Y. Richard

Comparison of French natural scrapie isolates with bovine spongiform encephalopathy and experimental scrapie infected sheep

We compared the glycoform pattern of the abnormal prion protein (PrP(Sc)) detected by immunoblotting in 21 sheep with natural scrapie, from 21 different outbreaks identified in France since 1996, with a bovine spongiform encephalopathy (BSE)-infected sheep. All the natural scrapie isolates had a higher molecular mass of the unglycosylated PrP(Sc) than in BSE-infected sheep. In the latter case, this molecular mass appeared identical to that found in the CH 1641 experimental scrapie strain (type C pattern), whereas in natural scrapie cases it was similar to that found in the SSBP/1 experimental scrapie strains. These results suggest that all French natural scrapie isolates studied so far would belong, as SSBP/1, to the group of scrapie cases with type A electrophoretic pattern.

Comparison of three immunological methods for detecting staphylococcal enterotoxins from food

Aims:  Immunologically based assays for the detection of staphylococcal enterotoxins are numerous. These techniques include radio immunosorbent assays and enzyme‐linked immunosorbent assays (ELISA), some of which are available as commercial kits. The purpose of this study was to compare the performances of three commercial immunoassays.

Prevalence of Escherichia coli O157:H7 in industrial minced beef

Aims:  The lack of baseline data on the prevalence of Escherichia coli O157:H7 in retail minced beef in France prompted this survey of industrial minced beef production.

Prevalence of verotoxin-producing Escherichia coli (VTEC) in slurry, farmyard manure and sewage sludge in France

Aims: The aims of the present study were to determine VTEC prevalence in manure, slurryand sewage sludge in France and to characterize the VTEC strains isolated (virulence genes and serotype). 
Methods and Results: Seven hundred and fifty‐two samples from 55 farmyard manures, 136 bovine and porcine faeces, 114 slurries, 10 composts, and 437 samples from outflows of sewagewastewater treatment plants were analysed. Twenty‐four percent contained isolates which were PCR positive for stx gene. Twenty‐one VTEC strains were recovered from positive samples by colony hybridization: 76% of them were positive for stx2 gene, 33% for stx1 gene,and 19% for eae gene. One strain belonged to serotype O157:H7 and two others to serogroups O26 and O55, respectively. 
Conclusions: Some of the VTEC strains isolated from environments in France should be considered as potentially pathogenic for humans. 
Significance and Impact of the Study: Appropriate handling or use of manure, slurry andsewage sludge is necessary so that contamination of the environment and food by VTEC can be prevented.

Detection of Escherichia coli O157 in French food samples using an immunomagnetic separation method and the VIDASTME. coli O157

C. VERNOZY‐ROZAND, C. MAZUY, S. RAY‐GUENIOT, S. BOUTRAND‐LOEï, A. MEYRAND AND y. richard. 1997. Two commercially available screening methods, an automated enzyme‐linked fluorescent immunoassay (VIDASTME. coli O157) and an immunomagnetic separation followed by culture onto cefixime tellurite sorbitol MacConkey agar (CT‐SMAC), were compared for detection of Escherichia coli O157 in naturally and artificially contaminated food samples. A total of 250 naturally contaminated food samples, including raw milk cheeses, poultry, raw sausages and ground beef retail samples, were examined. Four poultry, one raw sausage and one ground beef sample were found to be positive for E. coli O157 by both methods. Of the six positive samples, five were shown to contain sorbitol‐positive, O157‐positive, H7‐negative, motile and non‐verotoxin‐producing E. coli.

Exoprotein and slime production by coagulase-negative staphylococci isolated from goats' milk.

Milk from mastitis-free goats from French herds was examined for the presence of coagulase-negative staphylococci (CNS), and 165 positive isolates were evaluated for their capacity to produce exoproteins. Most isolates were identified as Staphylococcus caprae (N = 91) or S. xylosus (N = 36), but members of at least nine other species were present. Overall, some 57% of isolates produced toxins with phenotypic properties of alpha-hemolysin, and 75% produced toxins resembling S. aureus beta and/or delta-hemolysins. Thermostable desoxyribonuclease (TNAse) was secreted by 29% of isolates and thermolabile DNAse by 66%. Slime was produced by 42% of our cultures and, although none of them showed activity to insoluble elastase, over 70% lysed the soluble substrate. No clinical consequences were observed to correlate with exoprotein production, which proved to be inconstant within individual CNS species.

Kinetics and metabolic specificities of Vero cells in bioreactor cultures with serum-free medium.

The aim of this study was to understand the metabolism kinetics of Vero cells grown on microcarriers in bioreactors in serum-free medium (SFM). We sought to determine what nutrients are essential for Vero cells and how they are consumed. Contrary to glucose and to most of the amino acids, glutamine and serine were very quickly depleted in this medium and can be supposed to be responsible for cell apoptosis. Lactate and ammonium ions did not reach toxic levels for Vero cells. We payed more attention to the lactate metabolism. Usually we observed that after about 2 days lactate was consumed in serum-containing media, but its concentration plateaud in SFM. Moreover, the addition of serum in SFM provoked lactate consumption and the rate of glucose and glutamine consumption was twice as high as in the SFM not supplemented with serum. The depletion of glutamine and serine and the metabolic deviations leading to a shortage of intermediate products required for other metabolic pathways probably contribute to the lower cell yield and higher cell death rate in SFM.

Antimicrobial susceptibility testing of actinomyces pyogenes: Comparison of disk diffusion test and Api ATB Strep system with the Agar dilution method

The use of the disk diffusion and the Api ATB Strep system or a related technique for a few antibiotics was compared with the agar dilution method for antimicrobial susceptibility testing of 103 clinical isolates of Actinomyces pyogenes. There was complete agreement between disk diffusion and MIC in 98.8%, with minor errors, in 0.7% and with very large errors, in 0.5% of cases. The common criteria for the interpretation of zones could be kept for penicillin G, amoxicillin, methicillin, cephalothin, erythromycin, lincomycin, pristinamycin, vancomycin, rifampin, streptomycin, kanamycin, gentamicin and chloramphenicol. The proposed breakpoints for a tetracycline 30 IU disk were > or = 22 mm for susceptibility and < 22 mm for resistance. There was complete agreement between the ATB strip system and MIC in 98.3% of cases, with minor errors in 0.9% and with very large errors, in 0.8% of cases. All the dissimilarities were due to streptomycin and tetracycline and results could not be reported for these 2 antibiotics when using this system. Wells with kanamycin and gentamicin at low concentrations as well as chloramphenicol should be included by the manufacturer.