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PubMed2003

Comparison of media for enumeration of Clostridium perfringens from foods.

Many media have been developed to enumerate Clostridium perfringens from foods. In this study, six media [iron sulfite (IS) agar, tryptose sulfite cycloserine (TSC) agar, Shahidi Ferguson perfringens (SFP) agar, sulfite cycloserine azide (SCA), differential clostridial agar (DCA), and oleandomycin polymyxin sulfadiazine perfringens (OPSP) agar] were compared in a prestudy, of which four (IS, TSC, SCA, and DCA) were selected for an international collaborative trial. Recovery of 15 pure strains was tested in the prestudy and recovery of one strain from foodstuffs was tested in the collaborative trial. Results from the prestudy did reveal statistical difference of the media but recoveries on all media were within the microbiological limits (+/-30%) of IS, which was set as a reference medium. Recoveries on the media tested in the collaborative trial were statistically different as well, but these differences were of no microbiological-analytical relevance. Food matrices did not affect the recovery of C. perfringens in general. DCA and SCA, in particular, are labor-intensive to prepare and DCA frequently failed to produce black colonies; gray colonies were quite common. Since IS medium is nonselective, it was concluded that TSC was the most favorable medium for the enumeration of C. perfringens from foods.

Animals↗
PubMed2004

The role of histidine residues conserved in the putative ATP-binding region of macrolide 2'-phosphotransferase II.

Macrolide 2'-phosphotransferase (MPH(2')) catalyzes the transfer of the gamma-phosphate of ATP to the 2'-hydroxyl group of macrolide antibiotics. In this study, H198 and H205, conserved in the ATP-binding region motif 1 in the putative amino acid sequence of MPH(2')II, were replaced by Ala to investigate their role. H205 was also subsequently replaced by Asn. H198A and H205N mutant enzymes retained more than 50% of the specific activity of the original enzyme to substrate oleandomycin. On the other hand, the specific activity of the H205A mutant enzyme was reduced to less than 1% of that of the wild enzyme. The results suggested that H205 is crucial for maintaining the catalytic activity of MPH(2')II, and Asn can substitute for His at this position.

Adenosine Triphosphate↗
PubMed2000

Genetic architecture of the polyketide synthases for methymycin and pikromycin series macrolides.

The methymycin and pikromycin series of antibiotics are structurally related macrolides produced by several Streptomyces species, including Streptomyces venezuelae ATCC 15439, which produces both 12-membered ring macrolides methymycin, neomethymycin, and 14-membered ring macrolides pikromycin and narbomycin. Cloning and sequencing of the biosynthetic gene clusters for these macrolides from three selected Streptomyces strains revealed a common genetic architecture of their polyketide synthases (PKSs). Unlike PKS clusters of other 14-membered ring macrolides such as erythromycin and oleandomycin, each of the pikromycin series producers harbors a six module PKS cluster, in which modules 5 and 6 are encoded on two separate proteins instead of one bimodular protein, as well as a thioesterase II gene immediately downstream of the main PKS gene. The results shed new light on the evolution of modular PKSs and provide further evidence on the regulation of methymycin and pikromycin production in S. venezuelae ATCC 15439.

Amino Acid Sequence↗
PubMed1997

Determination of erythromycin concentrations in rat plasma and liver by high-performance liquid chromatography with amperometric detection.

A simple method for the quantitative determination of erythromycin (EM) concentrations in rat plasma and liver by high-performance liquid chromatography with amperometric detection was developed. EM was extracted from 200 microl of plasma or liver homogenate sample under sodium hydroxide alkaline conditions with tert.-butyl methyl ether. Oleandomycin was used as an internal standard. The recovery rate of EM was up to 100%. The detector cell potential for the oxidation of EM was +1100 mV. The calibration curves were linear over the concentration ranges 0.1-20.0 microg/ml for plasma and 0.5-100.0 microg/g for liver. The method was applied to the determination of the plasma and liver concentrations of EM in rats after intravenous administration (50 mg/kg dose). The method presented here has proved to be of great use for the investigation of the pharmacokinetic characteristics of EM in small animals such as rats.

Animals↗
PubMed2000

Dose uniformity and redispersibility of pharmaceutical suspensions 2: assessment of three commercial erythromycin ethyl succinate oral liquids.

The content of active ingredient of single doses of a suspension depends to a large extent upon the redispersibility of the product. Mathematical and technical aspects of a procedure to test this property have been discussed in a preceding article. Here, the method is applied to three commercial erythromycin ethylsuccinate suspensions obtained from community pharmacies in Germany. Three specimens of each product were tested in parallel. For approximately two weeks, samples were taken t.i.d. at 9 am, 1 pm and 5 pm after shaking the bottles on a prototype testing apparatus with an intensity of 134m(2)/s(3) per cycle corresponding to the 25th percentile of a group of 79 subjects, whose shaking habits had been assessed previously. In order to minimize volumetric errors, 2.5ml samples were drawn using a syringe. They were assayed by HPLC with electrochemical detection using oleandomycin as an internal standard. While one of the products performed satisfactorily and one showed moderate shortcomings, the dose uniformity of two specimens of the third product was clearly deficient. The problem seems to be associated with poor wetting behaviour of the solids.

Administration, Oral↗
PubMed2002

Engineering deoxysugar biosynthetic pathways from antibiotic-producing microorganisms. A tool to produce novel glycosylated bioactive compounds.

A plasmid (pLN2) was generated in which genes involved in the biosynthesis of L-oleandrose in the oleandomycin producer Streptomyces antibioticus ATCC11891 were cloned. pLN2 was used to direct the biosynthesis of different deoxysugars by exchanging and/or adding genes from other antibiotic biosynthetic clusters. Transfer of the synthesized deoxysugars to the tetracenomycin C aglycon, 8-demethyl-tetracenomycin C, through the use of the "sugar flexible" glycosyltransferase ElmGT, validated the system. Several pLN2 derivatives were constructed by replacement of the oleU 4-ketoreductase gene by different 4-ketoreductase genes. Some of them, such as EryBIV and UrdR, reduced the keto group of the 4-keto intermediates, generating L-olivosyl and D-olivosyl derivatives, respectively. The system was also used to generate an L-rhamnosyl derivative (through a two-gene deletion) and an L-rhodinosyl derivative (through a combination of a gene replacement and a gene addition).

Anti-Bacterial Agents↗
PubMed1980

Comparison of media and methods for counting Clostridium perfringens in poultry meat and further-processed products.

A Most Probable Number (MPN) method involving Differential Reinforced Clostridial Medium followed by streaking on Willis & Hobbs medium was compared with direct plating of samples on Tryptose-Sulphite-Cycloserine agar without egg yolk, and two forms of Oleandomycin-Polymyxin-Sulphadiazine-Perfringens agar, one being prepared from a commercial, dehydrated product. With skin samples taken from chicken carcasses at different stages of processing, the three direct plating media gave similar counts of Cl. perfringens whereas results obtained with the MPN method were consistently lower. Although counts of Cl. perfringens from various further processed products were usually less than 10/g, the three plating media showed similar specificity for this organism. All media supported good growth of reference strains of Clostridium perfringens but it was found that physiologically similar species, including Cl. absonum, Cl. paraperfringens and Cl. perenne also grew uninhibited in these media and produced colonies identical with those of Cl. perfringens, thus indicating the need for confirmatory tests for Cl. perfringens when examining natural samples.

Animals↗
PubMed2002

Asymmetric crotylation reactions in synthesis of polypropionate-derived macrolides: application to total synthesis of oleandolide.

Complete details of a convergent asymmetric synthesis of oleandolide (1), the aglycon of the macrolide antibiotic oleandomycin, is described. The synthesis has been achieved through the assembly and coupling of the left- and right-hand subunits 12 and 38, respectively. These subunits were prepared from chiral silane-based asymmetric crotylation reactions to control the stereochemical relationships. The left- and right-hand subunits (C1-C7 and C8-C14) were brought together through a Pd(0)-catalyzed sp3-sp2 cross-coupling reaction between the zinc intermediate 40 and vinyl triflate 38 to give 27. This product was converted to seco acid 42a and cyclized to lactone 35 under Yamaguchi conditions. This material was then epoxidized with m-chloroperbenzoic acid (m-CPBA) to install the correct C8 epoxide as a single diastereomer, which after a short deprotection sequence completed the synthesis of oleandolide.

Anti-Bacterial Agents↗
PubMed2006

Determination of five macrolide antibiotic residues in raw milk using liquid chromatography-electrospray ionization tandem mass spectrometry.

A confirmatory method using liquid chromatography-electrospray ionization tandem mass spectrometry for determination of five macrolide antibiotics including spiramycin, tilmicosin, oleandomycin, erythromycin, and tylosin in raw milk is presented. Macrolides were extracted from raw milk by acetonitrile, and sample extracts were further cleaned up using solid-phase extraction cartridges. Data acquisition was achieved using multiple reaction monitoring, that is, two transitions, to provide a high degree of sensitivity and specificity. Matrix-matched standard calibration curves with the use of roxithromycin as an internal standard were utilized to achieve the best accuracy of the method. Both a conventional validation procedure and a designed experiment were applied to study the accuracy and precision of the method. The measurement uncertainty arising from accuracy and precision was estimated. The method accuracy, expressed as a percentage of overall recovery, was approximately 100%, and its intermediate precision was <10%. LC-ESI/MS/MS method detection limits (S/N > or = 3:1) of five macrolides were <0.3 microg/kg.

Animals↗
PubMed1997

Metabolic interactions of selected antimalarial and non-antimalarial drugs with the major pathway (3-hydroxylation) of quinine in human liver microsomes.

AIMS: Nine antimalarial (plus two metabolites of proguanil) and twelve non-antimalarial drugs were tested for their possible interaction with CYP3A4-catalysed 3-hydroxylation of quinine by human liver microsomes in vitro. METHODS: 3-Hydroxyquinine was assayed in the incubation mixture by an h.p.l.c. method using fluorometric detection. The respective IC50 values were estimated for the twenty-one drugs and two metabolites of proguanil tested herein. RESULTS: Thirteen drugs exhibited an inhibitory effect on the 3-hydroxylation of quinine. According to the respective mean IC50 values, the inhibitory rank order of the drugs was: ketoconazole > troleandomycin (TAO, with preincubation) > doxycycline > omeprazole > primaquine > tetracycline = TAO (without preincubation) > nifedipine > erythromycin > verapamil > cimetidine > diltiazem > oleandomycin > hydralazine. Other drugs or metabolites showed little or no inhibition of quinine metabolism (mean IC50 > 200 or 500 microM). Among the antimalarial drugs, doxycycline showed relatively potent inhibition of quinine 3-hydroxylation with a mean IC50 value of 17 microM, followed by primaquine and tetracycline, with mean IC50 values of 20 and 29 microM, respectively. CONCLUSIONS: When the plasma/serum concentrations possibly attained after their usual therapeutic doses were taken into account, tetracycline, doxycycline, omeprazole, ketoconazole, nifedipine, TAO and erythromycin are likely to be inhibitors of quinine metabolism in patients when the drugs are co-administrated with quinine.

Anti-Infective Agents↗
PubMed1997

Erythromycin resistance peptides selected from random peptide libraries.

Translation of a 5-codon mini-gene encoded in Escherichia coli 23 S rRNA was previously shown to render cells resistant to erythromycin (Tenson, T., DeBlasio, A., and Mankin, A. S. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 5641-5646). Erythromycin resistance was mediated by a specific interaction of the 23 S rRNA-encoded pentapeptide with the ribosome. In the present study, peptides conferring erythromycin resistance were selected from in vivo expressed random peptide libraries to study structural features important for peptide activity. Screening of a 21-codon mini-gene library (the general structure ATG (NNN)20 TAA) demonstrated that only short peptides (3-6 amino acids long) conferred erythromycin resistance. Sequence comparison of erythromycin resistance peptides isolated from the 5-codon library (ATG (NNN)4 TAA) revealed a strong preference for leucine or isoleucine as a third amino acid and a hydrophobic amino acid at the C terminus of the peptide. When tested against other antibiotics, erythromycin resistance peptides rendered cells resistant to other macrolides, oleandomycin and spiramycin, but not to chloramphenicol or clindamycin. Defining the consensus amino acid sequence of erythromycin resistance peptides provided insights into a possible mode of peptide action and the nature of the peptide binding site on the ribosome.

Chromosome Mapping↗
PubMed1990

Immunosuppression by gramicidin S of experimental autoimmune uveoretinitis, pinealitis and autoimmune encephalomyelitis.

Using an in vitro lymphocyte proliferation assay we screened several cyclic peptide antibiotics (bacitracin, oleandomycin, capreomycin, colistin, virginiamycin, and gramicidin S) for their immunosuppressive activity. Gramicidin S (GrS) was found to inhibit [3H]-thymidine incorporation into concanavalin A-stimulated and E coli lipopolysaccharide-stimulated lymphocytes. In vivo studies, experimental autoimmune uveoretinitis (EAU) and pinealitis were induced in female Lewis rats by immunization with bovine S-antigen and experimental autoimmune encephalomyelitis (EAE) were induced by immunization of rats with rat brain homogenates. GrS suppressed the onset of these inflammatory diseases at nontoxic concentrations. Evidence was obtained that GrS inhibits [3H]-thymidine incorporation into lymphocytes by preventing transport of the compound across the membrane. Since GrS binds to various cell membranes, GrS would suppress the proliferation of not only lymphocytes but also of other immune cells by modifying cell membrane properties. The present study indicates that a search for compounds which cause proper cell membrane modification should be a worthwhile strategy for development of immunosuppressive drugs.

Amino Acid Sequence↗
PubMed1985

Determination of the activity on Legionella of eight macrolides and related agents by comparative testing on three media.

It has proved difficult to develop a standard method for the determination of minimum inhibitory concentrations (MICs) of antibiotics against the Legionellaceae. A major obstacle has been the inactivation of certain antibiotics by components of Charcoal Yeast Extract agar, especially charcoal. To determine the MICs of eight macrolides and related agents (erythromycin, spiramycin, oleandomycin, josamycin, midecamycin, lincomycin, clindamycin and pristinamycin) for 36 strains of Legionella, we used two charcoal-free media: Buffered Yeast Extract agar and Buffered Antibiotic Medium no. 1 (BAM1), the latter having been developed in our own laboratory. The inhibitory effect of charcoal was most marked on josamycin and pristinamycin. This effect was absent on the charcoal-free media, which both, however, inhibited spiramycin. BAM1 agar seemed the better of the two charcoal-free media as it gave more consistent growth. The most active agents were josamycin (0.06-0.25 mg/l), pristinamycin (0.06-0.5 mg/l) and erythromycin (0.12-0.5 mg/l). Midecamycin (0.12-1 mg/l) and spiramycin (1-5 mg/l) also had useful activity.

Anti-Bacterial Agents↗
PubMed1985

The in-vitro activity of pristinamycin against Haemophilus influenzae and Neisseria meningitidis.

The in-vitro activity of erythromycin, oleandomycin, spiramycin, josamycin and pristinamycin was tested by a plate-dilution method against strains of Haemophilus influenzae and Neisseria meningitidis. Pristinamycin was the most active product tested with minimal inhibitory concentrations (MIC) ranging between 0.5 and 4 mg/l for H. influenzae (modal value 1 mg/l) and between 0.03 and 0.12 mg/l for N. meningitidis (modal value 0.06 mg/l).

Anti-Bacterial Agents↗
PubMed1987

Origin and evolution of genes specifying resistance to macrolide, lincosamide and streptogramin antibiotics: data and hypotheses.

Resistance to macrolide, lincosamide and streptogramin antibiotics is due to alteration of the target site or detoxification of the antibiotic. Postranscriptional methylation of 23S ribosomal rRNA confers resistance to macrolide (M), lincosamide (L) and streptogramin (S) B-type antibiotics, the so-called MLSB phenotype. Several classes of rRNA methylases conferring resistance to MLSB antibiotics have been characterized in Gram-positive cocci, in Bacillus spp, and in strains of actinomycetes producing erythromycin. The enzymes catalyze N6-dimethylation of an adenine residue situated in a highly conserved region of prokaryotic 23S rRNA. In this review, we compare the amino acid sequences of the rRNA methylases and analyze the codon usage in the corresponding erm (erythromycin resistance methylase) genes. The homology detected at the protein level is consistent with the notion that an ancestor of the erm genes was implicated in erythromycin resistance in a producing strain. However, the rRNA methylases of producers and non-producers present substantial sequence diversity. In Gram-positive bacteria the preferential codon usage in the erm genes reflects the guanosine plus cytosine content of the chromosome of the host. These observations suggest that the presence of erm genes in these micro-organisms is ancient. By contrast, it would appear that enterobacteria have acquired only recently an rRNA methylase gene of the ermB class from a Gram-positive coccus since the genes isolated in Escherichia coli and in Gram-positive cocci are highly homologous (homology greater than 98%) and present a codon usage typical of the latter micro-organisms. As opposed to the MLSB phenotype which results from a single biochemical mechanism, inactivation of structurally related antibiotics of the MLS group involves synthesis of various other enzymes. In enterobacteria, resistance to erythromycin and oleandomycin is due to production of erythromycin esterases which hydrolyze the lactone ring of the 14-membered macrolides. We recently reported the nucleotide sequence of ereA and ereB (erythromycin resistance esterase) genes which encode erythromycin esterases type I and II, respectively. The amino acid sequences of the two isozymes do not exhibit statistically significant homology. Analysis of codon usage in both genes suggests that esterase type I is indigenous to E. coli, whereas the type II enzyme was acquired by E. coli from a phylogenetically remote micro-organism. Inactivation of lincosamides, first reported in staphylococci and lactobacilli of animal origin, was also recently detected in Gram-positive cocci isolated from humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1988

Mechanism of action of spiramycin and other macrolides.

Macrolide antibiotics constitute a group of 12 to 16-membered lactone rings substituted with one or more sugar residues, some of which may be amino sugars. They inhibit bacterial protein synthesis both in vivo and in vitro with varying potencies. Macrolides are generally bacteriostatic, although some of these drugs may be bactericidal at very high concentrations. The mechanism of action of macrolides has been a matter of controversy for some time. Spiramycin, a 16-membered macrolide, inhibits translocation by binding to bacterial 50S ribosomal subunits with an apparent 1:1 stoichiometry. This antibiotic is a potent inhibitor of the binding to the ribosome of both donor and acceptor substrates. Spiramycin induces rapid breakdown of polyribosomes, an effect which has formerly been interpreted as occurring by normal ribosomal run-off followed by an antibiotic-induced block at or shortly after initiation of a new peptide. However, there is now convincing evidence that spiramycin, and probably all macrolides, act primarily by stimulating the dissociation of peptidyl-tRNA from ribosomes during translocation. Although the ribosomes of both Gram-positive and Gram-negative organisms are susceptible to macrolides, these antibiotics are mainly used against Gram-positive bacteria since they are unable to enter the porins of Gram-negative bacteria. Resistance to macrolides in clinical isolates is most frequently due to post-transcriptional methylation of an adenine residue of 23S ribosomal RNA, which leads to co-resistance to macrolides, lincosamides and streptogramins type B (the so-called MLSB phenotype). Other mechanisms of resistance involving cell impermeability or drug inactivation have been detected in Staphylococcus spp. and Escherichia coli. These strains are resistant to 14-membered macrolides (erythromycin and oleandomycin) but remain susceptible to spiramycin.

Anti-Bacterial Agents↗
PubMed1989

Macrolide-lincosamide-streptogramin B (MLS) resistance in cutaneous propionibacteria: definition of phenotypes.

Erythromycin-resistant propionibacteria isolated from the skin of antibiotic-treated acne patients were found to express four different patterns of resistance to a set of eight MLS antibiotics. The majority of isolates (48/89 strains) were constitutively resistant to 14- and 16-membered ring macrolide, lincosamide and streptogramin B-type antibiotics. MICs of josamycin (0.5-16 mg/l) and spiramycin (0.5-128 mg/l) were lower than those of erythromycin, oleandomycin and tylosin (64 to less than 512 mg/l). Two strains of Propionibacterium granulosum exhibited inducible MLS resistance. Both 14- and 16-membered ring macrolides and virginiamycin S induced clindamycin resistance in these strains. Fifteen isolates demonstrated a similar phenotype to the inducible strains but were non-inducible by erythromycin. A fourth group of strains demonstrated high level resistance to all five macrolides tested (MIC greater than or equal to 128 mg/l) but were sensitive to virginiamycin S. The phenotype displayed by these strains is not compatible with the expression of methylase genes as currently known, nor with the action of an erythromycin esterase which hydrolyses only 14-membered ring macrolides. The resistance patterns of 12 isolates could not be classified into any of the above phenotypic classes. Therefore, the majority of erythromycin resistant propionibacteria express MLS resistance which is phenotypically similar to that coded for by several well characterized RNA methylase (erm) genes.

Anti-Bacterial Agents↗
PubMed1993

Chemistry and mode of action of macrolides.

After the discovery of erythromycin and other natural compounds, including oleandomycin, spiramycin, josamycin and midecamycin, much research has been devoted to synthesizing derivatives or analogues with improved chemical, biological and pharmacokinetic properties. These new macrolides are semisynthetic molecules that differ from the original compounds in their substitution pattern of the lactone ring system. The chemical structure of macrolides is characterized by a large lactone ring containing from 12 to 16 atoms to which are attached, via glycosidic bonds, one or more sugars. The lactone ring is substituted by hydroxyl or alkyl groups, one ketone at C7 in 12-membered macrolides and at C9 in 14-membered macrolides, and one aldehyde group in 16-membered macrolides. The only compound with a 15-membered ring contains a tertiary amino group. Although the 12-membered macrolides have never become important in clinical practice, in recent years numerous new 14-membered macrolide derivatives of erythromycin A have shown improved pharmacokinetics due to chemical modifications of a hydroxyl group at C6, a proton at C8, or a ketone at C9. Derivatives, such as dirithromycin, roxithromycin, clarithromycin and flurithromycin, have all been synthesized with the aim of inhibiting their decomposition under acidic conditions to inactive anhydrohemiketal derivatives. A new 15-membered macrolide, azithromycin, with a methylated nitrogen inserted into the lactone ring shows good activity against Gram-negative bacteria. The efforts expended in chemical and biochemical modifications of 16-membered macrolides have been less successful, with only a few new molecules, such as rokitamycin and miocamycin, showing improved bioavailability and activity against some resistant micro-organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗