The influence of various concentrations (0.003-8 mg/mL) of N-acetylcysteine on the formation of biofilms by 15 strains of Staphylococcus epidermidis has been studied. A dose-related decrease in biofilm formation was observed, except with the lowest concentrations. The 'slime' index relative to the control was 63%, 55%, 46%, 34%, 26% and 26% in the presence of 0.25, 0.5, 1, 2, 4, and 8 mg/mL of N-acetylcysteine, respectively. These data are statistically significant. The inhibitory effect of 2 mg/mL of N-acetylcysteine on slime formation was also verified by electron microscopy.

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Different criteria (the drug concentration which inhibited 50%Y of growth [IC1,2], the lowest drug concentration at which growth was just less than 30%o of that in a positive control well [IC301, the visual inhibitory concentration [ICJ], and the minimum fungicidal concentration [MFCl) were applied to study the effects of some antifungal agents against Candida albicans. Amphotericin B, flucytosine, and bifonazole produced total growth inhibition. Clotrimazole, itraconazole, ketoconazole, and miconazole produced partial growth inhibition. The values of IC,/2 and IC30 were similar for all agents and avoided the problems of partial inhibition; the values of ICv and MFC were higher than those of IC1/2 and IC30.The principal difficulty in interpreting susceptibility test results for antifungal agents is the partial growth inhibition produced by imidazole derivatives (10, 13). There is no unanimous agreement as to the best methodology for interpreting susceptibility test results (5,7,8,19,21). By the microdilution method, the inhibitory concentration (IC) is the lowest drug concentration that is capable of inhibiting a determined percentage of growth (10,12,13,16,(24)(25)(26), and an objective value for assessing the final point of inhibition is achieved. Turbidimetric methods can determine the minimum drug concentration which inhibits 50% of growth (IC112) (1,6,10,18) or the lowest drug concentration at which growth is just less than 30% of that in the positive control well (IC30) (12,13).In this study, the effects of increasing concentrations of seven antifungal agents on the growth of Candida albicans ATCC 10231 were studied. The ICs were also evaluated by comparing the criteria mentioned above (IC112 and IC30), the study of the visual inhibitory concentration (ICQ), and the minimum fungicidal concentration (MFC).The antifungal agents used in this study were amphotericin B (Squibb), clotrimazole and bifonazole (Bayer), miconazole (Isdin), itraconazole (Janssen) solubilized in dimethyl sulfoxide, flucytosine (Roche) resuspended in water, and ketoconazole (Janssen) solubilized in HCI (0.2 N). The concentrations of antifungal agents ranged from 0.01 to 40 ,ug/ml and were obtained by dilution in 0.01 M phosphate-buffered saline (PBS) at pH 7.C. albicans ATCC 10231 was grown in yeast nitrogen base medium (Difco) supplemented with 0.5% glucose in 0.01 M PBS (pH 7) (bYNBG).Growth kinetics, IC, and MFC studies were carried out in microtiter plates with a final volume of 200 ,ul. Each row of the microtiter plates contained the different concentrations of the antifungal agents and the strain tested. The final inoculum in each well was approximately 105 organisms/ml. Controls of sterility and growth without antifungal agents were carried out. Plates were incubated at 37°C in a humid atmosphere. At 0, 4, 12, 24, 48, and 72 h of incubation, the optical density (OD) at 492 nm was read in a Titertek * Corresponding author.Multiskan MC photometer. The data obtained after 24, 48, and 72 h were used to establish the IC1,2 and the I...

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The interaction of cefpirome and cefuroxime, with human polymorphonuclear leucocytes (PMNs) was examined. The effects of therapeutic concentration (1, 10, and 50 mg/L) of both antimicrobial agents on the adherence, spontaneous mobility, chemotaxis, chemokinesis, phagocytosis and candidacidal capacity were studied in vitro. No statistically significant variations, in relation to the control, were observed in the ability of PMNs to adhere to nylon fibre at the concentrations of cefuroxime and cefpirome used. With both antimicrobial agents, PMN mobility increased as the antibiotic concentration was increased. A statistically significant increase (P < 0.05) in spontaneous mobility, chemotaxis and chemokinesis was observed with cefpirome at only 10 mg/L. However, only spontaneous mobility was increased significantly with cefuroxime at 10 mg/L. The strongest effects were observed with cefpirome at 50 mg/L with variations of about 70% (P < 0.01), in chemotaxis and chemokinesis. In general, cefpirome had a positive effect on phagocytosis and candidacidal power, which was significant at a concentration of 50 mg/L (P < 0.01). Cefuroxime, in general, produced no modifications in either phagocytosis or candidacidal power.

The influence of various incubation atmospheres on the growth and slime production of 23 Staphylococcus epidermidis strains was studied. The atmospheres evaluated were aerobiosis (control), anaerobiosis, candle jar, 5% CO2 and 10% CO2. As compared to the aerobic control, growth was 55.7 +/- 19% (p < 0.01) in anaerobic incubation, 113.7 +/- 12% (p < 0.01) in 5% CO2, 112.8 +/- 13% (p < 0.01) in 10% CO2 and 106.4 +/- 7% (p > 0.1) in the candle jar. The slime production in relation to the aerobic control was 20.3 +/- 19% in anaerobiosis (p < 0.01), 22.3 +/- 27% (p < 0.01) in 5% CO2, 29.4 +/- 39% (p < 0.01) in 10% CO2 and 68.3 +/- 26% (p > 0.1) in the candle jar. The results of this study may explain the discrepancies which have been noted on occasion between slime formation data and pathogenicity.

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In vitro resistance of community-acquired and nosocomial strains of Enterococcus faecalis isolated in Badajoz (Spain) were determined by a microdilution method. The isolates were identified with conventional MicroScan Pos Combo 4 I dehydrated panels. No resistance to glycopeptides was found, but LY333328 was 2–4 times more active than vancomycin. In the nosocomial strains, high-level resistance to streptomycin (HLRS) was 54.7%, and high-level resistance to gentamicin (HLRG) was 38.1%. Resistance to ciprofloxacin and trovafloxacin was 45.3 and 38.9%, respectively. In the community-acquired isolates, HLRS, HLRG, resistance to ciprofloxacin and resistance to trovafloxacin were 44.2, 17.3, 15.4 and 13.5%, respectively. Trovafloxacin was 2–4 times more active than ciprofloxacin against both groups of strains. An association between high-level resistance to aminoglycosides and resistance to fluoroquinolones was noted. The resistance to aminoglycosides did not influence the activity of vancomycin and LY333328.