phenotypically detected in 10 strains of S. aureus and in three strains of coagulase-negative staphylococci; it was always associated with resistance to type A streptogramins encoded by vat or vatB genes and occurred in association with erm genes. The vga gene conferring decreased susceptibility to type A streptogramins was present alone in three strains of coagulase-negative staphylococci and in combination with erm genes in 10 strains of coagulase-negative staphylococci. A combination of vga-vgb-vat and ermA genes was found in a single strain of S. epidermidis.

[Pneumococcus observatory data in the Rhône-Alps region. Results from 1996]. / Observatoire du pneumocoque en région Rhône-Alpes. Résultats de l'année 1996.

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%).

[Comparison of the results of the Etest and the method for determining minimum inhibitory concentrations in solid media for penicillin G, amoxicillin, and cefotaxime for S. pneumoniae. A multicenter study]. / Comparaison des résultats du Etest et de la méthode de détermination des concentrations minimales inhibitrices en milieu solide pour la pénicilline G, l'amoxicilline et le céfotaxime chez S. pneumoniae. Une étude multicentrique.

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.