Takuji Nakashima

Egg lecithin greatly reduced the antibacterial activities of chlorhexidine gluconate (CHG). By using this antagonistic action, slower‐growing bacteria, for which a longer incubation time was needed for its growth, were isolated from marine soils. The growth of relatively faster‐growing bacteria, which formed visible colonies during a 3 day incubating period, was significantly inhibited by treatment with 8 µg of CHG per mL for 10 min, whereas the addition of egg lecithin to a final concentration of 2%, after the treatment, had no significant effect on the viability of slower‐growing bacteria.

Background Reactive oxygen species (ROS) released from inflammatory cells constitute one of the critical causative factors in inflammatory skin diseases such as seborrhoeic dermatitis and atopic dermatitis. Objectives To investigate inhibitory effects of ketoconazole (KCZ) and ciclopiroxolamine (CPO), both of which have been used for the treatment of seborrhoeic dermatitis, on ROS released from inflammatory cells. Methods The methyl‐Cypridina‐luciferin analogue‐dependent chemiluminescence method was employed for the detection of ROS production by phorbol 12‐myristate 13‐acetate (PMA)‐stimulated inflammatory cells. Moreover, the radical scavenging activities of both agents were examined by using a hypoxanthine–xanthine oxidase system and the stable radical 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH). NADPH oxidase activity was determined in particulate (membrane) fractions prepared from PMA‐stimulated RAW 264·7 cells, a macrophage‐like cell line. Results Both of these antifungal agents inhibited PMA‐stimulated ROS production. However, only CPO significantly scavenged both ROS generated by the hypoxanthine–xanthine oxidase system and DPPH, and the scavenging activity of CPO seemed to act on ROS other than superoxide anions. Although KCZ inhibited PMA‐stimulated ROS production, it did not show radical‐scavenging activities. The inhibition of ROS production by KCZ is probably attributable to the inhibition of NADPH oxidase activity. Conclusions The mechanism of the inhibitory action of KCZ against PMA‐stimulated ROS production is distinct from that of CPO. Knowledge of the inhibitory or scavenging effects of both antifungal agents on ROS released from inflammatory cells may be useful in developing a therapeutic strategy for dermatitis.

Recently we discovered a bacterial strain (MS‐02–063) that produces large amounts of red pigment from coastal area of Nagasaki Prefecture, Japan. Comparative 16S rDNA gene sequencing analysis revealed that strain MS‐02–063 was phylogenetically closely related to γ‐proteobacterium Hahellasp. MBIC 3957 that produces prodigiosin. However, some physiological and biochemical differences between strain MS‐02–063 andHahellasp. MBIC 3957 were observed. The red pigment (RP‐063) produced by this isolate was highly purified from the culture supernatant. It was speculated that RP‐063 might be prodigiosin‐like pigment in physical properties and biological activities such as antibacterial and cytotoxic activity. Antibacterial activity of RP‐063 was examined by an agar dilution method. The results indicated that RP‐063 showed antibacterial activity for specific for pathogenic gram‐positive bacteria such asStaphylococcus aureus. The potency of antibacterial activity againstS. aureuswas nearly equal to those of tetracycline. Moreover, RP‐063 showed inhibition of the superoxide generation by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA)‐stimulated mouse macrophage RAW 264.7 cell line. Prodigiosin members have a wide variety of biological properties, including anticancer and antimalarial, etc. Especially, potent immunosuppressive properties have been reported for prodigiosin members with the mechanism of action different from that of the other well known immunosuppressors in atopic dermatitis therapy such as cyclosporin A, FK506 and rapamycin. It is suggested that RP‐063 may be able to arrest the inflammation caused by superantigens secreted fromS. aureus, which colonized skin on atopic dermatitis as well as suppression of activated lymphocyte proliferation and superoxide generation from leucocytes.

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Antifungal susceptibility testing under conditions close to clinical status is expected to provide more helpful information than that obtained by a conventional microdilution method. For this purpose, we developed a novel method to evaluate anti-Trichophyton mentagrophytes activity of antifungal agents in vitro by using disks of micropig stratum corneum epidermis (SCE). Basal agar medium containing K2HPO4, MgSO4, CaCl2 and three kinds of antibiotics. Bifonazole (BFZ), lanoconazole (LCZ) or terbinafine (TBF) was added to the basal agar medium to give serially doubling dilutions ranging from 0.0006 to 10 microg/ml. Five-hundred-microl portions of the agar media thus prepared were solidified in wells of flat-bottomed plates. SCE disks (6 mm in diameter) were placed on surfaces of the agar medium and 10(4) conidia of T. mentagrophytes were inoculated on each SCE disk. There was very good correlation between the initial concentration of the antifungal agents added to the basal agar medium (microg/ml) and the concentration of the agents impregnated into the SCE disks (microg/g) (r2>0.99). The minimum inhibitory concentration (MIC) values of BFZ, LCZ and TBF were respectively 26-, 10- and 78-times higher than those measured by the standard microdilution method. From the correlation between the concentration of the agents in the basal medium and that in the SCE disks, the above MIC values corresponded to the concentrations in SCE disks (microg/g), 832.95 for BFZ, 1.42 for LCZ and 8.87 for TBF. This novel method of antidermatophytic susceptibility testing using SCE would be useful as an in vitro screening of proper antimycotics for topical treatment of dermatophytosis.