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.

In vitro activity of teicoplanin against gram-positive cocci.

The glycopeptide susceptibility of 443 clinical isolates of gram-positive cocci collected from nine general hospitals in 1996 was determined according to the recommendations of the CA-SFM (the Antibiogram Committee of the French Society for Microbiology). In total, 234 isolates of Staphylococcus aureus, 84 isolates of coagulase-negative staphylococci (CNS), 98 enterococci and 27 streptococci were collected. The mecA gene confirming resistance to methicillin was found in 42.7% of S. aureus isolates and 51.2% of CNS isolates. No resistance to teicoplanin and vancomycin was found in S. aureus but four isolates of CNS had an MIC of teicoplanin > or = 8 mg/L. All isolates of Enterococcus faecalis tested were susceptible to both glycopeptides. This study confirms that teicoplanin has a very good in vitro activity against gram-positive cocci, isolated in France from nosocomial infections.

Mercury exposure in French Guiana: levels and determinants.

Mercury is used widely for gold extraction in French Guiana and throughout the entire Amazon basin. To evaluate contamination among the general population, the authors chose individuals who attended 13 health centers and maternity hospitals dispersed geographically across the territory and served Guiana's different populations. Five hundred individuals (109 pregnant women, 255 "other" adults, and 136 children) who received care at one of the centers were selected randomly for this study. Each individual answered a questionnaire and provided a hair sample. The authors determined mercury in hair with atomic absorption spectrometry. The following mean levels of mercury were observed: 1.6 microg/g (95% confidence interval [CI]=1.3, 1.9) among pregnant women; 3.4 microg/g (95% CI=3.0, 3.9) among other adults; and 2.5 microg/g (95% CI=2.1, 3.0) among children. Diet factors contributed the most to mercury levels, especially consumption of freshwater fish (mean=6.7 microg/g for individuals who ate fish more than 5 times/wk) and livers from game. Other factors, including age, dental amalgams, use of skin-lightening cosmetics, and residence near a gold-mining community, did not contribute significantly to mercury levels. Overall, 12% of the samples contained mercury levels in excess of 10 microg/g, but in some Amerindian communities up to 79% of the children had hair mercury levels that exceeded 10 microg/g. The results of this study indicated that (a) diet played a predominant role in total mercury burden, and (b) in some communities, mercury contamination exceeded safe levels.

Effects of pregnancy on the inter-individual variations in blood levels of lead, cadmium and mercury.

Blood samples to be analysed for lead, cadmium and mercury were taken from 417 pregnant women not occupationally exposed to these metals. Each subject was paired with a non-pregnant woman of the same age (+/- 2 years), socio-economic status, alcohol and tobacco status. Most of the inter-individual variations observed in earlier studies were confirmed in the control group. Among the pregnant women, however, such variations in blood metal levels appeared to be somewhat different compared to the control women according to the parameters studied: age of the women, alcohol and tobacco consumption. Furthermore, the study of the evolution of blood levels of lead, cadmium and mercury throughout pregnancy revealed a significant decrease in cadmium levels during the first half of pregnancy. A similar tendency was observed for lead but this did not attain statistical significance.

The combined effect of tobacco and alcohol consumption on the level of lead and cadmium in blood.

This study deals with the person-to-person variation in the levels of lead and cadmium in the blood of 6437 subjects (2883 men and 3554 women). The lead level (Pb-B) is clearly higher in men than in women, and the cadmium level (Cd-B) is a little higher in men than in women. Only the Pb-B varies according to age for both sexes. The results reveal that the consumption of alcohol could play an important part in the variation of lead and cadmium levels in the blood; the consumption of alcohol is associated with an increase in Pb-B but a decrease in Cd-B. These variations involving alcohol consumption remain significant regardless of smoking habits. On the other hand, an increase in Pb-B and Cd-B has been noted among smokers and, to a lesser degree, among former smokers, compared with non-smokers.

A collaborative evaluation of a rapid automated bacterial identification system: the Autobac IDX.

A collaborative evaluation of the Autobac IDX, a rapid, semi-automated bacterial identification system, was performed in three independent laboratories in three European countries. The system utilises growth inhibition by a series of chemical compounds. Subsequent analysis of the resultant data by quadratic discriminant function automatically results in a bacterial identification. Three sets of 30 strains were examined repeatedly in each of the participating laboratories. The reproducibilities obtained ranged from 85.6% to 96.6%, with an overall average of 91.8%. The accuracy of the system was also determined by examining 1076 isolates from the three participating laboratories. An overall accuracy of 90.3% was calculated by comparing the Autobac result with a reference method. When the results were weighted to represent clinical frequency, the accuracy was 93.6%.