Cyslabdan, a new potentiator of imipenem activity against methicillin-resistant Staphylococcus aureus, produced by Streptomyces sp. K04-0144. II. Biological activities

Cyslabdan produced by Streptomyces sp. K04-0144 was found to potentiate imipenem activity against methicillin-resistant Staphylococcus aureus (MRSA). The MIC value of imipenem against MRSA was reduced from 16 to 0.015 microg/ml in combination with cyslabdan. Study on anti-MRSA activity of other typical antibiotics in combination with cyslabdan showed that the potentiating activity was limited to beta-lactam antibiotics. Furthermore, among beta-lactam antibiotics, the activity of carbapenems was most remarkably potentiated by cyslabdan.     

Arborcandins A, B, C, D, E and F, novel 1,3-beta-glucan synthase inhibitors: production and biological activity

Arborcandins A, B, C, D, E and F, which possess potent 1,3-beta-glucan synthase inhibitory activity, were isolated from the culture broth of a filamentous fungus, strain SANK 17397. Arborcandins are novel cyclic peptides, that are structurally different from known glucan synthase inhibitors such as echinocandins. The 1,3-beta-glucan synthases of Candida albicans and Aspergillus fumigatus were inhibited by arborcandins with IC50 ranging from 0.012 to 3 microg/ml. The apparent Ki value of arborcandin C for C. albicans and A. fumigatus were 0.12 microM and 0.016 microM, respectively. The inhibition against these two 1,3-beta-glucan synthases by arborcandin C was noncompetitive. These compounds exhibited potent fungicidal activity against Candida spp. with MIC ranging from 0.25 to 8 microg/ml. The growth of A. fumigatus was suppressed by arborcandins with concentrations ranging from 0.063 to 4 microg/ml.     

Lysis of methicillin-resistant Staphylococcus aureus by 2,4-diacetylphloroglucinol produced by Pseudomonas sp. AMSN isolated from a marine alga

Previously 2,4-diacetylphloroglucinol (DAPG) produced by Pseudomonas sp. AMSN isolated from a marine alga, had demonstrated a high level of anti-methicillin-resistant Staphylococcus aureus (MRSA) comparable with that of vancomycin. In this study, this substance had bacteriolytic activity against MRSA at 1 microg/ml as well as similar activity against Vibrio parahaemolyticus at 24 microg/ml that suggests a novel antibacterial mode of action by this substance. Heat and pH stability tests showed it to be stable at temperatures ranging from 35 to 70 degrees C and at pHs ranging from 2-7. It was not acutely toxic to mice at levels up to 100 mg/kg.     

TPU-0037-A,B, C and D,novel lydicamycin congeners with anti-MRSA activity from Streptomyces platensis TP-A0598

In screening for anti-MRSA antibiotics, novel lydicamycin congeners, TPU-0037-A, B, C and D, were isolated from a culture broth of an actinomycete strain. The producing strain, TP-A0598, was isolated from a seawater sample collected in Toyama Bay, Japan, and identified as Streptomyces platensis based on taxonomic characteristics. TPU-0037-A, B, C and D were purified by HP-20 resin, ODS column chromatographies and preparative HPLC, consecutively, and their structures were determined to be 30-demethyllydicamycin, 14,15-dehydro-8-deoxylydicamycin, 30-demethyl-8-deoxylydicamycin and 8-deoxylydicamycin, respectively, by NMR and MS analyses. The new congeners showed antibiotic activity against gram-positive bacteria including MRSA with the MIC of 1.56 to approximately 12.5 microg/ml.     

Antimicrobial activities of hydrophobic 2-arylbenzofurans and an isoflavone against vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus

Eight 2-arylbenzofurans and an isoflavone isolated from medicinal plants were tested for their antimicrobial activities against vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). Among these compounds, six hydrophobic 2-arylbenzofurans (log P = 4.4-8.7) exhibited considerable antibacterial activity against five VRE strains(VanA-, VanB-, and VanC-phenotypes) (MICs = 3.13-6.25 microg/mL). Five compounds also showed antibacterial activity against ten MRSA strains (MIC80 = 3.13 microg/mL).     

Clethramycin, a new inhibitor of pollen tube growth with antifungal activity from Streptomyces hygroscopicus TP-A0623. I. Screening, taxonomy, fermentation, isolation and biological properties

The cytoskeletal proteins, actin and myosin, play a central role in pollen tube growth. The pollen tube growth is inhibited by cytochalasin, which interferes with actin polymerization. In the screening of pollen tube growth inhibitors, clethramycin was found from the fermentation broth of an actinomycete strain TP-A0623. The producing strain was isolated from a root of Clethra barbinervis collected in Toyama, Japan and identified as Streptomyces hygroscopicus based on the taxonomic study. Clethramycin showed in vitro antifungal activity against yeast such as Candida albicans and C. glabrata with the MIC of 0.5 approximately 8 microg/ml, but weak activity against Gram-positive and negative bacteria (MIC > or = 64 microg/ml). Cytotoxicity of clethramycin was moderate and the IC50 was 57 microg/ml against HeLa cells and 120 microg/ml against WI-38 cells.     

Electron-microscopic study of the bactericidal effect of OPB-2045, a new disinfectant produced from biguanide group compounds, against methicillin-resistant Staphylococcus aureus

The bactericidal effect of OPB-2045, a new disinfectant produced from biguanide group compounds, against methicillin-resistant Staphylococcus aureus (MRSA), MRSA IID 1677, was investigated by transmission electron microscopy. OPB-2045 showed strong bactericidal activity against MRSA. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of OPB-2045 against the test strain were 0.78 and 1.56 microg mL(-1), respectively. The test bacteria were incubated in the presence of OPB-2045 at 1/2 MIC (0.39 microg mL(-1)), 1 MIC (0.78 microg mL(-1)), 2 MIC (1 MBC, 1.56 microg mL(-1)), 4 MIC (2 MBC, 3.13 microg mL(-1)) or 10 MIC (5 MBC, 7.8 microg mL(-1)) at 37 degrees C for 30 s, 3 min, 30 min or 6h. The morphology of the cells was examined by transmission electron microscopy. The cell damage observed after 30-min or 6-h incubation in the presence of OPB-2045 at 1/2 or 1 MIC was the same as that at 2, 4 or 10 MIC. The numbers of damaged MRSA cells increased according to the increase in concentration of added disinfectant, and the image of bacteriolysis was observed, too. After treatment at 1/2 or 1 MIC, a few leaking cells were recognized, but no destroyed cells were found. No morphological changes were observed after treatment at 1 or 2 MIC for 30 s, 3 min or 30 min. When the incubation time was extended to 6 h, morphological changes in the MRSA cells treated at 1 or 2 MIC were observed. When examining the relationship between the numbers of surviving bacteria and the MIC (MBC) values in soybean casein digest broth, no decrease in MRSA cell numbers was recognized in the untreated control or at 1/2 MIC, but a marked decrease in MRSA cell numbers was recognized as the OPB-2045 concentration was increased. The new disinfectant OPB-2045 would make a useful contribution to the medical field for the prevention of infections caused by pathogenic bacteria such as MRSA.     

Anti-MRSA cephalosporins Bristol-Myers Squibb

BMS is investigating a series of cephalosporins for potential use in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection [274213]. In vitro activity tests resulted in a minimum inhibitory concentration (MIC) of 1 to 8 microg/ml against MRSA 1274213]. A series of C(3) benzoyloxymethyl cephalosporins exhibited in vitro activity against MRSA and methicillin-susceptible Staphylococcus aureus (MSSA), with MIC values ranging from 0.007 to 2 microM, and improved in vivo stability in human plasma [258890].     

Structure-activity relationships of stemphones, potentiators of imipenem activity against methicillin-resistant Staphylococcus aureus

From a further purification study, four new stemphones D to G were isolated along with previously reported stemphones B and C from the culture broth of Aspergillus sp. FKI-2136. Twenty-one derivatives were semisynthetically prepared from stemphones C, E and G. Potentiation of imipenem activity against methicillin-resistant Staphylococcus aureus (MRSA) by all the stemphones including natural and semisynthetic ones was compared to study the structure-activity relationships. Derivatives with a free hydroxy or an O-acyl residue having a C2 to C5 carbon length at C-4 held the potentiating activity, but those with a longer acyl residue lost the activity. The presence of an oxo or a free hydroxy residue at C-10 is important for the potentiating activity because introduction of an alkyl or acyl residue at this position resulted in a loss of activity. Among them, stemphone E exhibited the most potent potentiation of imipenem activity against MRSA and the lowest cytotoxic activity against Jurkat cells.     

Kigamicins, novel antitumor antibiotics. I. Taxonomy, isolation, physico-chemical properties and biological activities

Novel antibiotics named kigamicin A, B, C, D, and E were discovered from the culture broth of Amycolatopsis sp. ML630-mF1 by their selective killing activity against PANC-1 cells only under a nutrient starved condition. Under a condition of nutrient starvation, kigamicins A, B, C, and D inhibited PANC-1 cell survival at 100 times lower concentration than in normal culture. Kigamicins showed antimicrobial activity against Gram-positive bacteria including methicillin resistant Staphylococcus aureus (MRSA). Kigamicin D inhibited the growth of various mouse tumor cell lines at IC50 of about 1 microg/ml.     

In vitro antimicrobial activity of telavancin against methicillin-resistant Staphylococcus aureus clinical isolates from Japan (2006)

In vitro antimicrobial activity of telavancin, a rapidly bactericidal lipoglycopeptide, was evaluated against 1500 strains of MRSA recently isolated in Japan. Telavancin had potent activity, with MIC values that ranged from 0.12 microg/ml to 0.5 microg/ml and a MIC90 value of 0.5 microg/ml. The MIC90s of vancomycin and linezolid were 1.0microg/ml and 2 microg/ml, respectively. No vancomycin intermediate resistant or vancomycin-resistant MRSAs were detected in this surveillance study.     

Susceptibilities of bacteria isolated from patients with lower respiratory infectious diseases to antibiotics (2002)

From October 2002 to September 2003, we collected the specimen from 476 patients with lower respiratory tract infections in 16 institutions in Japan, and investigated the susceptibilities of isolated bacteria to various antibacterial agents and patients' characteristics. Of 584 strains that were isolated from specimen (mainly from sputum) and assumed to be bacteria causing in inflammation, 578 strains were examined. The breakdown of the isolated bacteria were: Staphylococcus aureus 77, Streptococcus pneumoniae 103, Haemophilus influenzae 95, Pseudomonas aeruginosa (non-mucoid) 61, P. aeruginosa (mucoid) 23, Klebsiella pneumoniae 36, Moraxella subgenus Branhamella catarrhalis 29, etc. Of 77 S. aureus strains, those with 2 microg/ml or less of MIC of oxacillin (MPIPC) [methicillin-susceptible S. aureus: MSSA] was 34 strains (44.2%) and those with 4 microg/ml or more of MIC of oxacillin (methicillin-resistant S. aureus: MRSA) was 43 strains (55.8%). Against MSSA, imipenem (IPM) and minocycline (MINO) had the most potent antibacterial activity and inhibited the growth of all the strains at 0.25 microg/ml. Although clindamycin (CLDM) and aminoglycosides also had the potent activity, the resistant strains against those agents were detected. Cefotiam (CTM) inhibited the growth of all the strains at 1 microg/ml without the low sensitive strains. Against MRSA, vancomycin (VCM) showed the most potent activity and inhibited the growth of all the strains at 2 microg/ml. Arbekacin (ABK) also showed the relatively potent activity and inhibited the growth of all the strains at 4 microg/ml. Carbapenems showed the most potent activities against S. pneumoniae and inhibited the growth of all the strains at 0.25-0.5 microg/ml. Cefozopran (CZOP) also had a preferable activity (MIC90: 1 microg/ml) and inhibited the growth of all the strains at 2 microg/ml. In contrast, the resistant strains for cefaclor (CCL), erythromycin (EM), CLDM, and tetracycline (TC) were detected in 50.5%, 76.7%, 50.5%, and 80.6% of all the strains, respectively. Against H. influenzae, LVFX showed the most potent activity and inhibited the growth of 92 of all the strains (96.8%) at 0.063 microg/ml. Tobramycin (TOB) showed the most potent activity against P. aeruginosa (both mucoid and non-mucoid) and inhibited the growth of all the strains at 2 microg/ml. The antibacterial activity of CZOP was good and its MIC90 against mucoid and non-mucoid strains was 8 and 16 microg/ml, respectively. CZOP and cefpirome (CPR) were the most potent against K. pneumoniae with 0.125 microg/ml of MIC90. Also, all the agents generally showed potent activities against M. (B.) catarrhalis and the MIC90 of all drugs were 4 microg/ml or less. The approximately half the number (47.5%) of the patients with respiratory infection were aged 70 years or older. As for the incidence by the diseases, bacterial pneumonia and chronic bronchitis were the highest, being noted in 35.7 and 33.8% of all the patients, respectively. The bacteria frequently isolated from the patients with bacterial pneumonia were S. pneumoniae (22.6%). In contrast, S. aureus (16.6%) and P. aeruginosa (13.7%) were relatively frequently isolated from the patients with chronic bronchitis. Before the drug administration, the bacteria frequently isolated from all the patients were H. influenzae (24.5%) and S. pneumoniae (24.2%). In comparison of the isolated bacteria by pretreatment agents, P. aeruginosa was relatively frequently isolated from the patients pretreated with cephems or macrolides and H. influenzae was relatively frequently isolated from the patients pretreated with penicillins.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1999). I. Susceptibility distribution

The bacterial strains isolated from patients diagnosed as having urinary tract infections (UTIs) in 9 institutions in Japan were supplied between the period of August 1999 to July 2000. Then, the susceptibilities of them to many kinds of antimicrobial agents were investigated. The number of them were 499 strains. The breakdown of these strains was Gram-positive bacteria as 31.3% and Gram-negative bacteria as 68.7%. Susceptibilities of these bacteria to antimicrobial agents were as follows; vancomycin (VCM), ampicillin (ABPC) and imipenem (IPM) showed strong activities against Enterococcus faecalis. The increase of low-susceptible strains which was noticed in the former year showed a slight recovery in this year. VCM showed a strong activity against MRSA preventing growth of all strains with 1 microgram/ml. In addition, the activity of arbekacin (ABK) was also strong with the MIC90 of 2 micrograms/ml against MRSA. However, MSSA and MRSA showing low susceptibilities were detected in one strain each (MIC: 16 micrograms/ml and 32 micrograms/ml, respectively). Carbapenems showed high activities against Citrobacter freundii and Escherichia coli. Meropenem (MEPM) prevented growth of all strains within 0.125 microgram/ml. Quinolone resistant E. coli decreased in this year compared with those in the last year, that percentage was less than 5%. Almost all drugs showed strong activities against Klebsiella pneumoniae and Proteus mirabilis. MEPM and carumonam (CRMN) prevented growth of all strains within 0.125 microgram/ml. On the other hand, one strain of K. pneumoniae showing resistance to cefaclor (CCL) and one strain of P. mirabilis showing low susceptibility to most of cephems were detected. Against Pseudomonas aeruginosa, almost drugs were not so active. The MIC90s of carbapenems were 8 micrograms/ml and those of all other drugs were more than 16 micrograms/ml.     

FR209602 and related compounds, novel antifungal lipopeptides from coleophoma crateriformis no. 738. II. In vitro and in vivo antifungal activity

The biological activities of the novel echinocandin-like lipopeptides, FR209602, FR209603 and FR209604, were evaluated. These compounds showed antifungal activity against Candida albicans and Aspergillus fumigatus attributed to inhibition of 1,3-beta-glucan synthesis. The minimum effective concentrations of these compounds against C. albicans and A1. fumigatus ranged from 0.02 to 0.04 microg/ml by microbroth dilution assay, and the IC50 values on C. albicans 1,3-beta-glucan synthase were 0.49, 0.64 and 0.72 microg/ml, respectively. FR209602 and FR209603 showed good efficacy by subcutaneous injection against C. albicans in a murine systemic infection model, with ED50 values of 2.0 and 1.9 mg/kg, respectively.     

Mode of action of microbial anti-MRSA agents

Methicillin-resistant Staphylococcus aureus (MRSA) is known as a major nosocomial pathogen that has also developed resistance to many antibiotics. Moreover, MRSA resistance to a last-resort antibiotic, vancomycin, has been reported. Therefore, new anti-infectious agents to prevent and treat MRSA infection are needed. Based on this background, our group has focused on the discovery of new microbial agents active against MRSA infection. Viridicatumtoxin and spirohexaline, produced by Penicillium sp. FKI-3368, were isolated as inhibitors of undecaprenyl pyrophosphate (UPP) synthase of Staphylococcus aureus, which was involved in cell wall synthesis. Viridicatumtoxin and spirohexaline with a pentacyclic spiro skeleton inhibited UPP synthase activity with an IC(50) value of 4.0 and 9.0 μM, respectively. Actually, the growth of gram-positive bacteria including MRSA was strongly inhibited by the compounds. Our computational modeling experiments indicated that spirohexaline A was inserted into the substrate pocket of UPP synthase and interacted with Glu(88) via a carbamoyl group of the compound, with Ala(76), Met(54) and Asn(35) via three hydroxyl groups, and with certain hydrophobic amino acids via a spiro ring. Cyslabdan, produced by Streptomyces sp. K04-0144, was isolated as a potentiator of β-lactam imipenem activity against MRSA. The compound consisted of a labdan skeleton and an N-acetylcysteine. Cyslabdan potentiated imipenem activity by over 1000 fold, drastically reducing the MIC value of imipenem against MRSA from 16 to 0.03 μg/mL. The binding proteins of cyslabdan were investigated in the lysate of MRSA to identify FemA, which was involved in the formation of the pentaglycine interpeptide bridge in MRSA peptidoglycan.     

Sansanmycins B and C, new components of sansanmycins

Two new antibiotics, sansanmycins B and C, were isolated from Streptomyces sp. SS. Their structures were elucidated by extensive 1D and 2D NMR and MS spectral analyses. Sansanmycins B and C exhibited inhibitory activity against our test strain of Pseudomonas aeruginosa with MIC values of 8.0 and 16 microg/ml, respectively. Sansanmycin B also exhibited inhibitory activity against Mycobacterium tuberculosis H37Rv and multidrug-resistant Mycobacterium tuberculosis, with the MIC values ranging from 8.0 to 20 microg/ml.     

Psammaplin A, a natural bromotyrosine derivative from a sponge, possesses the antibacterial activity against methicillin-resistantStaphylococcus aureus and the DNA gyrase-inhibitory activity

Psammaplin A, a natural bromotyrosine derivative from an associated form of two sponges (Poecillastra sp. and Jaspis sp.) was found to possess the antimicrobial effect on the Gram-positive bacteria, especially on methicillin-resistant Staphylococcus aureus (MRSA). The minimal inhibitory concentration of psammaplin A against twenty one MRSAs ranged from 0.781 to 6.25 microg/ml, while that of ciprofloxacin was 0.391-3.125 microg/ml. Psammaplin A could not bind to penicillin binding protein, but inhibited the DNA synthesis and the DNA gyrase activity with the respective 50% (DNA synthesis) and 100% (DNA gyrase) inhibitory concentration 2.83 and 100 microg/ml. These results indicate that psammaplin A has a considerable antibacterial activity, although restricted to a somewhat narrow range of bacteria, probably by inhibiting DNA gyrase.     

Antiviral activity of seven iridoids, three saikosaponins and one phenylpropanoid glycoside extracted from Bupleurum rigidum and Scrophularia scorodonia

As part of our screening of antiviral agents from medicinal plants, 11 compounds from plant origin (Bupleurum rigidum and Scrophularia scorodonia), three saikosaponins, seven iridoids and one phenylpropanoid glycoside were tested in vitro against herpes simplex type I (HSV-1), vesicular stomatitis virus (VSV) and poliovirus type 1. Five of these compounds showed antiviral activity against VSV. The percentages of cellular viability at the non-toxic limit concentrations of the active compounds were: verbascoside 53.6 % at 500 microg/ml, 8-acetylharpagide 32.1 % at 500 microg/ml, harpagoside 43.3 % at 450 microg/ml, scorodioside 47.8 % at 500 microg/ml and buddlejasaponin IV 56.9 % at 25 microg/ml. Although none of the saikosaponins were active against HSV-1, the iridoid scorodioside showed moderate in vitro anti-HSV-1 activity (30.6 % at 500 microg/ml). However, none of the compounds tested in this survey had any effect against poliovirus.     

Synthesis,antibacterial and antifungal activities of electron-rich olefins derived benzimidazole compounds

New benzimidazole derivatives were synthesised by electron-rich olefines (7, 8 and 9) with appropriate reagents. The compounds synthesised were identified by 1H NMR, 13C NMR, FT-IR spectroscopic techniques and elemental analysis. All compounds studied in this work were screened for their in vitro antimicrobial activities against the standard strains: Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and the yeasts Candida albicans and Candida tropicalis. Eleven of the compounds inhibited the growth of gram-positive bacteria (E. faecalis and S. aureus) at MIC values between 50 and 400 microg/ml. None of the compounds exhibit antimicrobial activity against Gram-negative bacteria (E. coli and P. Aeruginosa) at the concentrations studied (6.25-800 microg/ml). Nine of the tested compounds showed an antifungal activity with a range of the MICs between 50 and 400 microg/ml.     

Novel human topoisomerase I inhibitors, topopyrones A, B, C and D. I. Producing strain, fermentation, isolation, physico-chemical properties and biological activity

In the course of a screening program for specific inhibitors of human topoisomerase I using a recombinant yeast, we have discovered four new active compounds. All four compounds were isolated from the culture broth of a fungus, Phoma sp. BAUA2861, and two of them were isolated from the culture broth of a fungus, Penicillium sp. BAUA4206. We designated these compounds as topopyrones A, B, C and D. Topopyrones A, B, C and D selectively inhibited recombinant yeast growth dependent on expression of human topoisomerase I with IC50 values of 1.22, 0.15, 4.88 and 19.63 ng/ml, respectively. The activity and selectivity of topopyrone B were comparable to those of camptothecin. The relaxation of supercoiled pBR322 DNA by human DNA topoisomerase I was inhibited by these compounds, however they did not inhibit human DNA topoisomerase II. Topopyrones A, B, C and D were cytotoxic to all tumor cell lines when tested in vitro. Topopyrone B has potent inhibitory activity against herpesvirus, especially varicella zoster virus (VZV). It inhibited VZV growth with EC50 value of 0.038 microg/ml, which is 24-fold stronger than that of acyclovir (0.9 microg/ml). Topopyrones A, B, and C were inhibitory to Gram-positive bacteria.