In vitro activity of anidulafungin and other agents against esophageal candidiasis-associated isolates from a phase 3 clinical trial.

The efficacy of anidulafungin, an echinocandin antifungal agent with potent anti-Candida activity, in treating esophageal candidiasis was tested in a double-blind study versus oral fluconazole. Isolates were identified and tested for susceptibility. Candida albicans represented >90% of baseline isolates. The MIC(90) of anidulafungin for all strains was 0.06 mg/liter.

Antimicrobial spectrum and potency of dalbavancin tested against clinical isolates from Europe and North America (2003): initial results from an international surveillance protocol.

Dalbavancin is a bactericidal dimethylaminopropyl amide glycopeptide derivative possessing an extended serum elimination half-life in humans that allows once-weekly dosing for the therapy of Gram-positive infections. Strains from this baseline surveillance protocol in North America (NA; USA and Canada) and Europe (EU, 14 countries) were sampled in 2003. A total of 7,765 Gram-positive isolates (3,695 from NA and 4,070 from EU) were tested by reference broth microdilution methods against dalbavancin and 10 comparator agents. Species were analyzed separately by resistance phenotypes such as methicillin- (oxacillin-) resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and penicillin-resistant Streptococcus pneumoniae. Dalbavancin and other glycopeptides were very active against staphylococci (n=4648) with dalbavancin being 16- to 32-fold more potent than vancomycin (MIC90, 0.06 versus 2 mg/L). MRSA rates were greater (31.6%) in NA than in EU (26.1%). Quinupristin/dalfopristin resistance (MIC, > or = 2 mg/L; 0.1-0.5%) was documented more often in EU compared to NA. Dalbavancin (MIC50, 0.03-0.06 mg/L) was active against enterococci, except VanA resistance phenotypes. VRE rates were lower in EU (8.3%) then in NA (35.9%) from this resistance-enhanced enterococcal collection. Streptococci (dalbavancin MIC90, 0.016-0.03 mg/L) were generally most susceptible to glycopeptides (100.0%), quinupristin/dalfopristin (98.6-100.0%) and linezolid (100.0%); but dalbavancin was 16-fold more active than comparators. All vancomycin-susceptible enterococci and > 90% of vanB VRE had dalbavancin MIC values at < or = 1 mg/L,but vanA VRE strains had dalbavancin MIC results ranging from 0.06 to > 8 mg/L (median MIC, > or = 8 mg/L). Dalbavancin MIC values were not adversely influenced by geographic region or resistance phenotype (except vanA VRE). Infrequently isolated Gram-positive organisms such as Bacillus spp. (MIC90, 0.12 mg/L), Corynebacterium spp. (MIC90, 0.12 mg/L), Listeria monocytogenes (MIC90, 0.25 mg/L) and Micrococcus spp. (MIC90, 0.03 mg/L) were very susceptible to dalbavancin. In conclusion, these 2003 baseline resistance surveillance findings confirm the potent dalbavancin activity compared to several comparator agents against important Gram-positive pathogens. This high volume international survey indicates potential therapeutic roles for dalbavancin against many troublesome resistant Gram-positive phenotypes.

Semisynthetic derivatives of purpuromycin as potential topical agents for vaginal infections.

Purpuromycin (1) is an antibiotic with a broad spectrum of antimicrobial activity, encompassing bacteria, fungi, and protozoa, particularly those involved in vaginal infections. With the aim of enhancing the solubility and reducing the serum binding, a chemical program of modifications was undertaken on the natural compound, and a new interesting series of derivatives at the naphthoquinone system was synthesized and evaluated as potential topical agents for vaginal infections. In particular three semisynthetic derivatives, 7'-amino (8a), 7'-methylamino (8b), 7'-ethylamino (8c), of 7'-demethoxypurpuromycin seemed to be the most promising. They were tested for in vitro activity against three of the most important vaginal pathogens and showed activity similar to that of purpuromycin against Candida isolates while they were significantly more active against Trichomonas vaginalis and Gardnerella vaginalis, which are cultured in media containing blood or serum. This is probably due to the fact that the activity of the derivatives is less antagonized by these supplements than that of purpuromycin.

Synthesis and antibacterial activity of a series of basic amides of teicoplanin and deglucoteicoplanin with polyamines.

Basic carboxamides of teicoplanin A2 (CTA) and its aglycon (TD) are prepared by condensation of the 63-carboxyl function of these antibiotics with linear or branched polyamines. The antimicrobial activities of some of the resulting compounds were better than those of the unmodified antibiotics. The presence of more than one basic group in the amidic chain enhanced the in vitro activity of some TD-amides against Gram-negative bacteria; two of these derivatives were also effective in vivo against Escherichia coli septicemia in the mouse. Among the CTA derivatives, the amide with spermine showed some unexpected in vitro activity against Gram-negatives. Both CTA- and TD-amides with polyamines are very soluble in water over a wide range of pH and are very hydrophilic.

Effect of protein on ramoplanin broth microdilution minimum inhibitory concentrations.

Ramoplanin is a glycolipodepsipeptide antibiotic active against Gram-positive bacteria. We observed that microdilution minimum inhibitory concentrations (MICs) were higher than those obtained in glass tubes or by agar dilution. Initial studies showed that these differences disappeared when 30% bovine serum was added to the broth. Further studies showed that addition of 0.01% bovine serum albumin (BSA) to the broth lowered the microdilution MICs for staphylococci, streptococci, and enterococci by four- to 32-fold. This phenomenon occurred in several commonly used growth media and in different types of commercially available microtiter trays. Precoating of the microtiter wells with a dilute solution of BSA (0.02%) had the same effect. It seems likely that ramoplanin adsorbs to plastic surfaces and is lost from solution, and that protein masks the sites of adsorption. Ramoplanin MICs may be reliably determined by broth microdilution if a small amount of protein is added to the diluent.

Determination of the number of tuf genes in Chlamydia trachomatis and Neisseria gonorrhoeae.

Restriction endonuclease fragments of DNA from Neisseria gonorrhoeae and Chlamydia trachomatis (mouse pneumonitis biovar) were hybridized to probes from the N-terminal and C-terminal portions of the Escherichia coli tufA gene. In common with other Gram-negative bacteria, the genome of N. gonorrhoeae was found to contain two homologous sequences (presumptive tuf genes). The C. trachomatis genome contained a single tuf sequence.

Octapeptide derivatives of teicoplanin antibiotics.

A series of octapeptide derivatives of teicoplanin-A2 component 2 (CTA/2), its aglycone (TD), and the L-lysyl derivatives of an amide of CTA/2 and TD, were prepared by condensation of the terminal amino group with N-hydroxysuccinimidyl esters of tert-butyloxycarbonyl (BOC) L- and D-amino acids, followed by acidic (TFA) removal of the BOC protecting function. The antimicrobial properties of these compounds were compared with those of the corresponding unmodified antibiotics and their N15-acetyl derivatives. The most active derivatives were the octapeptides with N-terminal glycine or lysine whose in vitro activity was comparable to that of the parent teicoplanins. The glycinyl and lysyl derivatives of CTA/2 showed better activity than CTA/2 against clinical isolates of Staphylococcus epidermidis and S. haemolyticus for which teicoplanin MICs were relatively high. No significant difference in their antibacterial activity was observed between octapeptides containing L- or D-lysine.

Amides of de-acetylglucosaminyl-deoxy teicoplanin active against highly glycopeptide-resistant enterococci. Synthesis and antibacterial activity.

Removal, by selective reduction, of the acetylglucosamine from teicoplanin A2-2 (CTA/2) produced the 34-de(acetylglucosaminyl)-34-deoxy pseudoaglycone (II). This compound was more active in vitro than CTA/2 against coagulase-negative staphylococci (CNS). Amide derivatives obtained by condensation of the carboxyl group of II with primary amines were particularly active against Streptococcus pyogenes and had some in vitro activity against VanA enterococci highly resistant to both teicoplanin and vancomycin. Among them, a carboxamide (VII) with a branched tetramine also had better activity than the corresponding amide of teicoplanin against CNS. In contrast, the dimethylamide (VIII) of II had little activity against VanA enterococci. While the overall structure of the heptapeptide backbone of the secondary carboxamides of II is the same as in CTA/2 and its amide derivatives, in deoxy pseudoaglycone II and its tertiary amide VIII the 51,52-peptide bond undergoes a conformational change from the original cisoid to the transoid orientation. This difference between the secondary amides of II and dimethylamide VIII is reflected in their different antibacterial spectrum. The direct synthesis of the amides of deoxy pseudoaglycone II from parent CTA/2-amides by reaction with sodium borohydride is also described.

Antimicrobial activities of chemically modified thiazolyl peptide antibiotic MDL 62,879 (GE2270A).

MDL 62,879 (GE2270A) 1 is a new inhibitor of elongation factor-Tu (EF-Tu) and belongs to the class of thiazolyl peptide antibiotics. Controlled acid hydrolysis of 1 followed by treatment with base resulted in the lost of the two terminal amino acids and in the formation of water-soluble MDL 62,935 2. Although less active in vitro than its parent compound, 2 was able to inhibit by 50% an Escherichia coli cell-free protein synthesis system at roughly the same concentration of 1. MDL 62,935 2 was subjected to further modification at the beta-phenylserine residue. Derivatives obtained from 2 were less active in both antimicrobial (MIC) and enzymatic (IC50) assays. This suggests that beta-phenylserine plays an important role for the inhibition of EF-Tu by 1 and 2.

Antibiotics A21459 A and B, new inhibitors of bacterial protein synthesis. I. Taxonomy, isolation and characterization.

Novel cyclic peptide antibiotics A21459 A and B are produced by a member of the genus Actinoplanes sp. These antibiotics inhibit bacterial protein synthesis and have selective antimicrobial activity against clostridia, mycoplasma and some Gram-negative bacteria.

Antibiotic SB22484: a novel complex of the aurodox group. I. Taxonomy of the producing organism, isolation of the antibiotics and chemical and biological characterization.

Antibiotic SB22484 is a novel member of the aurodox type antibiotic group produced in submerged-fermentation cultures of Streptomyces sp. NRRL 15496. The antibiotic complex is composed of two pairs of isomers with MW's of 752 and 766. The individual isomers, which were separated by preparative HPLC, equilibrate to a mixture of the isomer pair when left in aqueous solution. In vitro, SB22484 antibiotics strongly inhibited neisseriae and were also active against Streptococci, Ureaplasma urealyticum and Haemophilus influenzae.

Structure and biological activity of lipiarmycin B.

Actinoplanes deccanensis ATCC 21983, the producer of antibiotics lipiarmycin A3 and A4, furnished also a related antibiotic designated lipiarmycin B, active against Gram-positive bacteria, including anaerobes, and against Neisseria. The structures of the two major components, B3 and B4, were elucidated from their physico-chemical properties, 1H and 13C NMR spectra and fast atom bombardment mass spectra data in comparison with lipiarmycins A3 and A4.

Antibiotic GE2270 a: a novel inhibitor of bacterial protein synthesis. I. Isolation and characterization.

A novel antibiotic, GE2270 A, was isolated from the fermentation broth of a strain of Planobispora rosea. The product was found to inhibit bacterial protein synthesis. Structural characteristics showed similarities between GE2270 A and thiazolyl peptides such as micrococcin which is known to inhibit protein synthesis by acting directly on the ribosome. Despite this similarity GE2270 A showed functional analogy to kirromycin-like antibiotics and pulvomycin, as its molecular target was found to be elongation factor Tu (EF-Tu). GE2270 A is active against Gram-positive microorganism and anaerobes and differs from the other EF-Tu inhibitors in its spectrum of antimicrobial activity.

Antibiotic GE37468 A: a new inhibitor of bacterial protein synthesis. I. Isolation and characterization.

GE37468 A is a new thiazolyl peptide antibiotic obtained by fermentation of Streptomyces sp. strain ATCC 55365. It inhibits bacterial protein synthesis by acting on elongation factor Tu and is structurally and functionally related to the GE2270 class of EF-Tu inhibitors. It is active in vitro against Gram-positive bacteria and Bacteroides fragilis, and protects mice against Staphylococcus aureus infection.

New semisynthetic glycopeptides MDL 63,246 and MDL 63,042, and other amide derivatives of antibiotic A-40,926 active against highly glycopeptide-resistant VanA enterococci.

A series of amide derivatives of natural glycopeptide A-40,926 (A), its 6B-methyl ester (MA) and 6B-decarboxy-6B-hydroxymethyl derivative (RA) were prepared with the aim of obtaining activity against glycopeptide-resistant enterococci. These compounds are structurally related to a class of amides of 34-de(acetylglucosaminyl)-34-deoxy teicoplanin which showed interesting activity against strains of Enterococcus faecalis and E. faecium highly resistant to both vancomycin and teicoplanin. Among them, RA-amides MDL 63,246 and MDL 63,042 were the most active derivatives against several Gram-positive bacteria, including VanB and VanC enterococci, and were moderately active (MIC range 0.5 approximately 64 micrograms/ml) against strains of Enterococcus for which vancomycin and teicoplanin MICs were > or = 128 micrograms/ml. The chemical rationale and the synthesis of these new series of glycopeptide derivatives are described. Preliminary in vitro data are reported and structure-activity relationships are discussed.

N63-carboxamides of N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin and deglucoteicoplanin.

The synthesis and biological properties of a series of N63-carboxamides of 15-N-alkylated derivatives of teicoplanin A2 (CTA) and its aglycone (TD) are described. Among the compounds, those carrying hydrophilic groups or ionizable amino functions on the N15-alkyl chain are more soluble in water than parent N15-methylated or unmodified amides. Selected compounds were more active in vitro than CTA or TD, and a few of them were also slightly more efficacious in vivo than the parent antibiotics in streptococcal septicemia in the mouse. Their degree of activity varied with the structure and length of the N15-alkyl chains.

Carboxamides and hydrazide of glycopeptide antibiotic eremomycin. Synthesis and antibacterial activity.

Carboxamides and hydrazide of glycopeptide antibiotic eremomycin were obtained by a direct reaction of the carboxy group of eremomycin with an appropriate amine or hydrazine using diphenyl phosphorazidate as a condencing agent. Eremomycin hydrazide was also obtained by hydrazinolysis of the eremomycin methyl ester. Use of dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide for amidation led to the corresponding eremomycin ureides. The ESI-MS data indicate that eremomycin and its amides exist as dimers. The carboxamide, methylamide and benzylamide of eremomycin were as active against Gram-positive bacteria as the parent antibiotic, and the methylamide, benzylamide and hydrazide were almost an order of magnitude more active than eremomycin against Staphylococcus epidermidis clinical isolates in vitro. Amide of eremomycin as well as ureides were devoid of histamine liberating properties, which demonstrates that protection of the carboxyl group leads to a decrease in the allergenic properties.

Synthesis and antibacterial activity of derivatives of the glycopeptide antibiotic A-40926 and its aglycone.

Starting from the antibiotic A-40926 and the aglycone of A-40926 a series of compounds were prepared by modifying the free functionalities. Their antimicrobial activity was determined, particularly against Neisseria gonorrhoeae, against which A-40926, unlike other natural glycopeptides, is active. Improved in vivo activity was displayed by the monomethyl ester of A-40926 esterified at the carboxyl group of the N-acylamino-glucuronyl moiety.

A42867, a novel glycopeptide antibiotic.

A42867 is a new glycopeptide antibiotic of the ristocetin-vancomycin class active against aerobic and anaerobic Gram-positive bacteria. A42867 is produced by a strain of Nocardia nov. sp. ATCC 53492. A42867 was isolated during a screening program aimed at the discovery of new members of this glycopeptide class of antibiotics, by affinity chromatography based on an acyl-D-alanyl-D-alanine probe. The structure of A42867 was elucidated by fast atom bombardment MS, high field 2D 1H NMR spectroscopy, and HPLC analysis of the hydrolyzed carbohydrates. A42867 differs from vancomycin in the sugar portion and in the presence of only one chlorine atom in the peptide core. Its biological activity on Gram-positive aerobic and anaerobic bacteria is similar to that of other antibiotics of this group.

A40926 aglycone and pseudoaglycones: preparation and biological activity.

A40926 antibiotics are new glycopeptides which are much more active than other members of this class against Neisseria gonorrhoeae. Their activity against Gram-positive bacteria, including coagulase-negative Staphylococci, is similar to that of other glycopeptides. An A40926 preparation containing factors A and B ("A40926 A + B complex") was hydrolyzed to the aglycone and to the mannosyl and N-acylaminoglucuronyl aglycones. The mannosyl aglycone and the aglycone were less active than A40926 A + B complex against Streptococci and Gram-positive anaerobes and lost the anti-gonorrheal activity. In contrast, the N-acylaminoglucuronyl aglycones were as active as the parent complex against these Gram-positive bacteria and were moderately active against N. gonorrhoeae. The aglycone and, even more so, the N-acylaminoglucuronyl aglycones, had better activity than the parent complex against coagulase-negative Staphylococci. In experimental septicemia in the mouse, A40926 A + B complex and its derivatives had activity proportional to their MIC for the test organism.