Masaru Satoh

Penetration of Ravuconazole, a New Triazole Antifungal, into Rat Tissues

Ravuconazole (BMS 207147, ER-30346) is a long-lasting triazole antifungal agent active against a broad spectrum of fungal pathogens including non-albicans Candida, Aspergillus, Cryptococcus and key dermatophytic fungi. The penetration of ravuconazole into rat tissues was examined. Fifty-five 7-week-old specific pathogen free female rats were used in this study. Plasma, lung and uterus tissue of rats were taken at 1, 2, 4, 8, 12, 16, 24, 32, 48, 60, and 72 h (n = 5) after oral administration of 10 mg/kg of ravuconazole. The quantitative assays of ravuconazole by HPLC after the extraction with diethylether were conducted for each tissue sample homogenate. tmax, t 1/2, and Cmax of ravuconazole is 8 h, 16.9 h and 1.68 µg/ml, respectively. The concentrations of ravuconazole in rat uterus and lung tissues were 2–to 6 times higher than the corresponding blood concentrations. The ratio of plasma to lung levels of ravuconazole was superior to the published data of other azoles. Considering its antifungal spectrum, ravuconazole would thus be a good candidate for treatment of deep-seated fungal infections caused by Candida, Aspergillus and Cryptococcus.

A Newly Designed Model for Infection-Induced Bladder Stone Formation in the Rat

A newly designed urolithiasis model for rats, inducing a mild urinary tract infection, exhibiting reduced renal damage without pyelonephritis and causing reliable stone formation, was established. This was accomplished by implanting a zinc disc in the bladder and then performing transvesical inoculation of Proteus mirabilis into the bladder. Five days after challenge with 10(7) colony forming units (CFU) of P. mirabilis in each rat, the number of organisms in the bladder urine reached a level of over 10(5) colony forming units per ml. The infection was mostly restricted to the urinary tract organs. Infectious bladder stones were formed 5 days after infection and developed day by day, weighing 88.3 +/- 18.8 mg. on the 21st day. Blood urea nitrogen values stayed in the normal range in all test animals during this experiment. The main composition of the stones formed was shown to be struvite (MgNH4PO4 X 6H2O).

Effect of ravuconazole, a new triazole antifungal, in a rat intraabdominal abscess model

Background: Ravuconazole (BMS-207147) is a long-lasting triazole antifungal agent active against a broad spectrum of fungal pathogens including non-albicans Candida, Aspergillus, Cryptococcus and key dermatophytic fungi. Methods: The efficacy of ravuconazole was evaluated using an experimental intraabdominal abscess model in rats caused by Candida albicans (E81022). Two hundred milligrams of cyclophosphamide per kilogram was injected intraperitoneally into 40 rats. Four days (96 h) after the injection of cyclophosphamide, a mixture of C. albicans and autoclaved rat cecal contents [C. albicans 1.7 × 108 colony-forming units/rat] was inoculated into the peritoneal cavity. The rats were divided into four groups: ravuconazole treated, fluconazole treated, itraconazole treated and untreated. Each antifungal was given orally at a dose of 10 mg/kg twice a day for 5 days. On the day after the last administration, the rats were dissected and the viable fungi in the abscesses were determined. The number of C. albicans in each abscess was determined by a quantitative culture technique. Results: Ravuconazole inhibited abscess formation and significantly decreased the viable cell counts in abscesses in comparison with the untreated group. It’s efficacy was at least equivalent to fluconazole and itraconazole against this pathogen. The rank order of potency (inhibition) was ravuconazole > itraconazole > fluconazole. Conclusion: Taking into consideration the antifungal spectrum of ravuconazole, which includes non-albicans Candida as well as C. albicans and Aspergillus, it is suggested that ravuconazole would be a good agent for the treatment of fungal peritonitis.

Effects of dietary calcium, magnesium and phosphorus on the formation of struvite stones in the urinary tract of rats

SummaryAfter feeding various diets we studied the effects of dietary calcium, magnesium and phosphorus on the formation of struvite stones in rats with urinary tract infections, and also studied the effects of the administration of vitamin D3 and aluminium gel on stone formation. A low-magnesium diet decreased urinary magnesium and prevented stone formation, but a medium-calcium diet did not significantly decrease stone weight. A high-calcium diet decreased urinary phosphorus and inhibited stone formation. A high-calcium and high-phosphorus diet decreased urinary excretion of magnesium and inhibited stone formation. Although the administration of vitamin D3 did not inhibit stone formation, aluminium gel decreased the urinary level of phosphorus and prevented stone formation. A marked decrease in urinary magnesium and/or phosphorus may prevent struvite stone formation in rats with urinary tract infections.

In vitro Bactericidal Activities of Antimicrobial Agents and Morphologic Changes on Prevotella bivia

Prevotella bivia is common in pelvic inflammatory diseases. Parenteral antimicrobial agents have been widely used against those infections. We investigated the bactericidal activities of three cephalosporins, i.e. cefluprenam (CFLP), ceftazidime (CAZ) and cefotaxime (CTX) and of two other antimicrobial agents, i.e. clindamycin (CLDM) and imipenem (IPM) against P. bivia. We also investigated the in vitro morphological changes induced by these agents in P. bivia. Cephalosporins exhibited bactericidal activities against P. bivia and induced time- and concentration-dependent morphological changes in P. bivia (filamentation). CLDM and IPM also had bactericidal activities, but induced different morphologic alterations: formation of spheroblasts and lysis. These results confirm the fact that each antimicrobial agent has characteristic aspects.

A new method for preparing electron microscopic specimens of Helicobacter pylori.

A new method for preparing electron microscopic specimens of Helicobacter pylori was developed and used to examine the ultrastructure of this bacterium. We have also investigated the morphological changes in the bacterium when exposed to amoxicillin using our new method. Bacterial specimens for electron microscopy are usually prepared by collecting the bacteria by centrifugation during the fixation and dehydration processes. In our new method the bacteria are filtered through and adsorbed onto a filter before fixation, and the entire filter containing the adhered bacteria is fixed and dehydrated. Using this method we were able to obtain electron photomicrographs in which the external appearances or internal structures of the bacteria were well conserved. The advantages of this method are that it uses only a small amount of bacterial suspension, shortens the time required for the dehydration procedure, and keeps the artifacts to the minimum. Amoxicillin treatment resulted in coccoid form with blebs in the bacterial surface and the appearance of vacuoles, granules, and an area of low electron density in the cytoplasm at one and four minimum inhibitory concentrations. These changes were consistent with results previously reported in the literature.

In vitro bactericidal activities of a new oral cephalosporin, E1100, and morphologic changes on Escherichia coli

Escherichia coli is one of the most common aerobic bacteria in pelvic inflammatory diseases. Oral cephalosporins have been widely used against those infections. We investigated in vitro morphologic changes induced on E. coli by a new oral cephalosporin, E1100, and its bactericidal activity on this organism. Morphologic changes were observed by electron microscopy. E1100 induced morphologic changes (filamentation) and exerted a bactericidal activity on E. coli. The filamentation induced by E1100 was time and concentration dependent.

Therapeutic effects of cefluprenam (CFLP) on polymicrobial infections associated with Enterococcus faecalis in rat pyometra model

Enterococcus faecalis plays an important role as one of the pathogens in polymicrobial infections. We evaluated the efficacy of cefluprenam (CFLP) using a polymicrobial pyometra of a model rat. Rats were infected with a mixed intrauterine inoculation of E. faecalis plus either Bacteroides fragilis or Prevotella bivia (minimal inhibitory concentration of CFLP: E. faecalis, 3.13 mug/ml; B. fragilis, 3.13 mug/ml; P. bivia, 3.13 mug/ml). Immediately after inoculating 10(5) cfu/rat of each organism, CFLP (either 40 mg/kg, i.v., q.i.d. for 5 days or 80 mg/kg, i.v., b.i.d. for 5 days) was administered. The intrauterine inflammatory change and bacterial count in the treated group were compared with those in the non-treated control group. CFLP significantly (P < 0.01) decreased the bacterial counts except for B. fragilis in the regimen of 80 mg/kg, b.i.d. However, the regimen of 40 mg/kg, q.i.d. significantly (P < 0.05) reduced the bacterial counts more than did that of 80 mg/kg, b.i.d. CFLP proved to demonstrate a good tissue concentration above 3 mug/g for 1 h. These results suggest that CFLP in a more divided dose is efficacious for the treatment of polymicrobial infections associated with E. faecalis in pyometra.

In vitro bactericidal activities and morphologic changes in Escherichia coli and Bacteroides fragilis by cephalosporins

Polymicrobial infections with aerobes and anaerobes are common in pelvic inflammatory diseases. New parenteral cephalosporins have been widely used against those infections. We investigated in vitro morphologic changes and bactericidal activities on Escherichia coli and Bacteroides fragilis by cephalosporins; cefluprenam (CFLP), ceftazidime (CAZ) or cefotaxime (CTX). CFLP induced morphologic changes (filamentation) and bactericidal activities on E. coli and B. fragilis. Morphologic changes were observed by electron microscope. The filamentation induced by CFLP was time and concentration dependent. The bactericidal activity of CFLP against E. coli was almost equal to those of CAZ and CTX. The bactericidal activity of CTX against B. fragilis was superior to those of CFLP and CAZ. These results suggest that there are characteristic aspects in each cephalosporin.

In vitro bactericidal activity and morphologic change in Bacteroides fragilis and Prevotella bivia with azithromycin

Abstract Objective The aim of the study was to investigate the in vitro bactericidal activity of azithromycin on Bacteroides fragilis and Prevotella bivia and the resulting morphologic changes in the 2 organisms. Background Azithromycin is an acid-stable, orally administered macrolide that is structurally related to erythromycin and has a spectrum of antimicrobial activity similar to that drug. Methods Bactericidal activity of azithromycin was determined by time-killing assays. Azithromycin-induced morphologic changes were observed by scanning electron microscopy of fragilis GOG3100 and P bivia GOG3120. Results Azithromycin showed bactericidal activity against fragilis at 4 times the minimum inhibitory concentration (MIC) and against P bivia at 1–2 times the MIC. No morphologic changes in fragilis and P bivia after azithromycin treatment were observed by electron microscopy; no filament ation, spheroblasts, or lysis were observed. Conclusion Although macrolides are not generally considered to be bactericidal, azithromycin showed bactericidal activity against the 2 organisms tested.