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The mechanism of fungitoxic action of an antifungal antibiotic benanomicin A was studied with intact cells and protoplasts of Saccharomyces cerevisiae as well as with its enzymic preparations. The results obtained are summarized as follows: (1) benanomicin A at relatively high concentrations (almost equal to MIC) was fungicidal and disrupted the cell permeability barrier, inducing leakage of intracellular K+ and ATP in growing cells, while the antibiotic had none of these effects in non-growing cells; (2) no biosynthesis of any of several major cellular constituents in yeast cells was inhibited markedly or selectively enough to explain its fungitoxic activity; (3) whereas benanomicin A induced lysis of metabolically active yeast protoplasts incubated in the presence of glucose, inactive yeast protoplasts incubated without glucose were refractory to the lytic action of the antibiotic; (4) osmotically shocked yeast cells became feasible to the cidal action of benanomicin A; (5) benanomicin A substantially inhibited uptake of 6-deoxy-glucose by yeast cells; (6) liposomes composed of phospholipids and cholesterol were not susceptible to benanomicin A; and (7) benanomicin A inhibited in vitro activity of H(+)-ATPase from yeast cell membranes to a greater extent than that for H(+)-ATPase from yeast mitochondria or H(+)-ATPase from yeast vacuolar membranes. Based on these and our previous data that benanomicin A preferentially binds to mannan or mannoproteins constituting the cell wall and cell membrane of yeasts, such binding of the antibiotic is suggested to deteriorate the normal structure and function of those cell membranes of yeasts which are in a growing or metabolically active state, ultimately leading to cell death.

A new antitumor antibiotic SF2575 has been isolated from a culture filtrate of Streptomyces sp. SF2575. The molecular formula was determined to be C40H43NO15 by elemental analysis, mass and 13C NMR spectral analyses. The spectral data revealed SF2575 to be a new tetracycline antibiotic. It was active against Gram-positive bacteria and exhibited antitumor activity against P388 leukemia in mice.

We examined the effects of fosfomycin (FOM), norfloxacin (NFLX), kanamycin (KM), chloramphenicol (CP), and ampicillin (ABPC) on the morphology of E. coli O157:H7, and the accumulation (cell fraction) and release (medium fraction) of Shiga toxins (Stxs: Stx1 and Stx2) in E. coli O157:H7 three hours after treatment with the antibiotics. For each drug, 16 MIC was used for measurement of the activity at a high drug concentration and 1/4 MIC at a low concentration. At 16 MIC, cell wall synthesis inhibitors, FOM and ABPC, strongly induced lysis of the cell of E. coli KU3342, a strain of E. coli O157:H7. The release of Stx1 was observed, but there was no accumulation of Stxs. Nucleic acid synthesis inhibitor NFLX and protein synthesis inhibitor KM induced partial lysis and short filamentation of the cell, and the accumulation and release of Stxs were low. No morphological change was observed after treatment with protein synthesis inhibitor CP, but the accumulation and release of Stxs by CP were low. At 1/4 MIC, FOM induced strong lysis of the cell, and the release of Stx1 was observed, but there was no accumulation of Stxs. ABPC and NFLX had weak lytic reaction, but induced filamentation of the cell, and the accumulation and release of Stxs were observed. In particular, NFLX significantly induced accumulation and release of Stx2. KM and CP had no effect on the morphology of the cells, and the accumulation of Stx1 was not observed, but there was no release of Stxs. The above-mentioned results support the clinical efficacy of FOM in the control of enterohoemorhagic E. coli infections.

Pharmacokinetic and pharmacodynamic (PK/PD) parameters, which are important indices of the therapeutic efficacy of antimicrobials, and the minimum inhibitory concentration (MIC) predictive of clinical efficacy at common clinical doses, were examined for biapenem (BIPM; 300 mg b.i.d.), imipenem/cilastatin (IPM/CS; 500 mg/500 mg b.i.d.), meropenem (MEPM; 500 mg b.i.d.), and ceftazidime (CAZ; 1000 mg b.i.d.), using a mouse model of thigh infection caused by Pseudomonas aeruginosa. The PK/PD parameter that most closely correlated with the therapeutic efficacy of all these antimicrobials was time above MIC (TMIC). The values of TMIC predictive of clinical efficacy against P. aeruginosa infection varied among antimicrobials and were/=17%,/=17%,/=23%, and/=33% for BIPM, IPM/CS, MEPM, and CAZ, respectively. From these values and the known plasma concentrations of the antimicrobials in humans after administration at the common clinical doses, the MIC for bacterial strains at which clinical efficacy can be expected was estimated to be/=4.4 microg/ml for BIPM,/=6.1 microg/ml for IPM/CS,/=2.2 microg/ml for MEPM, and/=13.6 microg/ml for CAZ. These MICs nearly coincided with the MIC(80) of the antimicrobials for 104 clinical isolates of P. aeruginosa strains. These results indicate that, even at a low dose, of 300 mg b.i.d., the clinical efficacy of BIPM against P. aeruginosa infection can be expected to be comparable to that of IPM/CS, MEPM, and CAZ.

Antibacterial activity of biapenem (BIPM) against clinical isolates of 8 species between 2000 and 2002 was compared with those of imipenem/cilastatin (IPM/CS), meropenem (MEPM), panipenem/betamipron (PAPM/BP) and ceftazidime (CAZ). The MICs of biapenem for Gram-positive bacteria were higher than those of IPM/CS and PAPM/BP, equal to those of MEPM and lower than those of CAZ. The MICs of BIPM for Gram-negative bacteria were higher than those of MEPM, equal to those of IPM/CS and PAPM/BP, and lower than those of CAZ. Antibacterial activity of BIPM against Pseudomonas aeruginosa was equal to those of IPM/CS and MEPM and superior to those of PAPM/BP and CAZ. In conclusion, BIPM showed broad antibacterial activity against both Gram-positive and Gram-negative clinical isolates. These results suggest that BIPM is useful for the treatment of various bacterial infections.

PF1163A and B are a pair of antifungal agents isolated from a fermentation broth of Penicillium sp. PF1163A inhibited ergosterol synthesis in Saccharomyces cerevisiae, resulting in an accumulation of 4,4-dimethylzymosterol and a decrease of ergosterol. The ERG25 strain overexpressing the ERG25 gene was resistant to PF1163A. ERG25p is a C-4 sterol methyl oxidase known to be essential for the viability of yeast and fungi because of the known role of ERG25 gene disruption in S. cerevisiae-led lethality. ERG25p is the enzyme responsible for the first step in the removal of the two methyl groups at the C-4 position of sterol. From the results obtained here, we conclude that PF1163A is a novel natural antifungal that inhibits C-4 sterol methyl oxidase.

In vitro antibacterial activity of fosfomycin was evaluated by various methods. Strains of methicillin-sensitive Staphylococcus aureus, methicillin-sensitive coagulase-negative Staphylococci and Escherichia coli were much more susceptible when glucose-6-phosphate was added to the test medium, but strains of Serratia marcescens and Pseudomonas aeruginosa were not affected. Nutrient agar instead of Mueller-Hinton agar allowed to exhibiting the higher activity of fosfomycin against all the species tested. The activity of fosfomycin was as equivalent or superior to those of cefazolin, cefmetazole, cefotiam and piperacillin. The susceptibility of strains isolated during 2000 to 2001 to fosfomycin was almost the same as that of the isolates reported in 1975. Fosfomycin was considered to show high efficacy in several infections, since it has maintained its favorable antibacterial activities against several bacterial species for more than 20 years after the first application to clinical practice.

The in vitro short-term bactericidal activity and accumulation of NM394, the active metabolite of prulifloxacin, was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX), using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Of the 4 fluoroquinolones examined, NM394 accumulated to the highest concentration in all three strains. The order of concentration of the fluoroquinolones accumurated in S. aureus 209P JC-1, E. coli NIHJ JC-2 and P. aeruginosa PAO1 were NM394CPFXGFLXor = LVFX. The accumulation of fluoroquinolones into bacterial cells correlated with their MICs of the drugs for E. coli and P. aeruginosa, whereas there was no correlation between the accumulation and MICs of the drugs for S. aureus. We also studied the reduction of viable cells after addition of each fluoroquinolones to clarify relationship between the short-term bactericidal activity and the accumulation of the quinolones. The short-term bactericidal activity of NM394 against S. aureus 209P JC-1, E. coli NIHJ JC-2 and P. aeruginosa PAO1 were stronger than those of CPFX, LVFX and GFLX when compared at the same concentration. In conclusion, the strong short-term bactericidal activity of NM394 may be attributed to its high accumulation in bacterial cells.

The inhibitory activity of NM394, the active form of the prodrug prulifloxacin, against type II topoisomerase from Pseudomonas aeruginosa was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX). The 50% inhibitory concentrations (IC50S) of NM394 for supercoiling activity of DNA gyrase and the decatenation activity of topoisomerase IV were 1.21 and 21.1 micrograms/ml, respectively. The IC50 of NM394 was equal to that of CPFX and lower than those of LVFX and GFLX. The inhibitory activity of the four drugs for DNA gyrase was also corresponding to the antimicrobial activity of the drugs for P. aeruginosa PAO1. The IC50S of the drugs tested for the decatenation activity of topoisomerase IV were from 17.4 to 24.2 times higher than those for the supercoiling activities of DNA gyrase. These results show that DNA gyrase is more sensitive to quinolones than is topoisomerase IV and may be a primary target of quinolones in P. aeruginosa. We concluded that NM394 exerts the potent antimicrobial activity through its strong inhibitory activity for DNA gyrase.

Benanomicin A showed a broad antifungal spectrum, inhibiting the growth of all test strains of 41 yeasts, 23 dimorphic fungi, 23 dematiaceous fungi, 16 aspergilli, and 19 dermatophytes, with the exception of 12 zygomycetic strains. The MIC values of benanomicin A were comparable to those of amphotericin B against Cryptococcus. Rhodotorula, Trichosporon, Geotrichum, Sporothrix, and some dermatophytes, but were two to eightfold higher than those of amphotericin B against other fungal pathogens tested. The action of benanomicin A was fungicidal.

Benanomicin A is an antifungal antibiotic produced by Actinomadura spadix. In the present study, we investigated the effect of benanomicin A on the phagocytosis of Candida albicans by murine peritoneal macrophages and on the cell-surface hydrophobicity (CSH) of C. albicans. Although pretreatment of macrophages with benanomicin A had no effect on the phagocytosis, addition of benanomicin A to the culture of macrophages and Candida cells increased the susceptibility of Candida cells to the phagocytosis by the macrophages. Pretreatment of Candida cells with benanomicin A also increased the susceptibility of Candida cells to the phagocytosis. When Candida cells were mixed with benanomicin A, the antibiotic bound irreversibly to Candida cells. These data suggest the possibility that the increased susceptibility of Candida cells to the phagocytosis is mediated by the binding of benanomicin A to Candida cells. Examination of physicochemical property of Candida cell surface showed that the CSH of Candida cells significantly decreased by the treatment with benanomicin A. Thus, binding of benanomicin A to Candida cells may induce biochemical/physicochemical alternation of the surfaces, so that they become more susceptible to phagocytosis by murine macrophages. These properties of benanomicin A, along with its antifungal activity, seem to be beneficial in the treatment of fungal infections.

A new antibiotic SF2487 has been isolated from the culture broth of Actinomadura sp. SF2487. The structure of antibiotic SF2487 was determined by spectroscopic analyses of the sodium salt and X-ray diffraction analysis of the silver salt. The antibiotic represents a new member of polyether group antibiotics known as the acyltetronic acid type 4. The antibiotic is weakly active against Gram-positive bacteria and exhibits antiviral activity against influenza virus in vitro.

A new species of Streptomyces is described for which the name Streptomyces aculeolatus is proposed. The organism produces new antibiotics SF2415A1, A2, A3, B1, B2 and B3 active against Gram-positive bacteria. Empirical molecular formulae of the antibiotics SF2415A1, A2, A3, B1, B2 and B3 were determined to be C26H31N2O5Cl, C26H30N2O5, C26H30N2O5Cl2, C26H33O5Cl, C26H32O5 and C26H32O5Cl2, respectively.