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OBJECTIVES: To quantitatively compare the antibiotic susceptibility of biofilms formed by the coagulase-negative staphylococci (CoNS) Staphylococcus epidermidis and Staphylococcus haemolyticus with the susceptibility of planktonic cultures. METHODS: Several CoNS strains were grown planktonically or as biofilms to determine the effect of the mode of growth on the level of susceptibility to antibiotics with different mechanisms of action. The utility of a new, rapid colorimetric method that is based on the reduction of a tetrazolium salt (XTT) to measure cell viability was tested by comparison with standard bacterial enumeration techniques. A 6 h kinetic study was performed using dicloxacillin, cefazolin, vancomycin, tetracycline and rifampicin at the peak serum concentration of each antibiotic. RESULTS: In planktonic cells, inhibitors of cell wall synthesis were highly effective over a 3 h period. Biofilms were much less susceptible than planktonic cultures to all antibiotics tested, particularly inhibitors of cell wall synthesis. The susceptibility to inhibitors of protein and RNA synthesis was affected by the biofilm phenotype to a lesser degree. Standard bacterial enumeration techniques and the XTT method produced equivalent results both in biofilms and planktonic assays. CONCLUSIONS: This study provides a more accurate comparison between the antibiotic susceptibilities of planktonic versus biofilm populations, because the cell densities in the two populations were similar and because we measured the concentration required to inhibit bacterial metabolism rather than to eradicate the entire bacterial population. While the biofilm phenotype is highly resistant to antibiotics that target cell wall synthesis, it is fairly susceptible to antibiotics that target RNA and protein synthesis.
Liver fibrosis is currently described quite subjectively or, at best, semiquantitatively by scoring systems. In order to measure the severity of liver fibrosis quantitatively and to compare this with established methods, such as Knodell's scoring system, the colorimetric method and conventional description reports, we undertook the present study. A personal computer with an image grabber card and a microscope equipped with a computer-controlled slide-driver was used for computer morphometry. The principle behind morphometry is based on the different colours of hepatocytes and fibres following staining with Masson's trichrome stain. There were 31 patients (25 male, six female) recruited into the present study with a mean +/- SD age of 41.6 +/- 15 years (range 24-66 years). Of these patients, 16 had chronic hepatitis B, 12 had chronic hepatitis C and three were alcoholics. Colorimetric methods and Knodell's fibrosis score were performed according to established protocols. Conventional description reports were obtained from reviews of patient charts. The results from computer morphometry were highly correlated with results from the colorimetric method, with a correlation coefficiency gamma = 0.85 (P<0.0001). The results from computer morphometry also correlated with both Knodell's scoring system (gamma = 0.69; P<0.001) and conventional description reports (gamma = 0.46; P<0.01). Results from Knodell's scoring system were significantly correlated with computer morphometry, as follows: score 0, 2.7 +/- 1.4; score 1, 5.7 +/- 1.2; score 2, 7.7 +/- 2.3; score 3, 10.7 +/- 3.2; score 4, 21.8 +/- 14.1. The trend was statistically significant by the Wilcoxon rank sum test. In conclusion, our computerized morphometry system is a reliable tool for the evaluation of the severity of liver fibrosis and can be used as a tool for the objective quantification of liver fibrosis.
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Color parameters were measured on 50 psoriatic plaques in 10 patients, after scoring the amount of scales on them by inspection, with a narrow-band reflectance spectrophotometer (erythema/melanin index expression) and tristimulus colorimeter (CIE L*a*b* expression). Both erythema index a* (redness) were highest in the group of erythematous plaque with little scale (twice as high as in controls) and decreased significantly as the plaques were covered with thicker scale, while L* (brightness) changed in just the opposite fashion of a*. These portable 'color indicators' can be utilized to express the appearance of psoriatic plaques quantitatively, especially the extent of erythema and the amount of the scale on it.
Judgments of appearance matching by means of the visual criteria established by the United States Public Health Service (USPHS) and by means of an extended visual rating scale were determined for composite resin veneer restorations and their comparison teeth. Using a colorimeter of 45 degrees/0 degrees geometry and the CIELAB color order system we used the color of the restorations and comparison teeth to calculate a color difference for every visual rating. Statistically significant relationships were found between each of the two visual rating systems and the color differences. The average CIELAB color difference of those ratings judged a match by the USPHS criteria was found to be 3.7. However, the overlap in ranges of the color differences for those comparisons rated matches and mismatches indicates the importance of other factors in appearance matching, such as translucency and the effects of other surrounding visual stimuli. The extended visual rating scale offers no advantages to the more broadly defined criteria established by the USPHS.
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