Postantifungal effect and effects of sub-MIC concentrations on previously treated Candida sp. influence of growth phase.

OBJECTIVES: This study evaluates the influence of growth phase on the postantifungal effect (PAFE) and on the effect of sub-MIC concentrations (1/4x MIC) on Candida sp. in PAFE stage (PAFSE). METHODS: This stage was induced by pre-treatments of 1.5 h of C. albicans or C. glabrata in their exponential or stationary phase, with 1x, 4x or 8x MIC of four antifungal agents that are fundamental for modern candidiasis therapy. RESULTS: Ketoconazole and fluconazole induced longer PAFSEs on microorganisms in logarithmic growth phase. However, this influence did not exist in the case of PAFSEs induced by AmB and 5-Fc or with the postantifungal effect induced by the four antifungal agents. In any way, significant PAFEs were always observed for Amphotericin B and 5-fluorocytosine (0.8-4.8 and 0.5-3 h, respectively, depending on the treatment dose). These values were increased (2.3-3.6 and 1.4-3.2 h respectively, depending on the pre-treatment dose) by posterior exposition to 1/4x MIC of the respective antifungal agent. In the case of ketoconazole and fluconazole, both antimycotics were not able to induce significant PAFEs, but posterior treatments to 1/4x MIC of each of the two azoles led in both yeast species to significant PAFSE of up to 2.6 h duration with ketoconazole, and 0.8 h with fluconazole, depending on the pre-treatment concentration. CONCLUSION: The growth phase of microorganisms should be considered in the planning of dosage protocols with azoles, because if the concentration applied is not high enough, the sub-MIC effects could be no significant for fungi in stationary phase of large wounds. Amphotericin B and 5-fluorocytosine induced significant postantifungal effect onCandida sp. This effect was increased by posterior exposition to sub-MIC concentration of the antifungal agents. Ketoconazole and fuconazole were not able to induce significant PAFEs at the concentrations tested, but posterior treatments to sub-MIC concentrations led to significant PAFSE. The growth phase of the culture at the time of its pre-treatment did not influence the length of the PAFE induced in it. However, the effect of the sub-MIC concentrations of Kz or Flu in yeast in PAFE phase was greater on yeast in exponential phase than for cultures in stationary phase.

Post-antifungal effect and effects of sub-MIC concentrations on previously treated Candida spp.: influence of exposure time and concentration.

This study evaluates the influence of exposure time and concentration on the post-antifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on Candida albicans and C. glabrata in the PAFE stage (PAFSE). This stage was induced by pretreatment for 1.5, 3 or 12 h with 1 x, 4 x or 8 x MIC of 4 antifungal agents fundamental to modern candidiasis therapy. The length of the 2 effects studied was dependent on the concentration of the antifungal agent applied during pretreatment, as well as on the exposure time. An increase in the dose and/or longer pretreatment prolonged the duration of the PAFE and PAFSE in both species and with all the antifungal agents. Significant PAFEs were always observed for amphotericin B and 5-fluorocytosine (0.8-13 h and 0.6-10.8 h, respectively). These values were increased (by 2.3-8.7 h and 1.5-7.8 h, respectively) by posterior exposure to 1/4 x MIC of the respective antifungal agent. Neither ketoconazole nor fluconazole were able to induce significant PAFEs, even with exposures of up to 12 h duration and a dose of 8 x MIC. However, treatment with 1/4 x MIC of each of the 2 azoles led to significant PAFSEs in both yeast species, of up to 6.5 h duration with ketoconazole and 1.7 h with fluconazole, if the concentrations and/or exposure times were sufficiently high.

Maturing wines in oak barrels. Effects of origin, volume, and age of the barrel on the wine volatile composition.

The influence of the oak origin, volume, and age of the barrel on the volatile composition of a red wine after six months of maturation have been studied. Major volatile compounds in wine were determined using liquid-liquid extraction with dichloromethane, and those volatiles being due to the oak were determined by extraction with pentane-ether using deuterated analogues as internal standards. The results show that there is little difference between the volatile composition of wines matured in French oak barrels and those matured in American oak barrels. The concentration of cis-oak lactone was the most significant difference. The greatest instrumental and sensory differences were found between new and used barrels, with important decreases in lactones and vanillin concentration in used barrels. When studying the effect of the volume of the barrel, the characteristics of the wine matured in 220-L new barrels versus those matured in 1000-L new barrels were very different. In new barrels, the larger the volume of the barrel, the lower the concentrations of those compounds responsible for the oaky aroma. These differences were less evident when comparing wines matured in used barrels with different capacities.

Influence of temperature and concentration on the postantifungal effect and the effects of sub-MIC concentrations of four antifungal agents on previously treated Candida species.

BACKGROUND: The objective of this study was to investigate the impact of different temperatures (22, 35 and 37 degrees C) on the postantifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on Candida albicans and Candida glabrata in PAFE stage (PAFSE). METHODS: This stage was induced by a 1.5-hour pretreatment with different doses (1 x, 4 x and 8 x MIC) of four antifungal agents that are fundamental to modern candidiasis therapy. RESULTS: The temperature, as well as the dose of the antifungal agent that was applied during the pretreatment, determined the duration of the two studied effects. An increase in the temperature and/or the dose prolonged the duration of the PAFE and PAFSE in both species, independent of the applied antifungal agent. Amphotericin B and 5-fluorocytosine always induced significant PAFEs (0.5-4.8 h and 0.5-3.0 h, respectively), which were increased (0.7-3.4 h and 0.5-3. 2 h, respectively) by posterior exposure to 1/4 x MIC of the respective antifungal agent. In the case of ketoconazole and fluconazole, temperature and concentration were especially important. Although neither antimycotics was able to induce a significant PAFE, posterior exposure to 1/4 x MIC of each of the two azoles led in both yeast species to a significant PAFSE of up to 0.8 h (if the concentrations and/or the temperatures were high enough). CONCLUSION: Factors such as temperature and concentration could be important when choosing an antifungal agent.

Influence of pH and concentration on the postantifungal effect and on the effects of sub-MIC concentrations of 4 antifungal agents on previously treated Candida spp.

This study investigates the impact of different pH values (5.5 and 7.4) on the postantifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on C. albicans and C. glabrata in the PAFE stage (PAFSE). The PAFE stage was induced by a 1.5 h pretreatment with different doses (1, 4 and 8 x MIC) of 4 antifungal agents. An increase in the pH and/or an increase in the dose of the antimycotic prolonged the duration of the PAFE induced by amphotericin B or 5-fluorocytosine and the PAFSE induced by all 4 antifungal agents in both species. 5-Fluorocytosine and amphotericin B (except for treatment with 1 x MIC at pH 5.5) induced significant PAFEs (0.5-3.0 h and 1.4-4.8 h, respectively), which were increased (to 0.9-3.2 h and 0.8-3.4 h, respectively) by posterior (PLEASE EXPLAIN WHAT YOU MEAN BY THE WORD "POSTERIOR" HERE) exposure to 1/4 X MIC of the respective antifungal agent. Although ketoconazole and fluconazole were not able to induce significant PAFEs, posterior exposure to 1/4 x MIC of each of these 2 azoles led to significant PAFSEs of up to 2.6 h in both yeast species when the concentrations and pH were high enough.

Activity of voriconazole: post-antifungal effect, effects of low concentrations and of pretreatment on the susceptibility of Candida albicans to leucocytes.

This study examined: (i) the post-antifungal effect (PAFE) of Voriconazole (UK 109,496) on Candida albicans, at 2 concentrations (MIC and 4 x MIC) in the presence or absence of 10% human serum; (ii) the activity of low concentrations of the drug (1/4 x MIC) on yeasts that had previously been exposed to Voriconazole (PAFSE) with or without 10% human serum; and (iii) the effect of Voriconazole pretreatment on the fungicidal activity of leucocytes and serum against C. albicans (PALE). Two concentrations (0.25 and 1 mg/l) of Voriconazole induced no PAFE against C. albicans between -4.3 and -1.4 h, but when the assays were performed in the presence of serum, positive and concentration-dependent PAFEs were obtained (0.2-4.1 h). Pretreated yeasts were more susceptible than untreated yeasts to low concentrations (0.0625 mg/l) of Voriconazole, so the drug showed positive PAFSE that was dependent on the concentration used in pretreatment without serum (0.3-1.9 h) or with 10% human serum (0.5-2.5 h). Pretreatment of the growing C. albicans cells with Voriconazole (0.25 mg/l) increased their vulnerability to killing by leucocytes during the last 2 h (p < 0.05), leading to PALE of 2 h. The results suggest that these effects might be used to evaluate the in vivo activity of an antifungal agent. The sum of the durations of these effects (PAFE, PAFSES and PALE) cause a considerable delay in yeast growth in treated cultures compared with control cultures.

[Descriptive study of complications caused by mediastinoscopy]. / Estudio descriptivo de las complicaciones de la mediastinoscopia.

To analyze the surgical and non surgical complications of mediastinoscopy in a series of 200 consecutive patients. Retrospective study of all surgical patients between 1 January 1994 and 1 May 1997. Any complication presenting between time of surgery and patient release is analyzed. Complications were seen in 8 out of 200 cases (4%). In three cases, there were lesions in neighboring structures (recurrent nerve, bronchial artery and innominate artery). The rest were non surgical complications (3 cases of arrhythmia, 2 of prolonged mechanical ventilation). One male patient (0.5%) died from cerebral infarction, probably as a result of arterial occlusion needed to suture damage to the innominate artery. Superior win cava syndrome affected 20% (1 in 5) and morbidity was 60% (3 in 5). Morbidity involving both medical and surgical complications in this series is higher than that reported elsewhere in the literature, in series for which non surgical complications go unreported.

Effects of antifungal pretreatment on the susceptibility of Candida albicans to human leukocytes.

The aim of this work was to measure the susceptibility of Candida albicans pretreated for 2 or 6 h with fluconazole (Flu), ketoconazole (Ktz), amphotericin B (AmB) and 5-fluorocytosine (5-Fc) to the fungicidal action of human polymorphic leukocytes. The influence of pretreatment was measured by comparing the delay (in hours) and reduction (log10) in growth of pretreated cultures in the presence of leukocytes and serum with that of non-pretreated control cultures. Six-hour pretreatments with Flu, Ktz, AmB and 5-Fc led to growth delays of 1, 3, 3 and 3 h, respectively. No significant differences were found when pretreatment lasted only 2 h. With respect to a reduction in growth, this was larger when the preincubation was 6 h, mainly for 5-Fc and AmB. 5-Fc was seen to be the most effective, followed by Ktz, AmB and finally Flu. It may be concluded that antifungal pretreatment renders this yeast more susceptible to the action of leukocytes. The degree of susceptibility achieved is dependent on the antifungal agent employed.

Influence of human serum on the postantifungal effect of four antifungal agents on Candida albicans.

This study evaluates the influence of both fresh and heated human serum on the postantifungal effect (PAFE) induced by different concentrations of amphotericin B (AmB), 5-fluorocytosine (5-Fc), Ketoconazole (Kz) and fluconazole (Flu) on two strains of Candida albicans. The concentrations were selected in harmony with the pharmacokinetic properties and toxicity of the drugs. Without serum there was no delay in the growth of yeast cultures pretreated with Kz or Flu, leading to negative PAFEs, however with AmB and 5-Fc the PAFEs were positive. When assays were made in the presence of 10% fresh human serum, the duration of the PAFEs increased with all drugs tested, and those induced by azolic agents became positive. In the presence of 10% human serum heated at 56 degrees C for 30 min, the PAFEs of the antifungal agents were similar to those obtained in the absence of serum. Our results suggest that fresh serum positively influenced PAFE which may be an important factor in determining the dosing regimen for infection by yeasts.

Postantifungal effect and effects of low concentrations of amphotericin B and fluconazole on previously treated Candida albicans.

The objective of the study was to assess (a) the postantifungal effect (PAFE) of amphotericin B (AmB) and fluconazole (Flu) on two Candida albicans strains, and (b) the effect of low concentrations of AmB or Flu on yeasts previously exposed to AmB or Flu, respectively, in the presence or absence of 10% human serum. In the absence of serum, AmB exerted a positive effect (at 0.5-5.0 h) depending on the concentration and the strain used. Flu, however, produced negative effects (at -1.2 to -0.1 h). When the experiment was conducted in the presence of serum, the duration of all PAFEs increased significantly, especially those induced by Flu that became positive. Pretreated yeasts were more susceptible than untreated controls to the antifungal activity of low concentrations of the drugs. Growth delay was more pronounced with Flu (up to 5.2 h), whereas the greatest decrease in log10 at 12 h was slightly more pronounced for AmB. A knowledge of PAFEs and the effects of low drug concentrations on pretreated yeasts and the effects of serum on these is important in order to gain more insight into the in vivo activity of the study drugs.

Activity of fluconazole: postantifungal effect, effects of low concentrations and of pretreatment on the susceptibility of Candida albicans to leucocytes.

Exposure times and serum concentrations in humans after treatment with multiple doses of fluconazole have been studied to measure: (a) the postantifungal effect (PAFE) on Candida albicans, at two concentrations of the drug in the presence or absence of 10% human serum; (b) the activity of low concentrations of the drug on yeasts previously exposed to fluconazole with or without 10% human serum; and (c) the effect of fluconazole pretreatment on the fungicidal activity of leucocytes and serum against C. albicans. Fluconazole showed no PAFE against C. albicans between -0.1 and -0.7 h, but when the assays were performed in the presence of serum, concentration dependent PAFEs were obtained (1.1 h-3.6 h). Pretreated yeasts were more susceptible than untreated yeasts to low concentrations of the drug. The decrease in growth was dependent on the concentration used in pretreatment. Growth delay was also more marked when the yeast cells were tested in the presence of serum. Pretreatment of the growing C. albicans cells with fluconazole increased their vulnerability to killing by leucocytes mainly in the first hour (P < 0.05). These results could partially explain why fluconazole has more activity in vivo than in vitro.

H7, an inhibitor of protein kinase C, inhibits tumour cell division in mice bearing ascitic Ehrlich's carcinoma.

We have previously shown that H7, an inhibitor of protein kinase C (PKC), inhibits proliferation of several cell lines as well as of primary cultured cells from human tumours. The aim of this work was to assess whether H7 is able to prevent the division of tumour cells in mice bearing Ehrlich's ascitic carcinoma. The LD50 of H7 injected intravenously was 61 mg/kg and 94 mg/kg for starved and fed mice, respectively. Acute intraperitoneal injection of 100 mg/kg of H7 decreased the number of mitoses in tumoral cells from ascitic fluid of mice bearing the carcinoma. The reduction was maximal (approximately 50%) after 90 min and then the number of mitosis rose due to a decrease in H7. Continuous delivery of H7 from mini-osmotic pumps implanted on the backs of the mice reduced the number of mitoses by approximately 65%, and the effect was maintained for approximately 24 h. The effect cannot be maintained for longer because H7 is unstable at body temperature. These results indicate that inhibition of PKC can block division of tumour cells in carcinoma-bearing animals, and support the idea that inhibitors of PKC could be useful for the clinical control of proliferation of certain tumours.

In vitro killing kinetics and postantibiotic effect of josamycin and other macrolides on several bacteria.

The antimicrobial activity [minimal inhibitory concentration (MIC) and killing kinetics] and postantibiotic effect (PAE) of different concentrations (MIC and 10 x MIC) of josamycin, erythromycin, midecamycin and azithromycin on Streptococcus pneumoniae, Staphylococcus aureus and Escherichia coli were studied in vitro. The MIC and killing kinetics were determined by standard methods. The PAE was measured after 1 h exposure to the drugs, which were removed by diluting the culture 1,000-fold. All tested macrolides had their lowest MIC against S. pneumoniae, and the most active against S. aureus was josamycin. In killing kinetics, using 10 x MIC, the macrolides exhibited a bactericidal effect against S. pneumoniae and E. coli, with reductions of 3 log10 in colony-forming units per milliliter with respect to the initial inoculum, while a bactericidal effect was not observed for S. aureus. The PAEs were concentration dependent, the greatest PAEs being obtained with S. pneumoniae. Although lower, the PAEs induced on E. coli were significant when high concentrations of the drug were tested. The assayed macrolides showed both more activity and PAEs on S. pneumoniae.

In vivo postantibiotic effect of isepamicin and other aminoglycosides in a thigh infection model in neutropenic mice.

The object of this work is to study in neutropenic mice the in vivo postantibiotic effect (PAE) of isepamicin, a new aminoglycoside, gentamicin and netilmicin on Staphylococcus aureus and Escherichia coli and in vivo killing kinetics using two different schedules (A and B) of isepamicin and gentamicin administration against S. aureus: (A) at time zero and every hour up to the 7th or 9th hour and (B) two doses only, at time zero and at the end of the PAE. The PAE of the three aminoglycosides was long (3-5 h), showing that of isepamicin to be the largest, especially on S. aureus. Both A and B treatment models show the same effectiveness for the two tested drugs. These results support the idea that the major significance of the PAE is in its application to dosing regimens.

Postantibiotic effect of ciprofloxacin compared with that of five other quinolones.

The antimicrobial activity (minimal inhibitory concentration, MIC, and killing kinetics) and postantibiotic effect (PAE) of different concentrations (MIC and 6 mg/1) of ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, fleroxacin and lomefloxacin on pure cultures of Staphylococcus aureus and Escherichia coli were compared in vitro. The MIC, killing kinetics and PAE were determined by standard methods. Ciprofloxacin displayed the lowest MICs, while the highest were those of norfloxacin against S. aureus and lomefloxacin against E. coli. The killing curves showed ciprofloxacin to be the most and norfloxacin the least active. The bactericidal power was dependent on the concentration. At MIC, the fluoroquinolones, with the exception of norfloxacin, induced PAEs of 1-2 h. The effect was, in all cases, greater against E. coli. When assayed at 6 mg/l the PAEs were increased to 2-5 h, the best results being obtained by ciprofloxacin followed by ofloxacin. Norfloxacin produced no PAE on S. aureus and scarcely reached 1.3 h against E. coli. There was a close relationship between bactericidal power and PAE.

[Antimicrobial activity of ozonized water in determined experimental conditions]. / Actividad antimicrobiana del agua ozonizada en determinadas condiciones experimentales.

Ozone is a potent disinfecting agent which has been used successfully in water treatment, as well as to cure wounds. It can also be used in dental clinics, in laboratories, and in hospitals to clean and disinfect work surfaces and instruments. In this paper we have carried out a study of the antimicrobial activity of ozonized water. Antimicrobial activity in ozonized water on bacterial suspensions and contaminated materials was meaningful and depended fundamentally on concentration and time of exposure. On buccal flora, one rinse alone had no effect, but various successive rinses led to substantial reductions in the number of colonies of bacteria. Ozone had a similar effect, although more pronounced, on the flora of the hands. Ozonized water placed in an open dish kept up antimicrobial activity for the first 20 minutes, but after 30 minutes this activity decreased substantially.

[Influence of bacterial combinations on the post-antibiotic effect]. / Influencia de las asociaciones bacterianas sobre el efecto postantibiótico.

A study of the post-antibiotic effect (PAE) and letality curves of different concentrations of clavulanic acid, amoxycillin, amoxycillin + clavulanic acid, netilmycin and ofloxacin on mixed cultures of S. aureus and E. coli. The post-antibiotic effect was measured after one hour of exposure of bacteria to antimicrobial and the elimination of the latter by the dilution method. Amoxycillin did not induce PAE on the association. PAE only appeared at high concentrations on S. aureus when evaluated alone. Clavulanic acid induced a greater PAE than amoxycillin. The association clavulanic acid + amoxycillin was synergistic and induced a greater PAE than its components. Netilmycin and ofloxacin were the drugs that induced the greatest PAE on the bacterial association and on its strains independently evaluated.