Teichomycins, new antibiotics from Actinoplanes teichomyceticus nov. sp. IV. Separation and characterization of the components of teichomycin (teicoplanin)

The Impact of Heterologous Regulatory Genes from Lipodepsipeptide Biosynthetic Gene Clusters on the Production of Teicoplanin and A40926

StrR-like pathway-specific transcriptional regulators (PSRs) function as activators in the biosynthesis of various antibiotics, including glycopeptides (GPAs), aminoglycosides, aminocoumarins, and ramoplanin-like lipodepsipeptides (LDPs). In particular, the roles of StrR-like PSRs have been previously investigated in the biosynthesis of streptomycin, novobiocin, GPAs like balhimycin, teicoplanin, and A40926, as well as LDP enduracidin. In the current study, we focused on StrR-like PSRs from the ramoplanin biosynthetic gene cluster (BGC) in Actinoplanes ramoplaninifer ATCC 33076 (Ramo5) and the chersinamycin BGC in Micromonospora chersina DSM 44151 (Chers28). Through the analysis of the amino acid sequences of Ramo5 and Chers28, we discovered that these proteins are phylogenetically distant from other experimentally investigated StrR PSRs, although all StrR-like PSRs found in BGCs for different antibiotics share a conserved secondary structure. To investigate whether Ramo5 and Chers28, given their phylogenetic positions, might influence the biosynthesis of other antibiotic pathways governed by StrR-like PSRs, the corresponding genes (ramo5 and chers28) were heterologously expressed in Actinoplanes teichomyceticus NRRL B-16726 and Nonomuraea gerenzanensis ATCC 39727, which produce the clinically-relevant GPAs teicoplanin and A40926, respectively. Recombinant strains of NRRL B-16726 and ATCC 39727 expressing chers28 exhibited improved antibiotic production, although the expression of ramo5 did not yield the same effect. These results demonstrate that some StrR-like PSRs can "cross-talk" between distant biosynthetic pathways and might be utilized as tools for the activation of silent BGCs regulated by StrR-like PSRs.

Development and validation of a bioanalytical assay for the measurement of total and unbound teicoplanin in human serum

BACKGROUND

The glycopeptide teicoplanin is considered first-line treatment for severe infections caused by Gram-positive bacteria. Individualized treatment of teicoplanin is gaining interest. As only protein-unbound drug is pharmacologically active, a sensitive assay measuring unbound and total teicoplanin is indispensable for pharmacological research and dose optimization.

OBJECTIVES

To develop and validate a UPLC-MS/MS method to quantify unbound and total teicoplanin in human serum.

METHODS

The developed assay was validated according to the ICH guideline M10 on Bioanalytical Method Validation and study sample analysis. Unbound teicoplanin was obtained by ultrafiltration. The assay was cross-validated with a quantitative microsphere (QMS) immunoassay in a side-by-side comparison using 40 patient samples.

RESULTS

With the developed and validated method, all main teicoplanin components (A2-1, A2-2/A2-3, A2-4/A2-5 and A3-1) can be quantified. Total run time was 5.5 min. Concentration range was 2.5-150 mg/L for total and 0.1-25 mg/L for unbound teicoplanin. Precision (coefficient of variation) and accuracy (bias) of total teicoplanin were 5.97% and 107%, respectively, and 7.17% and 108%, respectively, for unbound teicoplanin.Bland-Altman analysis showed total concentrations measured with the UPLC-MS/MS method were equivalent to the results of the QMS immunoassay. A total of 188 samples from 30 patients admitted to the ICU and haematology department were measured; total concentrations ranged between 2.92 and 98.5 mg/L, and unbound concentrations ranged between 0.37 and 30.7 mg/L.

CONCLUSIONS

The developed method provided rapid, precise and accurate measurement of unbound and total teicoplanin. The developed method is now routinely applied in pharmacological research and clinical practice.

Cross-Talking of Pathway-Specific Regulators in Glycopeptide Antibiotics (Teicoplanin and A40926) Production

Teicoplanin and A40926 (natural precursor of dalbavancin) are clinically relevant glycopeptide antibiotics (GPAs) produced by Actinoplanes teichomyceticus NRRL B-16726 and Nonomuraea gerenzanensis ATCC 39727. Their biosynthetic enzymes are coded within large biosynthetic gene clusters (BGCs), named tei for teicoplanin and dbv for A40926, whose expression is strictly regulated by pathway-specific transcriptional regulators (PSRs), coded by cluster-situated regulatory genes (CSRGs). Herein, we investigated the "cross-talk" between the CSRGs from tei and dbv, through the analysis of GPA production levels in A. teichomyceticus and N. gerenzanensis strains, with knockouts of CSRGs cross-complemented by the expression of heterologous CSRGs. We demonstrated that Tei15* and Dbv4 StrR-like PSRs, although orthologous, were not completely interchangeable: tei15* and dbv4 were only partially able or unable to cross-complement N. gerenzanensis knocked out in dbv4 and A. teichomyceticus knocked out in tei15*, implying that the DNA-binding properties of these PSRs are more different in vivo than it was believed before. At the same time, the unrelated LuxR-like PSRs Tei16* and Dbv3 were able to cross-complement corresponding N. gerenzanensis knocked out in dbv3 and A. teichomyceticus knocked out in tei16*. Moreover, the heterologous expression of dbv3 in A. teichomyceticus led to a significant increase in teicoplanin production. Although the molecular background of these events merits further investigations, our results contribute to a deeper understanding of GPA biosynthesis regulation and offer novel biotechnological tools to improve their production.

Optimal Use and Need for Therapeutic Drug Monitoring of Teicoplanin in Children: A Systematic Review

BACKGROUND

Teicoplanin is a glycopeptide antimicrobial that treats serious invasive infections caused by gram-positive bacteria, such as the methicillin-resistant Staphylococcus aureus. Despite some comparable advantages, there is no guideline or clinical recommendation for teicoplanin in the pediatric population, unlike vancomycin where abundant studies and the recently revised guideline on therapeutic drug level monitoring (TDM) exist.

METHODS

The systematic review was performed in accordance with the preferred reporting items for systematic reviews. Two authors (JSC and SHY) searched PubMed, Embase, and Cochrane Library databases using relevant terms independently.

RESULTS

Fourteen studies were finally included with a total of 1,380 patients. TDM was available in 2,739 samples collected in the nine studies. Dosing regimens varied widely, and eight studies used recommended dosing regimens. Timing for measuring TDM was mostly 72-96 hours or longer after the initiation of the first dose, which was expected to be a steady-state. The majority of studies had target trough levels of 10 µg/mL or above. Three studies reported that the clinical efficacy and treatment success rate of teicoplanin was 71.4%, 87.5%, and 88%. Adverse events associated with teicoplanin use were described in six studies with a focus on renal and/or hepatic impairment. Except for one study, no significant relation was noted between the incidence of adverse events and trough concentration.

CONCLUSION

Current evidence on teicoplanin trough levels in pediatric populations is insufficient due to heterogeneity. However, target trough levels with favorable clinical efficacy are achievable by recommended dosing regimen in the majority of patients.

Glycopeptide Antibiotic Teicoplanin Inhibits Cell Entry of SARS-CoV-2 by Suppressing the Proteolytic Activity of Cathepsin L

Since the outbreak of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), public health worldwide has been greatly threatened. The development of an effective treatment for this infection is crucial and urgent but is hampered by the incomplete understanding of the viral infection mechanisms and the lack of specific antiviral agents. We previously reported that teicoplanin, a glycopeptide antibiotic that has been commonly used in the clinic to treat bacterial infection, significantly restrained the cell entry of Ebola virus, SARS-CoV, and MERS-CoV by specifically inhibiting the activity of cathepsin L (CTSL). Here, we found that the cleavage sites of CTSL on the spike proteins of SARS-CoV-2 were highly conserved among all the variants. The treatment with teicoplanin suppressed the proteolytic activity of CTSL on spike and prevented the cellular infection of different pseudotyped SARS-CoV-2 viruses. Teicoplanin potently prevented the entry of SARS-CoV-2 into the cellular cytoplasm with an IC₅₀ of 2.038 μM for the Wuhan-Hu-1 reference strain and an IC₅₀ of 2.116 μM for the SARS-CoV-2 (D614G) variant. The pre-treatment of teicoplanin also prevented SARS-CoV-2 infection in hACE2 mice. In summary, our data reveal that CTSL is required for both SARS-CoV-2 and SARS-CoV infection and demonstrate the therapeutic potential of teicoplanin for universal anti-CoVs intervention.

Strain Improvement and Strain Maintenance Revisited. The Use of Actinoplanes teichomyceticus ATCC 31121 Protoplasts in the Identification of Candidates for Enhanced Teicoplanin Production

Multicellular cooperation in actinomycetes is a division of labor-based beneficial trait where phenotypically specialized clonal subpopulations, or genetically distinct lineages, perform complementary tasks. The division of labor improves the access to nutrients and optimizes reproductive and vegetative tasks while reducing the costly production of secondary metabolites and/or of secreted enzymes. In this study, we took advantage of the possibility to isolate genetically distinct lineages deriving from the division of labor, for the isolation of heterogeneous teicoplanin producer phenotypes from Actinoplanes teichomyceticus ATCC 31121. In order to efficiently separate phenotypes and associated genomes, we produced and regenerated protoplasts. This approach turned out to be a rapid and effective strain improvement method, as it allowed the identification of those phenotypes in the population that produced higher teicoplanin amounts. Interestingly, a heterogeneous teicoplanin complex productivity pattern was also identified among the clones. This study suggests that strain improvement and strain maintenance should be integrated with the use of protoplasts as a strategy to unravel the hidden industrial potential of vegetative mycelium.

Quantification of Teicoplanin Using the HPLC-UV Method for Clinical Applications in Critically Ill Patients in Korea

A high-performance liquid chromatography-ultraviolet detector (HPLC-UV) method has been used to quantify teicoplanin concentrations in human plasma. However, the limited analytical accuracy of previously bioanalytical methods for teicoplanin has given rise to uncertainty due to the use of an external standard. In this study, an internal standard (IS), polymyxin B, was applied to devise a precise, accurate, and feasible HPLC-UV method. The deproteinized plasma sample containing teicoplanin and an IS of acetonitrile was chromatographed on a C18 column with an acidic mobile phase consisting of NaH₂PO₄ buffer and acetonitrile (78:22, v/v) by isocratic elution and detection at 220 nm. The linearity was in the range 7.8–500 mg/L calculated by the ratio of the teicoplanin signal to the IS signal. This analytical method, validated by FDA guidelines with ICH Q2 (R1), was successfully applied to analyze the plasma samples of patients in the intensive care unit for treating serious resistant bacterial infectious diseases, such as those by methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. The methods suggested the potential for use in routine clinical practice for therapeutic drug monitoring of teicoplanin, providing both improved accuracy and a wide range of linearity from lower than steady-state trough concentrations (10 mg/L) to much higher concentrations.

Determination of teicoplanin in human plasma by reverse micelle mediated dispersive liquid-liquid microextraction with high performance liquid chromatography

A reverse micelle mediated dispersive liquid-liquid microextraction (RM-DLLME) combined with high performance liquid chromatography-ultraviolet detector (HPLC-UV) was developed for extraction and determination of 5 A₂ components of teicoplanin (TA_2-1, TA_2-2, TA_2-3, TA_2-4, TA_2-5) in human plasma, and the mechanism of RM-DLLME was analysed and explored. In this method, 80 µL of the reverse micelle solution of cetylpyridinium chloride/n-hexanol (15 mmol/L) was used as the extraction solvent for the separation, extraction and enrichment of the teicoplanin in plasma sample. All factors affecting the extraction efficiencies of the target analytes, such as the amounts of acetonitrile and chloroform, the type and volume of reverse micelle solution, pH and volume of sample phase, dispersant, salt addition, extraction mode and time, centrifugation rate and time, were investigated and optimized. Under the optimum conditions, the 5 A₂ components of teicoplanin achieved effective enrichment with the enrichment factors of 228-347 and obtained good linearity in the range of 0.8375-100.5 µg/mL with correlation coefficients higher than 0.9960. The limits of detection were ranged between 0.5025-3.015 µg/mL. Relative standard deviation values of the method precisions were lower than 10.6% and the average recoveries were in the range of 82.7-111.3%. The determination results of the method were demonstrated with favorable characteristics, such as high enrichment, good selectivity and sensitivity, satisfactory precision and accuracy, and this method could be employed to analysis of the teicoplanin in human plasma samples.

COVID-19 Therapeutic Options Under Investigation

Since its emergence in China in December 2019, COVID-19 has quickly spread around the globe causing a pandemic. Vaccination or the development of herd immunity seems the only way to slow down the spread of the virus; however, both are not achievable in the near future. Therefore, effective treatments to mitigate the burden of this pandemic and reduce mortality rates are urgently needed. Preclinical and clinical studies of potential antiviral and immunomodulatory compounds and molecules to identify safe and efficacious therapeutics for COVID-19 are ongoing. Two compounds, remdesivir, and dexamethasone have been so far shown to reduce COVID-19-associated death. Here, we provide a review of the potential therapeutic agents being considered for the treatment and management of COVID-19 patients.

Clinical Pharmacokinetics and Pharmacodynamics of Telavancin Compared with the Other Glycopeptides

Telavancin was discovered by modifying the chemical structure of vancomycin and belongs to the group of lipoglycopeptides. It employs its antimicrobial potential through two distinct mechanisms of action: inhibition of bacterial cell wall synthesis and induction of bacterial membrane depolarization and permeabilization. In this article we review the clinically relevant pharmacokinetic and pharmacodynamic data of telavancin. For comparison, the pharmacokinetic and pharmacodynamic data of the other glycopeptides are presented. Although, in contrast to the newer lipoglycopeptides, telavancin demonstrates a relatively short half-life and rapid total clearance, its apparent volume of distribution (V_d) is almost identical to that of dalbavancin. The accumulation of telavancin after repeated dosing is only marginal, whereas the pharmacokinetic values of the other glycopeptides show much greater differences after administration of multiple doses. Despite its high plasma-protein binding of 90% and relatively low V_d of approximately 11 L, telavancin shows near complete equilibration of the free fraction in plasma with soft tissue. The ratio of the area under the plasma concentration-time curve from time zero to 24 h (AUC₂₄) of unbound plasma concentrations to the minimal inhibitory concentration (MIC) required to inhibit growth of 90% of organisms (MIC₉₀) of Staphylococcus aureus and S. epidermidis of telavancin are sufficiently high to achieve pharmacokinetic/pharmacodynamic targets indicative for optimal bacterial killing. Considering both the AUC₂₄/MIC ratios of telavancin and the near complete equilibration of the free fraction in plasma with soft tissue, telavancin is an appropriate antimicrobial agent to treat soft tissue infections caused by Gram-positive pathogens. Although the penetration of telavancin into epithelial lining fluid (ELF) requires further investigations, the AUC₂₄/MIC ratio for S. aureus indicates that bactericidal activity in the ELF could be expected.

New semisynthetic teicoplanin derivatives have comparable in vitro activity to that of oritavancin against clinical isolates of VRE

Ten analogues of a teicoplanin pseudoaglycon derivative have been synthesized with the aim of optimizing the in vitro activity of the compound against VanA type vancomycin resistant enterococci (VRE) isolated from hospitalized patients. Teicoplanin, vancomycin, and oritavancin were used as reference antibiotics for the antibacterial evaluations. One of the new derivatives exhibited far superior activity than the original compound. The in vitro MICs measured were comparable to that of oritavancin against the investigated VRE strains.

Measurement of Teicoplanin Concentration With Liquid Chromatography-Tandem Mass Spectrometry Method Demonstrates the Usefulness of Therapeutic Drug Monitoring in Hematologic Patient Populations

BACKGROUND

Teicoplanin is a glycopeptide antibiotic that has become increasingly popular with the spread of methicillin-resistant Staphylococcus aureus. The aim of the study was to develop and validate an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for teicoplanin, and analyze trough teicoplanin concentrations achieved in patients with hematological diseases.

METHODS

The UHPLC-MS/MS method for teicoplanin was developed, validated, and applied in a retrospective analysis of trough plasma teicoplanin concentrations from 305 patients receiving standard dose, and 17 patients receiving therapeutic drug monitoring (TDM)-guided individualized dose.

RESULTS

The linear range was 3.9-52.9 mg/L. The imprecision was less than 12%, the limits of detection and quantification were less than 0.13 and 0.72 mg/L, respectively. The sample carry-over and ion suppression were insignificant. In the standard dose group, the median teicoplanin concentrations were 7.5 mg/L (days 3-5) and 8.9 mg/L (on days 6-8); and the proportion of trough levels achieving ≥10 mg/L was 20% (days 3-5) and 38% (days 6-8), respectively. In the TDM-guided individualized dose group, median teicoplanin concentration was higher (16.9 mg/L), and the proportion of trough levels ≥10 mg/L was also higher (77%) when compared with the standard dose group.

CONCLUSIONS

Based on these results, the present UHPLC-MS/MS method can be considered suitable for routine TDM of teicoplanin. Also, based on the insufficient trough teicoplanin concentrations achieved with standard dose regimen, and the higher trough teicoplanin concentrations achieved with TDM-guided individualized dose regimen, this study highlights the importance of TDM of teicoplanin, especially in high-risk patient groups.

Old and new glycopeptide antibiotics: From product to gene and back in the post-genomic era

Glycopeptide antibiotics are drugs of last resort for treating severe infections caused by multi-drug resistant Gram-positive pathogens. First-generation glycopeptides (vancomycin and teicoplanin) are produced by soil-dwelling actinomycetes. Second-generation glycopeptides (dalbavancin, oritavancin, and telavancin) are semi-synthetic derivatives of the progenitor natural products. Herein, we cover past and present biotechnological approaches for searching for and producing old and new glycopeptide antibiotics. We review the strategies adopted to increase microbial production (from classical strain improvement to rational genetic engineering), and the recent progress in genome mining, chemoenzymatic derivatization, and combinatorial biosynthesis for expanding glycopeptide chemical diversity and tackling the never-ceasing evolution of antibiotic resistance.

Targeting a cell wall biosynthesis hot spot

Covering: up to 2017History points to the bacterial cell wall biosynthetic network as a very effective target for antibiotic intervention, and numerous natural product inhibitors have been discovered. In addition to the inhibition of enzymes involved in the multistep synthesis of the macromolecular layer, in particular, interference with membrane-bound substrates and intermediates essential for the biosynthetic reactions has proven a valuable antibacterial strategy. A prominent target within the peptidoglycan biosynthetic pathway is lipid II, which represents a particular "Achilles' heel" for antibiotic attack, as it is readily accessible on the outside of the cytoplasmic membrane. Lipid II is a unique non-protein target that is one of the structurally most conserved molecules in bacterial cells. Notably, lipid II is more than just a target molecule, since sequestration of the cell wall precursor may be combined with additional antibiotic activities, such as the disruption of membrane integrity or disintegration of membrane-bound multi-enzyme machineries. Within the membrane bilayer lipid II is likely organized in specific anionic phospholipid patches that form a particular "landing platform" for antibiotics. Nature has invented a variety of different "lipid II binders" of at least 5 chemical classes, and their antibiotic activities can vary substantially depending on the compounds' physicochemical properties, such as amphiphilicity and charge, and thus trigger diverse cellular effects that are decisive for antibiotic activity.

Glycopeptide resistance: Links with inorganic phosphate metabolism and cell envelope stress

Antimicrobial resistance is a critical health issue today. Many pathogens have become resistant to many or all available antibiotics and limited new antibiotics are in the pipeline. Glycopeptides are used as a 'last resort' antibiotic treatment for many bacterial infections, but worryingly, glycopeptide resistance has spread to very important pathogens such as Enterococcus faecium and Staphylococcus aureus. Bacteria confront multiple stresses in their natural environments, including nutritional starvation and the action of cell-wall stressing agents. These stresses impact bacterial susceptibility to different antimicrobials. This article aims to review the links between glycopeptide resistance and different stresses, especially those related with cell-wall biosynthesis and inorganic phosphate metabolism, and to discuss promising alternatives to classical antibiotics to avoid the problem of antimicrobial resistance.

Glycopeptide Antibiotics Potently Inhibit Cathepsin L in the Late Endosome/Lysosome and Block the Entry of Ebola Virus, Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

Ebola virus infection can cause severe hemorrhagic fever with a high mortality in humans. The outbreaks of Ebola viruses in 2014 represented the most serious Ebola epidemics in history and greatly threatened public health worldwide. The development of additional effective anti-Ebola therapeutic agents is therefore quite urgent. In this study, via high throughput screening of Food and Drug Administration-approved drugs, we identified that teicoplanin, a glycopeptide antibiotic, potently prevents the entry of Ebola envelope pseudotyped viruses into the cytoplasm. Furthermore, teicoplanin also has an inhibitory effect on transcription- and replication-competent virus-like particles, with an IC₅₀ as low as 330 nm. Comparative analysis further demonstrated that teicoplanin is able to block the entry of Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS) envelope pseudotyped viruses as well. Teicoplanin derivatives such as dalbavancin, oritavancin, and telavancin can also inhibit the entry of Ebola, MERS, and SARS viruses. Mechanistic studies showed that teicoplanin blocks Ebola virus entry by specifically inhibiting the activity of cathepsin L, opening a novel avenue for the development of additional glycopeptides as potential inhibitors of cathepsin L-dependent viruses. Notably, given that teicoplanin has routinely been used in the clinic with low toxicity, our work provides a promising prospect for the prophylaxis and treatment of Ebola, MERS, and SARS virus infection.

A comprehensive review of glycosylated bacterial natural products

A systematic analysis of all naturally-occurring glycosylated bacterial secondary metabolites reported in the scientific literature up through early 2013 is presented. This comprehensive analysis of 15 940 bacterial natural products revealed 3426 glycosides containing 344 distinct appended carbohydrates and highlights a range of unique opportunities for future biosynthetic study and glycodiversification efforts.

Pharmacokinetic analysis of antibiotic adsorption (vancomycin and teicoplanin) by the Lixelle extracorporeal unit

PURPOSE

The pharmacokinetic properties of vancomycin (VAN) and teicoplanin (TEC) may be affected by adsorption during hemofiltration as well as hemoperfusion therapies. The aim of this in vitro study was to investigate VAN and TEC removal adsorption kinetics with mass balance analysis by direct hemoperfusion (DHP) with the Lixelle S-35 cartridge (Lixelle, Kaneka Corporation, Tokyo).

METHODS

Mock DHP was performed for 120 min using VAN and TEC solutions (46.08 ± 0.81 and 74.79 ± 1.24 mg/l per N = 6). Clinical plasma antibiotic concentrations were circulated in a closed circuit simulating DHP using an adsorption column (Lixelle S-35) at flow rate of 250 ml/min. Samples were collected at 10, 60, and 120 min through both arterial and venous ports; drug levels were measured with particle enhanced turbidimetric inhibition immunoassay and fluorescence polarization immunoassay. All tests were performed in triplicate.

RESULTS

Results subsequent to DHP at the primary assessment interval for VAN mass was 49.06 ± 1.47 mg, indicating a significant reduction of the starting mass (94.74 ± 1.63 mg). The observed reduction of TEC levels greatly exceeded that of VAN at the first interval (10 min). At 120 min of DHP, the estimated mass adsorption of VAN was 45.68 ± 2.26 mg, while the mesured total TEC mass adsorbed was 126.86 ± 0.91 mg.

CONCLUSIONS

A VAN adsorption plateau indicating the VAN loading dose may be required in patients receiving DHP with the Lixelle S-35. The total TEC mass was adsorbed subsequent to 60 min of circulation, so the loading dose should be closely considered. In addition, the Lixelle S-35 may represent an option as a rescue therapy in accidental overdose of TEC.

Multicomponent antibiotic substances produced by fermentation: implications for regulatory authorities, critically ill patients and generics

Teicoplanin and polymyxin E (colistin) are antibiotics consisting of multiple, closely related subcomponents, produced by fermentation. The principal components comprise a complex mixture of chemically related, active substances (teicoplanin A(2-1)-A(2-5) and polymyxin E(1-2), respectively), which might be required to be present in specific ratios to ensure optimal antibacterial and clinical efficacy. These subcomponents differ in their fatty acid and amino acid composition and, as such, the lipophilic and protein binding characteristics differ between components. This has therapeutic implications for critically ill patients, as the volume of distribution of the teicoplanin A2 and polymyxin E analogues at the onset of an intravenous infusion may impact on expected pharmacokinetics and influence outcome.

Chemical tailoring of teicoplanin with site-selective reactions

Semisynthesis of natural product derivatives combines the power of fermentation with orthogonal chemical reactions. Yet, chemical modification of complex structures represents an unmet challenge, as poor selectivity often undermines efficiency. The complex antibiotic teicoplanin eradicates bacterial infections. However, as resistance emerges, the demand for improved analogues grows. We have discovered chemical reactions that achieve site-selective alteration of teicoplanin. Utilizing peptide-based additives that alter reaction selectivities, certain bromo-teicoplanins are accessible. These new compounds are also scaffolds for selective cross-coupling reactions, enabling further molecular diversification. These studies enable two-step access to glycopeptide analogues not available through either biosynthesis or rapid total chemical synthesis alone. The new compounds exhibit a spectrum of activities, revealing that selective chemical alteration of teicoplanin may lead to analogues with attenuated or enhanced antibacterial properties, in particular against vancomycin- and teicoplanin-resistant strains.

Structure of the complex between teicoplanin and a bacterial cell-wall peptide: use of a carrier-protein approach

Multidrug-resistant bacterial infections are commonly treated with glycopeptide antibiotics such as teicoplanin. This drug inhibits bacterial cell-wall biosynthesis by binding and sequestering a cell-wall precursor: a D-alanine-containing peptide. A carrier-protein strategy was used to crystallize the complex of teicoplanin and its target peptide by fusing the cell-wall peptide to either MBP or ubiquitin via native chemical ligation and subsequently crystallizing the protein-peptide-antibiotic complex. The 2.05 Å resolution MBP-peptide-teicoplanin structure shows that teicoplanin recognizes its ligand through a combination of five hydrogen bonds and multiple van der Waals interactions. Comparison of this teicoplanin structure with that of unliganded teicoplanin reveals a flexibility in the antibiotic peptide backbone that has significant implications for ligand recognition. Diffraction experiments revealed an X-ray-induced dechlorination of the sixth amino acid of the antibiotic; it is shown that teicoplanin is significantly more radiation-sensitive than other similar antibiotics and that ligand binding increases radiosensitivity. Insights derived from this new teicoplanin structure may contribute to the development of next-generation antibacterials designed to overcome bacterial resistance.

Isolation and identification of chlorinated genistein from Actinoplanes sp. HBDN08 with antioxidant and antitumor activities

A strain Actinoplanes sp. HBDN08 was screened by PCR-guided method using primers derived from conserved regions of halogenase genes. A new chlorinated isoflavone, 3',8-dichlorogenistein (1), along with 8-chlorogenistein (2) were isolated from the fermentation broth of Actinoplanes sp. HBDN08. Their structures were elucidated on the basis of extensive 1D and 2D NMR as well as HRESI-MS, ESI-MS, UV, and IR spectroscopic analyses. The origin of the two compounds was also investigated by high-performance liquid chromatography (HPLC) analysis. The results demonstrated that they were not biosynthesized but derived from the biotransformation of genistein by Actinoplanes sp. HBDN08. The antioxidant activities of the isolated compounds 1 and 2 were evaluated by using the lipid peroxidation assay. Their antitumor activities were calculated according to the inhibitory rate of cell proliferation against the human breast cancer cell line MDA-MB-231. The results indicated that compounds 1 (IC(50) = 5.2 microM) and 2 (IC(50) = 7.5 microM) showed stronger antioxidant activities than genistein (IC(50) = 13.6 microM). In comparison with the antitumor activities of genistein, those of compounds 1 and 2 increased 7.7- and 2.6-fold, respectively. These results suggest that the PCR-guided screening strategy is a rapid method for obtaining halometabolite-producing strains. Moreover, these results reveal that chlorination has significant effects on the bioactivities of genistein. This could be important information for studying the structure-activity relationships of genistein.

Glycerol affects the acyl moieties of teicoplanin components produced by Actinoplanes teichomyceticus MSl2210

Teicoplanin, a glycopeptide antibiotic, is composed of five main components, denoted T-A2-1 to T-A2-5. We investigated the use of glycerol as a carbon source affecting the teicoplanin components and its acyl moieties. As a result, we show the change of teicoplanin components, as well as an increase of total teicoplanin yields, caused by the addition of glycerol to the production medium. Analysis of the total cell lipids upon the addition of glycerol also showed a corresponding change in the proportion of teicoplanin, suggesting that glycerol strongly affects a change of teicoplanin branched acyl moieties.

Quantitative determination of individual teicoplanin components in human plasma and cerebrospinal fluid by high-performance liquid chromatography with electrochemical detection

We have developed a simple, rapid and highly sensitive method for determining a plasma or cerebrospinal fluid (CSF) concentrations of individual teicoplanin components using reversed-phase high-performance liquid chromatography followed by electrochemical detection. A linear relationship was observed between concentrations and peak heights for the teicoplanin concentration range of 0.025-10microg/mL. The correlation coefficients of all standard curves were greater than or equal to 0.999. The limit of detection for the major component of teicoplanin was 1.0ng/mL (signal/noise ratio >3). Daily fluctuations of standard curves (n=5) were small, with coefficients of variation of 3.3%. The intra-assay precision was 5.9% (n=5). Inter-assay precision ranged from 2.6 to 6.8%. The method described here is suitable for clinical monitoring of teicoplanin levels in plasma or CSF level and for use in studies involving pharmacokinetics of individual teicoplanin component.

Comparison of Pharmacokinetics of Individual Teicoplanin Components in Patients

Teicoplanin is a glycopeptide antibiotic comprising six closely related major components whose activities against specific microbial species differ. In order to clarify the significance of monitoring these components separately for determining the therapeutic effectiveness of teicoplanin, we measured the total and unbound concentrations of the main teicoplanin components in plasma and the unbound fractions in patients. Teicoplanin components in plasma were determined separately by high-performance liquid chromatography following a co-extractive clean-up procedure. The concentrations of unbound teicoplanin components were estimated after plasma ultrafiltration. The plasma concentrations of the main components of teicoplanin were strongly correlated with each other. The apparent elimination rate constants of total bound and unbound teicoplanin calculated by population pharmacokinetic parameters were almost same among the components. Furthermore, the mean population unbound clearance corrected by the unbound fraction was almost the same among the components. These results suggest that monitoring the individual components of teicoplanin has no clinical significance based on the pharmacokinetics of teicoplanin.

Improved Quantitative Determination of Total and Unbound Concentrations of Six Teicoplanin Components in Human Plasma by High Performance Liquid Chromatography

Total and unbound concentrations of six teicoplanin components in human plasma were determined by high-performance liquid chromatography with a coextractive cleanup technique. Unbound concentrations of teicoplanin components were estimated after ultrafiltration of plasma. For determination of each component in plasma, plasma was deproteinized with acetonitrile and the supernatant was shaken for 60 s with chloroform under acidic conditions. The recoveries of A3-1, A2-1, A2-2, A2-3, A2-4 and A2-5 were greater than 88%. The within-day and between-day coefficients of variation were 1.3-8.8% and 2.8-11.9%, respectively. The limits of detection in ultrafiltered plasma for each component were 0.82, 2.87, 4.23, 3.36, 7.33 and 4.93 nM, respectively. A good correlation was observed between the FPIA and HPLC methods when total concentrations of each teicoplanin component in patient plasma were determined. The analytical methods established in this study are suitable for determining the total and unbound concentrations of six components of teicoplanin in human plasma and for studying the pharmacokinetics of teicoplanin components in patients.

Comparison of fluorescence polarization immunoassay and high-performance liquid chromatography methods for assay of teicoplanin: can correlation be improved?

Teicoplanin is a glycopeptide indicated in serious infections due to Staphylococcus aureus and requires monitoring and dose adjustment based on measurement of trough concentration. Measurement of teicoplanin can be carried out by the fluorescence polarization immunoassay (FPIA) method or by high-performance liquid chromatography (HPLC) methods. We aimed to compare HPLC method using the sum of the peaks of A2-2, A2-3, A2-4 and A2-5 with FPIA method. Thirty-six serum samples obtained over a 6-month period from patients treated by teicoplanin were first analyzed by a HPLC method by determining both the A2-2 peak and the sum of areas of A2-2 to A2-5 and were then stored at -20 degrees C for FPIA assay. Correlation between FPIA and HPLC A2-2 methods was as: HPLC(A2-2) = 0.694FPIA - 0.892 with r(2) = 0.93. A paired t-test revealed significant differences between the results (P < 0.001). To improve the FPIA and HPLC correlation, we performed a linear regression between FPIA and the sum of A2-2, A2-3, A2-4 and A2-5 obtained in the HPLC method: HPLC(A2-2 to A2-5) = 0.953FPIA - 0.915 with r(2) = 0.96. A paired t-test did not show any significant difference between the results of the two methods (P = 0.94). These results show a better correlation between FPIA and HPLC when the sum of A2-2 to A2-5 was used for calculations. In conclusion, HPLC(A2-2 to A2-5) must be preferred to HPLC(A2-2) for the assay of teicoplanin, even if the HPLC(A2-2 to A2-5) runtime is higher than in the HPLC(A2-2) method.

Improved production of teicoplanin using adsorbent resin in fermentations

AIMS

To use adsorbent resins in fermentations to eliminate toxic effects on growth, reduce feedback repression of production and assist in recovery of teicoplanin.

METHODS AND RESULTS

An adsorbent resin was added to the culture broth for the adsorption of teicoplanin. Amberlite XAD-16, Diaion HP-20, charcoal and silica gel were investigated as adsorbent resins. The adsorbed teicoplanin was extracted from the resin by 80% methanol after fermentation. Antibiotic activity was quantified by the disc-agar diffusion assay against Bacillus substilis, and qualitative evaluations were based on HPLC using YMC-Pack ODS-A column. Diaion HP-20 was the most effective adsorbent resin when added at a concentration of 5% (w/v) in the inoculation stage.

CONCLUSIONS

Addition of Diaion HP-20 in fermentations eliminated toxic effects on growth and reduced feedback repression of teicoplanin by adsorption. There was a 4.2-fold increase in the quantities of teicoplanin. Addition of adsorbent assisted in the recovery of teicoplanin by reducing the recovery steps.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study provide useful information for the production of teicoplanin, a glycopeptide antibiotic produced by Actinoplanes teicomyceticus. Addition of adsorbent in fermentation increased productivity of teicoplanin by more than five times.

In vitro studies of teicoplanin binding to rat tissues and erythrocytes

Teicoplanin is a large polar antibiotic with a large distribution volume (Vss = 1.2-2.8 l/kg) despite extensive binding to plasma albumin. To understand this observation, binding of 3H-teicoplanin to 10% rat tissue homogenates was determined in vitro by ultracentrifugation in the presence of teicoplanin (1-30 microg/ml). Binding and efflux from erythrocytes were also studied. The in vitro total-to-unbound tissue concentration ratio (Kpu) differed widely but for each tissue was concentration independent. Upon correction for the plasma unbound fraction, there was discrepancy between the in vitro and in vivo tissue-to-plasma concentration ratios (KP), the latter calculated from previously published tissue and plasma concentration-time data using the area method. Moreover, calculation of Vss from in vitro Kp (8.10 l/kg) overestimated the in vivo value. These results suggest that in vivo teicoplanin binds to cell membranes and enters some but not all cells, such as erythrocytes.

Chiral separation of DL-peptides and enantioselective interactions between teicoplanin and D-peptides in capillary electrophoresis

Teicoplanin has been evaluated as a selector for enantioseparation of di- and tripeptide derivatives in capillary electrophoresis. Separation variables such as type of buffer, pH, concentrations of teicoplanin and organic modifier were examined. Optimal separation conditions were obtained by means of factorial design experiments. The effects of teicoplanin concentrations below and above its critical micellar concentration (CMC) and of acetonitrile (ACN) on the separation were demonstrated. The use of a high concentration of ACN resulted not only in increased selectivity, but also in improved separation efficiency. Electroosmotic flow was observed to be largely independent of the concentrations of teicoplanin under the optimized conditions. Good repeatability of migration times was obtained. The interactions between teicoplanin and D and L peptides were studied, and it was found that, for some peptides, teicoplanin exhibited enantioselective interaction only with the D-form. Somewhat lower separation efficiencies were thus observed for the strongest interacting (D-form) peptides. Chiral separation of 15 DL-peptide derivatives was achieved in less than 10 min.

Complementation of a Streptomyces lividans Leu- mutant by the Actinoplanes teichomyceticus leuC gene

A leucine auxotroph of Streptomyces lividans (Sl), designated PC196, was unable to convert alpha-isopropylmalate into the beta-isomer. A DNA fragment from Actinoplanes teichomyceticus (At) cloned into the Streptomyces vector pIJ702 complemented PC196. Sequence analysis of the 3.0-kb insert revealed one complete ORF with high similarity to other leuC genes encoding the large subunit of isopropylmalate isomerase (IPMI), and the 5' end of a second ORF corresponding to leuD, which encodes the smaller subunit of IPMI. Further subcloning established that Sl strain PC196 is defective in the large subunit of IPMI.

Teicoplanin or vancomycin in the treatment of gram-positive infections?

The glycopeptide antibiotics vancomycin and teicoplanin have similar mechanisms of action on bacterial cell wall synthesis. Their spectra of activity are limited to Gram-positive bacteria, with the degree of bactericidal activity depending on the species of micro-organism. Staphylococcus aureus, Staphylococcus epidermis, enterococci and Clostridium difficile are generally sensitive, including methicillin-resistant strains of S. aureus and S. epidermidis. Glycopeptide resistance has recently emerged in staphylococci and enterococci. Vancomycin has a shorter half-life than teicoplanin and requires multiple dosing to maintain adequate serum levels. It can only be given by prolonged intravenous infusion over 1 h. In contrast, the pharmacokinetics of teicoplanin allow for once-daily dosing, either by rapid intravenous infusion or by the intramuscular route. The latter offers reliable absorption for patients with limited venous access and is also of benefit for out-patient therapy. Teicoplanin is a safer drug than vancomycin. It is associated with a lower incidence of nephrotoxicity or ototoxicity. Compared to vancomycin, the availability of the intramuscular route and the absence of a requirement for routine serum monitoring, together with the reduced need to treat drug-related side-effects make teicoplanin more cost-effective. It is as effective as vancomycin for most indications, is safe, easy to administer and an important agent for treating Gram-positive infections. Its role in hospitals is likely to increase if the price of drug acquisition is kept low.