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; β-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), β-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.

[Rhône-Alpes observatory of Streptococcus pneumoniae in 1999: 35 cases of meningitis]

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]

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]

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]

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.

[Pneumococcus observatory data in the Rhône-Alps region. Results from 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%).

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.

[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]

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.

Kinetics of chlorhexidine on intact skin following a single application

Residual chlorhexidine concentrations were measured after application of a single dose on the skin of 22 healthy volunteers. Dosage by high-pressure liquid chromatography in the skin cleansers revealed that the residual concentrations were higher than chlorhexidine MICs for most organisms of the resident skin flora and some responsible for hand-borne infections, even 24 h after application.

[Actinomyces meyeri disseminated actinomycosis disclosing pulmonary carcinoma]

The diagnosis of severe actinomycosis parallel to that of neoplasia leads to speculation of a possible fortuitous association. Because underlying conditions such as immuno-suppression are suspected in such disease, and to strengthen this hypothesis, we report one more case of disseminated actinomycosis associated with a malignant disease, namely an epidermoid pulmonary carcinoma. The diagnosis was made by thoracotomy a few months after the infectious episode. Two years later the patient recovered. The analysis of the literature data is in favor of a fortuitous association between both diagnoses.

[Bactericidal activity determination of Biseptine, combination of chlorhexidine, benzalkonium chloride and benzylic alcohol, on 124 hospital bacterial strains]

Biseptine is an antiseptic composed of chlorhexidine digluconate (CHX), benzalkonium chloride (BC) and benzylic alcohol. Minimal Bactericidal Concentrations (MBCs) of Biseptine were determined on 124 clinical strains: 76 Enterobacteriaceae, 16 other Gram negative bacilli, (Pseudomonas spp, Aeromonas spp, Haemophilus spp) and 32 Gram positive bacteria (Staphylococcus spp, Streptococcus spp, Listeria spp, Bacillus cereus), using microdilution method, in comparison with Hibitane Champ. Modal MBC of Biseptine was 25 mg/l of CHX/2.5 mg/l BC (1/100 dilution). Proteus (MBC: 133 mg/l CHX/ 13 mg/l CB) and B. cepacia (MBC: 100 mg/l CHX/ 10 mg/l CB) were the most resistant strains, as expected with cationic antiseptics. 4/5 Bacillus cereus, strains were weakly susceptible to Biseptine and Hibitane Champ. In Biseptine, the association of CHX and CB showed a synergic activity, MBCs are usually 2 fold lower that Hibitane Champ MBCs.

[Kinetics of in vitro bactericidal activity of the antiseptic biseptine combining 3 active principles]

Biseptine, is an association of chlorhexidine digluconate, benzalkonium chloride and benzylic alcohol. Little is known, in literature, on this antiseptic, used for cutaneous antisepsis. We studied killing kinetic of Biseptine, at different concentrations, on 4 AFNOR bacterial strains. Killing curves were studied at antiseptic concentration of 90 to 0.1% in 10 ml of distilled water. Bacterial counts were determined after neutralization in liquid medium. Synergy of chlorhexidine and benzalkonium chloride in Biseptine, allowed to obtain similar bactericidal activity than Hibitane champ with chlorhexidine concentrations 2 fold less. At 90, 50, 25, 10 and 5% concentrations, bactericidal activity (5 log10 reduction of the initial bacterial count) was effective in one minute. After 5 to 15 minutes, activity persisted at 1 and 0.5% concentrations. The 0.1% solution was inefficacious. This report disclosed an important security margin in antiseptic activity.

Phenotypic and genotypic (pulsed-field gel electrophoresis) characteristics of enterotoxin-A-producing Staphylococcus aureus strains

The phenotypic (antibiotype, serotype, phagetype) and genotypic (SmaI restriction patterns using pulsed-field gel electrophoresis) characters of 162 Staphylococcus aureus epidemiologically unrelated strains were studied. Eighty-two of the isolates produced enterotoxin-A (SEA+), while 80 produced none (SEA-). None of the phenotypic characters observed were characteristic of SEA+ strains. On the other hand, the electrophoretic profiles revealed a non-random distribution of the SEA+ strains (p < 0.01 in groups PI and PIII, and p < 0.03 in group PII). It can therefore reasonably be assumed that the enterotoxin-A-producing strains did not constitute a single clone, but rather, seemed to belong to strains derived from at least three clones with distinct genetic organization.

[In vitro antibacterial activity of a new fluoroquinolone, sparfloxacin, against nosocomial bacteria, and concordance curve]

Minimal inhibitory concentrations (MICs) of sparfloxacin (SFX) were determined by agar dilution for 3,164 bacterial strains isolated in 10 university hospitals; in addition, antibiograms by agar diffusion were performed with 5 micrograms disks. Activity of SFX against nalidixic acid (NAL) susceptible (S) Enterobacteriaceae was close to that of other fluoroquinolones (FQ) (MIC 50 and 90: 0.06-0.5 microgram/ml); like for other FQ, this activity was reduced against NAL intermediate and resistant (R) Enterobacteriaceae (2-16). MICs of SFX against P. aeruginosa were between 0.12 and 16 (1-32). SFX had also a good activity against NAL-S A. baumannii (CMI < or = 0.25) but this activity is reduced against NAL-R Acinetobacter (16). SFX was highly active against Haemophilus (0.016-0.06) gonococci (0.008), meningococci (0.008) and B. catarrhalis (0.008-0.03). SFX showed activity superior to the currently available FQ against methicillin susceptible staphylococci (0.06); the resistant strains [8] are usually methicillin resistant. SFX is more effective against enterococci (0.5), streptococci (0.25-0.5) and particularly pneumococci (0.25-0.5) including penicillin-resistant strains. The coefficient correlation of the regression curve is 0.876; for MIC breakpoints of 1 and 2 micrograms/ml, zone diameter breakpoints should be 20 and 16 mm.

[Comparison of different phenotypic methods with polymerase chain reaction (PCR) for the detection of resistance to oxacillin in coagulase negative staphylococci]

The mecA gene which confers the oxacillin resistance has been searched by PCR in 290 (124 positives, 166 negatives) coagulase-negative staphylococci (CNS) belonging to twelve species. The results were compared with the oxacillin MIC values obtained by agar dilution (4% NaCl) or by the ATB STAPH method (Api-bioMérieux; 0%, 2%, 5% NaCl) and growth inhibitory diameters obtained by agar diffusion with an oxacillin disk placed at 30 degrees C without NaCl, or at 35 degrees C in presence of 2% or 5% NaCl. Sensitivity of oxacillin resistance detection depends upon the salt concentration and the method used. The optimum concentration is 2%. With this concentration, the Api ATB test appears as the more performant (sensitivity: 89.8%). Search for the mecA gene by PCR represents a very interesting method that detects 96.9% of the oxacillin-resistant CNS strains.

[Relationship between the level of minimal inhibitory concentrations of five antiseptics and the presence of qacA gene in Staphylococcus aureus]

The Polymerase Chain Reaction (PCR) was used to detect the qacA gene which encodes antiseptic resistance in 186 clinical isolates of Staphylococcus aureus. The results were compared with those obtained by MIC determination of 4 antiseptics (benzalkonium chloride, hexamidine, chlorhexidine, acriflavine) and for ethidium bromide. The qacA gene was not detected among the 32 susceptible S. aureus strains, but was found in the 70 (85%) of the 82 S. aureus strains resistant to all 5 antiseptics. The gene was also detected in 70 (45%) of the 154 remaining strains that were resistant to at least one antiseptic.

Laboratory diagnosis of oxacillin resistance in Staphylococcus aureus by a multiplex-polymerase chain reaction assay

A polymerase chain reaction (PCR) test was developed in which the mecA gene responsible for the intrinsic resistance to oxacillin in Staphylococcus aureus and the gyrA gene, always present in this species, were amplified in one operation. Among the 468 clinical isolates tested, the results obtained for 454 of the isolates (97%) were consistent with those of MIC determination. Discrepant results were noted for strains with low-level oxacillin resistance (MICs, 4-8 micrograms/ml) and mecA gene negative. For these strains, susceptibility to oxacillin was restored in the presence of a beta-lactamase inhibitor, which suggested a resistance by penicillinase hyperproduction. In contrast, all of the high-level resistant strains (MICs, > 8 micrograms/ml) carried the mecA gene. The presence of this gene has frequently been associated with resistance to gentamicin, tetracycline, erythromycin, lincomycin, and pefloxacin. The PCR assay described in this study can be accomplished with ease and total confidence in the clinical microbiologic laboratory for a rapid and effective establishment of antistaphylococcal chemotherapy.

[Evolution of resistance to antibiotics and antiseptics of hospital Staphylococcus aureus strains isolated from 1980 to 1991]

From 1980 to 1991, 925 non epidemic hospital isolates of S. aureus were selected and phage typed. MIC of 20 antibiotics and 4 antiseptics were determined by agar dilution method. The proportion of isolates susceptible to all antibiotics remains constant; however the trend to the resistance is strong during the study period (oxacillin 10-->20%, erythromycin 17-->28%, pefloxacin 4-->19%...). Strains resistant to oxacillin become more and more multiple resistant; some of recent isolates are resistant to 7 antibiotic families. There are very few products active against these strains i.e, glycopeptides (100%), pristinamycin (96%), fusidic acid (94%). This finding implies the need for continuous surveillance at the local and national level.

Endocarditis due to Staphylococcus lugdunensis: report of 11 cases and review

Staphylococcus lugdunensis is a recently described coagulase-negative staphylococcus that has been associated with human infections, including nine reported cases of infective endocarditis. The present study describes 11 other cases of infective endocarditis caused by this organism. The infection occurred in patients whose mean age was 61 years and was community-acquired in most cases. A preexisting cardiac abnormality was present in eight patients. Three of the 11 infections involved prosthetic valves. Ten strains were susceptible to penicillin. The destructive course of the infection, the need for valve replacement, and the high mortality suggest that S. lugdunensis causes a virulent form of endocarditis.

[Evaluation of a micromethod for the bactericidal activity of five disinfectants on 108 hospital strains]

The authors studied 5 disinfectants containing aldehyde and quaternary ammonium against 108 hospital strains. The minimal bactericidal activities (MBC) were determined with a microdilution method and the dilution-neutralization method (AFNOR T 72-150). The microdilution method results were validated using the MBCs of four reference strains tested with the dilution-neutralization method (AFNOR T 72-150). 3 disinfectants proved to be valuable. 1 disinfectant was valuable but with a MBC toward all bacteria only a dilution away from the dilution of use. 1 disinfectant was determined as unsatisfactory as 9.5 p. cent of all strains proved resistant toward it. All disinfectants matched AFNOR standards; but those specifications did not match toward hospital strains. Such an evaluation using a simple and reliable method should be of use.

[In vitro antibacterial activity of a new oral cephalosporin, ceftibuten. Results of a multicenter study]

Minimal inhibitory concentration (MIC) of ceftibuten (CBT) were evaluated by agar dilution for 1,416 bacterial strains isolated in 5 hospitals. For Enterobacteriaceae, MIC 50 and 90% were respectively (micrograms/ml): (I) Naturally non beta-lactamase producing species: E. coli 0.12-0.5, Shigella 0.06-0.12 and Salmonella 0.03-0.12, P. mirabilis 0.16-0.03. (II) Chromosomal penicillinase producing species: K. pneumoniae 0.03-0.5 and K. oxytoca 0.03-0.06. (III) Chromosomal cephalosporin producing species: E. cloacae and C. freundii 1- greater than 128: S. marcescens 0.25-2; indole + Proteus 0.06-0.12. Activity of CBT was not modified on plasmid mediated penicillinase producing strains; however, CBT was inactive on cephalosporinase hyperproducing strains, and its activity was variably reduced on broad spectrum beta-lactamases producing strains. CBT was inactive on P. aeruginosa (MIC greater than or equal to 32) and on A. baumannii (8- greater than 128). Haemophilus and Gonococci, regardless on beta-lactamase production status, were very susceptible to CBT (MIC 50 and 90%: 0.06-0.5 and 0.016-0.06); it is the same situation for Meningococci; B. catarrhalis was generally inhibited by 0.03 to 2 (strains susceptible to penicillin G) and 0.12 to 16 (strains resistant to penicillin G). CBT was inactive on Staphylococci. Enterococci and Streptococci B were generally resistant; Streptococci A, C, G were inhibited by low concentrations: 0.06 to 1 (MIC 50 and 90%: 0.25-0.5), whereas MIC for other Streptococci 0.12 to 128 (MIC 50 and 90%: 8-128) and for Pneumococci were 0.25 to 16 (4-8). These antibacterial properties particularly against Enterobacteriaceae placed CBT in excellent position among oral cephalosporins.

Intestinal decontamination in a polyvalent ICU. A double-blind study

A double blind, placebo-controlled trial was performed to test the efficacy of prevention of nosocomial infections by selective digestive decontamination. Placebo or tobramycin (80 mg) and colistin (100 mg) was given four times daily via the gastric tube. Amphotericin B (500 mg/6 h) was administered to all patients. As our ICU is divided into two separate subunits, intestinal decontamination or placebo was administered alternatively to patients of the two subunits during two 3-month periods, separated by a 2-month period without prevention. The decontamination (n = 97) and placebo groups (n = 84) were similar with respect to age, sex, severity score and diagnostic categories on admission. Intestinal decontamination alone failed to significantly reduce the number of infected patients (26% vs 34.5%, p = 0.20), but was effective on ICU-acquired infections (0.33 vs 0.60, p = 0.02) especially gram-negative infection rates (0.17 vs 0.43, p = 0.01). The onset of the first ICU-acquired infection was delayed (9 vs 13 days, p less than 0.001) and incidence of pneumonia (2 vs 13 cases, p less than 0.01) including bacterial pneumonia (0 vs 8 cases, p less than 0.01) was significantly decreased. However, mean ICU stay and mortality were not significantly modified by intestinal decontamination.

Cefazolin and netilmicin serum levels during and after cardiac surgery with cardiopulmonary bypass

The kinetics of cefazolin and netilmicin were studied in 10 patients undergoing elective cardiac surgery with hemodilution and cardiopulmonary bypass (CPB). During surgery, but before CPB, cefazolin, 25 mg/kg, and netilmicin, 2 mg/kg, were administered intravenously over 30 minutes. For the 48-hour period following CPB, cefazolin, 25 mg/kg, and netilmicin, 1 mg/kg, were administered intravenously every 8 hours. Initiation of CPB was accompanied by a 28% to 30% decrease in hematocrit and serum antibiotic levels. At the conclusion of surgery, cefazolin and netilmicin serum levels were 41 +/- 12 micrograms/L and 2.5 +/- 0.6 micrograms/mL (mean +/- SD), respectively. During the postoperative period, cefazolin levels were consistently greater than the minimum inhibitory concentration (MIC) for sensitive bacteria (4 micrograms/mL); average netilmicin levels were greater than MIC of sensitive bacteria (2 micrograms/mL) for 2 hours after antibiotic infusion. The netilmicin trough levels were 0.6 +/- 0.5 micrograms/mL. Pharmacokinetic parameters were determined using a model-independent method, and gave the following results during surgery: cefazolin--elimination half-life, 231 minutes, total body clearance, 1.05 mL/kg/min, and steady-state volume of distribution, 243 mL/kg. The values for netilmicin were 249 minutes, 1.18 mL/kg/min, and 353 mL/kg, respectively. Postoperatively there were no significant changes in the disposition of cefazolin, but the elimination half-life of netilmicin was shorter (124 minutes, P less than 0.01) and the total body clearance greater (3.58 mL/kg/min, P less than 0.01) than during surgery.

Standardized method for evaluation of hand disinfection by surgical scrub formulations

A standardized protocol for the evaluation of hand disinfection by surgical scrub formulations was applied to volunteers in a multicenter trial. Povidone iodine (PVI), chlorhexidine (CHX), and a nonmedicated soap (NMS) were tested. The scrubbing procedure involved three daily hand washings for five consecutive days; surviving bacteria were counted daily after being collected in a suitable neutralizing solution. Immediate efficacy (IE), cumulative efficacy (CE), and remanent effect (RE) were calculated by reference to the control hand. Statistical analyses of IE, CE, and RE showed significant differences among the three scrub formulations. IEs of PVI and CHX were equivalent and different from IE of NMS; CE and RE of CHX were higher than those of PVI and NMS. On the basis of the statistical analysis, the population size required for further studies aimed at detecting significant differences between surgical scrub formulations could be estimated.

[Determination of bactericidal minimum concentrations of 3 antiseptics and 1 disinfectant on 580 hospital gram-negative bacilli]

Minimal bactericidal activities (MBCs) of three antiseptics (povidone iodine, chlorhexidine digluconate, benzalkonium chloride) and one disinfectant (sodium hypochloride) where determined, on 580 hospital Gram negative bacilli. Previously the Afnor T 72-150 standard for antiseptic and disinfectant was established for two reference strains E. coli CIP 54 127 and P. aeruginosa CIP A 22. No difference was found between the MBC obtained with these strains in Afnor standard and in microdilution method. Microdilution method allows to test 11 hospital isolates and one reference strain. A strain was considered as resistant when the MBC was one dilution higher than the reference strain MBC. Results were as follows: None strain was resistant to sodium hypochloride and povidone iodine; 18.2% Enterobacteriaceae were resistant to chlorhexidine digluconate with 94.2% of Proteus; 4% of Enterobacteriaceae were resistant to benzalkonium chloride with 89.5% of Proteus and only 1.8% other bacilli. Results obtained in the present study are similar as those previously published particularly with Proteus; nevertheless other studies have reported P. aeruginosa strains resistant to chlorhexidine digluconate and benzalkonium chloride; this last point was not observed in our study.

Oxacillin and tobramycin serum levels during cardiopulmonary bypass

Antibiotic prophylaxis in cardiac surgery is recommended to combat acquired infections caused by staphylococci and gram-negative bacilli. Prophylaxis seems effective provided blood levels are greater than minimal inhibitory concentrations (MIC). In this study, two doses of antibiotics were compared in 45 patients with normal renal function during cardiopulmonary bypass (CPB). All patients received 50 mg/kg of oxacillin. Group 1 (30 patients) also received 1 mg/kg of tobramycin, while group 2 (15 patients) received 2 mg/kg of tobramycin. Blood samples were taken after the administration of antibiotics, as well as at the onset and conclusion of CPB. Additional samples were taken before and after heparin injection before CPB, and from the arterial and venous cannulae of the bubble oxygenator during CPB. In both groups, oxacillin serum levels were constantly greater than MIC for susceptible bacteria. In group 1, tobramycin levels less than 2 micrograms/mL (MIC for most susceptible bacteria) occurred in four patients before CPB, in 14 patients at the onset of CPB, and in 19 patients at the conclusion of CPB. These low levels were not explained by heparin administration or absorption onto the CPB circuit, but were the result of hemodilution. In group 2, in which all the tobramycin levels were higher than 2 micrograms/mL, serum levels decreased from 9.9 +/- 3.4 (mean +/- SD) to 3.7 +/- 0.7 micrograms/mL throughout the procedure. Plasma creatinine did not change significantly in either group. It is concluded that in patients with normal renal function, doses as high as 50 mg/kg of oxacillin and 2 mg/kg of tobramycin may be necessary before CPB to provide adequate serum levels throughout CPB.

Clinical isolates of Staphylococcus lugdunensis and S. schleiferi: bacteriological characteristics and susceptibility to antimicrobial agents

The bacteriological characteristics and susceptibility to antimicrobial agents of 108 clinical isolates of Staphylococcus lugdunensis and Staphylococcus schleiferi are described. Fifty out of 108 isolates were considered to be responsible for 16 documented infections, including some severe infections (endocarditis, bacteraemia, osteitis). A number of bacteriological characteristics enabled the identification of these species in the clinical microbiology laboratory: the absence of coagulase and protein A, and the presence of a fibrinogen affinity factor and thermonuclease along with other biochemical characteristics (ornithine and arginine decarboxylases, carbohydrate acidification, novobiocin susceptibility) differentiated these new species from other staphylococci; however, they did not possess virulence markers such as toxins or haemagglutinin, but were haemolytic. In this series, almost all isolates were susceptible to 22 antibiotics and 4 antiseptics representative of the main groups of antimicrobial agents. More information is needed on the ecology and epidemiology of these new opportunistic pathogens.

[Erythromycin and latamoxef in the initial treatment of diffuse peritonitis with visceral failure]

In a thirty months prospective study, 61 patients treated in an Intensive Care Unit received erythromycin (E) (3 g/24 h) and latamoxef (L) (2 g/24 h) as soon as acute peritonitis was surgically confirmed. Five days later, E + L were stopped and nitro-imidazol (NI) was prescribed while searching for a possible infection. The severity of the illness was assessed by clinical study of organ failures and by use of the Simplified Acute Physiology Score (SAPS). 21 patients died (34%): among them 8 of the 19 with postoperative peritonitis. Average SAPS was 17.8 (+/- 4.1) while it was 13 in 631 ICU treated patients (mortality: 22%). Every patient needed mechanical ventilation; pré or per-operative shock has been noted in 41 (67%) and 27 had developed acute renal failure (44%). During E + L, 6 patients died because of an irreversible shock and twice the treatment was not efficient on the isolated bacteria (Pseudomonas aeruginosa, Staphylococcus). No more shock developed post-operatively. During NI, 11 secondary infections (20%) were diagnosed (bacteremia = 6, urinary tractus infection = 4, reactivated arthritis = 1). The bacteria were Streptococcus (n = 6) with Enterococcus (n = 5), Staphylococcus (n = 3) and Pseudomonas aeruginosa (n = 2): they were still respectively sensitive to ampicillin, methicillin and ticarcillin. The association E + L was clinically and biologically well tolerated.

[Proposal for a method of studying the activity of soap or antiseptic against the microbial flora of the hands after a single surgical scrub]

The authors, all members of the Antiseptics group of the Societé Française de Microbiologie, propose a standardised method for the evaluation of the activity of antiseptics on the microbial flora of the hands in the context of surgical scrubbing. This paper defines the aims of the method, its field of application and describes the media and materials required. The various phases of the preliminary study and the definitive trial also described.

[Application of a micromethod to the study of the bactericidal activity of 2 antiseptics based on chlorhexidine gluconate]

Minimal bactericidal concentrations (MBCs) of two antiseptics containing chlorhexidine digluconate (5% for the A solution, 1.5% for the B solution) were determined using a microdilution method. This method is a miniaturization of the Afnor T 72150 standard for antiseptics and disinfectants. 133 hospital isolates were studied, including 68 Enterobacteriaceae, 11 Acinetobacter, 18 Pseudomonas, 1 Achromobacter, 23 Staphylococcus, and 12 S. faecalis. Each microplate was seeded with eleven of these strains and one reference strain (E. coli CIP 54127, P. aeruginosa CIP A22, S. aureus CIP 53154, and S. faecium CIP 5855). Ten microliter of a standardized inoculum (2 to 3 10(8) bacteria/ml) were added to 90 microliters of a solution containing the antiseptic. Each antiseptic was tested in various concentrations (1.95 to 125 mg/l for A and 1.17 to 75 mg/l for B). After five minutes contact at 21 degrees C, 1.5 microliter from each well was seeded on a neutralizing agar plate (letheen agar + 3% tween 80 + 0.3% lecithin + 3% saponin + 0.1% histidine). The neutralizing effectiveness of this plate on the antiseptics in the concentrations used had been ascertained previously. The Afnor T 72150 standard was established for each reference strain. MBCs 90 (in mg/l) found were as follows: 31.2 (A) and 18.8 (B) for Enterobacteriaceae, 15.6 (A) and 9.4 (B) for Acinetobacter, 31.2 (A) and 18.8 (B) for Pseudomonas, 62.5 (A) and 37.7 (B) for Staphylococcus and 125 (A) and 37.5 (B) for S. faecalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the API 20 STREP system for species identification of streptococci associated with infective endocarditis

A rapid commercial system (API 20 STREP gallery, API System, France) for the identification of streptococci was compared with conventional biochemical or serological methods. 77 clinical isolates from patients with infective endocarditis and six reference strains were tested. Biochemical tests showing differences between conventional methods and the API gallery were the acidification of inulin and the Voges-Proskauer reaction, but these differences did not affect the final identification of any strain. 75 strains were identified by the API system and 70 by conventional methods. 69 strains (25 groupable and 44 of 51 non-groupable streptococci) were given the same identity by both methods. One S. morbillorum was only identified by the conventional method. Seven S. sanguis I strains were identified only by the API system and confirmed by additional biochemical tests. The API gallery is a useful method for identifying streptococci associated with infective endocarditis, agreeing with conventional methods in 90% of strains. Results are usually available in 24 h.

[Multicenter study of the antimicrobial activity of antiseptics on the hands. Protocols and results]

Quantitative evaluation of in vivo activity of antiseptics in surgical-type handwashing is achieved by comparing bacterial counts on one hand after disinfection and on the other untreated hand. Handwashing, bacterial recovery and bacterial counts must be performed according to strictly standardized methods. A large number of participants is required.

[Effectiveness of 9 soaps and/or antiseptics on hand flora after surgical-type washing]

We studied the effect of nine soaps and/or antiseptics on the bacterial flora of hands 5 minutes after a surgical scrub. Each agent was used by ten healthy volunteers, free of skin lesions. The following agents were used: chlorhexidine gluconate 4% and 1.5%, povidone iodine 4%, ethanol 70 degrees, isopropanol 70 degrees, a non-antiseptic soap, and another soap followed by either ethanol 70 degrees, isopropanol 70 degrees or a preparation containing H2O2. The surgical scrub procedure varied slightly according to whether or not the agent was soapy and required rinsing. Sampling was carried out using Gaschen's bag method with 400 ml of neutralising solution. Counts were made after 48 hours aerobic incubation at 35 degrees C on tryptic soy agar with 1% Tween 80, and after 8 days anaerobic incubation at 35 degrees C on Brewer's yeast agar with 1% Tween 80. Results were expressed as the log 10 to the number of bacteria per hand. Statistical significance was determined using the Student t test. The greatest reduction in aerobic flora was produced by isopropanol 70 degrees C (1.7 log 10). 1.5 to 0.5 log 10 reductions were produced, in the following decreasing order, by ethanol 70 degrees, povidone iodine, chlorhexidine gluconate 4% and 1.5% and a soap with ethanol 70 degrees. A reduction of less than 0.5 log 10 was produced by a soap with isopropanol 70 degrees, and soaps with H2O2. Similar results were obtained with the facultative anaerobes.

[Verification of the effectiveness of neutralization in the in vivo study of antiseptics]

Well defined controls of the effectiveness of antiseptic neutralizing agents in vitro already exist (Afnor Standards for antiseptics and disinfectants). Conversely, there is currently no standard method for verifying how effectively such agents neutralize antiseptics which have been applied to the skin. We describe a method in which the neutralizing solution is first applied to the antiseptic-treated skin and then filtered to remove skin flora. The effect of the neutralizing agent is then checked using a test organism (Staphylococcus epidermidis ATCC 14990) in parallel with four controls: viability of the test organism (T1), activity of the untreated antiseptic (T2), non-bactericidal effect of the neutralizing agent (T3) and of skin secretions (4). Skin sampling was carried out using Gaschen's bag method for the hands and the Williamson and Kligman method modified by Fleurette for other sites. Twelve soaps and/or antiseptics were studied. In each case, activity of the antiseptic (T2) was confirmed, except when the product under study was a non-bactericidal soap. Bacterial counts obtained in controls T3 and T4 and in the neutralization test itself were always greater than 80% of the control value (T1). Occasionally, the counts in the neutralization test exceeded 100% of the T1 value, probably because of the dispersal effect of the triton X100 present in the neutralizing solution. This method thus offers a means of standardizing the study of antiseptics in vivo. In addition, the test organism, Staphylococcus epidermidis, is more representative of the skin flora than the bacterial strains recommended by Afnor for in vitro studies.