Erythromycin

The Non-Antibacterial Effects of Azithromycin and Other Macrolides on the Bronchial Epithelial Barrier and Cellular Differentiation

The respiratory epithelium maintains the barrier against inhaled harmful agents. When barrier failure occurs, as in several respiratory diseases, acute or chronic inflammation leading to destructive effects and exacerbations can occur. Macrolides are used to treat a spectrum of infections but are also known for off-label use. Some macrolides, particularly azithromycin (AZM), reduce exacerbations in chronic obstructive pulmonary disease (COPD), whereby its efficacy is thought to be due to its effects on inflammation and oxidative stress. In vitro data indicate that AZM reduces epithelial barrier failure, evidenced by increased transepithelial electrical resistance (TEER). Here, we compared the effects of macrolides on differentiation and barrier integrity in VA10 cells, a bronchial epithelial cell line for 14 and 21 days. Erythromycin, clarithromycin, roxithromycin, AZM, solithromycin, and tobramycin (an aminoglycoside) were analyzed using RNA sequencing, barrier integrity assays, and immunostaining to evaluate effects on the epithelium. All macrolides affected the gene expression of pathways involved in epithelial-to-mesenchymal transition, metabolism, and immunomodulation. Treatment with AZM, clarithromycin, and erythromycin raised TEER and induced phospholipid retention. AZM treatment was distinct in terms of enhancement of the epithelial barrier, retention of phospholipids, vesicle build-up, and its effect on gene sets related to keratinocyte differentiation and establishment of skin barrier.

Molecular mechanism of crisaborole combined with erythromycin against methicillin-resistant Staphylococcus aureus in vivo and in vitro

The widespread presence of methicillin-resistant Staphylococcus aureus (MRSA) severely threatens convenient therapeutic options in the postantibiotic era. The use of combinations of existing drugs at this stage may be a viable strategy for dealing with complex drug-resistant MRSA infections. An checkerboard MIC (Minimum Inhibitory Concentration) assay, growth curve assay, bactericidal test and scanning electron microscope (SEM) assays were performed to determine whether crisaborole (AN2728), a PDE4 inhibitor for treating atopic dermatitis (AD), produced bactericidal effect with different antibiotics. Here, we identified (AN2728) produced a significant synergistic bactericidal effect with erythromycin, cefuroxime and rifampicin against different bacterial strains of Staphylococcus aureus (S. aureus), especially MRSA (FIC < 0.5) (p < 0.05). Transcriptome analysis, bacterial biofilm assay and several kit assays revealed that AN2728 could also simultaneously affect the membrane and transporter capacity of MRSA. Moreover, in a mouse skin infection model of MRSA, the combination of AN2728 and erythromycin showed remarkable treatment benefits, as shown by significantly reduced bacterial loading (p < 0.05), pathological lesions of the skin and an obvious anti-inflammatory effect (p < 0.05). To our knowledge, this study is the first to establish that AN2728 can cooperate with antibiotics such as erythromycin to completely kill MRSA and that AN2728 can be used to extend the usage life of different antibiotics to address the inevitability of severe MRSA infection.

Heteroleptic Coumarin-Based Silver(I) Complexes: Possible New Antimicrobial Agents

Heteroleptic coumarin-based silver(I) complexes with improved solubility profiles were synthesised using either triphenylphosphine or an N-heterocyclic carbene as adduct ligands, and were fully characterised using IR and NMR spectroscopy, elemental analysis, and, where possible, X-ray crystallography. The triphenylphosphine adducts formed well-resolved structures, where the oxyacetate ligands asymmetrically chelated the silver(I) ion in a bidentate chelating mode, and the silver(I) ion was also bound to two triphenylphosphine ligands. The solubility profile and photostability of the adducts were considerably improved compared to those of previously isolated simple coumarin silver(I) complexes. Analysis of the coumarin N-heterocyclic carbene(NHC) silver(I) adduct indicated that it likely formed as a complex aggregate species with an overall stoichiometry of 1:1:1 coumarin:Ag(I):NHC. The Kirby Bauer assay and broth microdilution assays were used to assess the silver(I) complexes' and adducts' antimicrobial activity against pathogenic strains of Pseudomonas aeruginosa, Escherichia coli, and MRSA. Interestingly, the formation of more soluble complexes did not increase the activity of the silver(I) complexes and, in effect, made them less effective antimicrobial agents, particularly against Escherichia coli and Pseudomonas aeruginosa, although they retained their activity against MRSA.

Environmental factors influencing the development and spread of resistance in erythromycin-resistant streptococcus pneumoniae

Bacterial drug resistance is becoming increasingly serious, this study aims to investigate the relationship between the resistance rate of erythromycin-resistant Streptococcus pneumoniae (SP) and reasons for the epidemic under complex geographical and climatic factors in China. Data spanning from 2014 to 2021, including drug resistance rates, isolate rates, meteorological variables, and demographic statistics, were collected from the China Antimicrobial Resistance Monitoring System, the China Statistical Yearbook and China Meteorological Website. Our analysis involved nonparametric tests and the construction of multifaceted regression models for rigorous multivariate analysis. Single-factor analysis revealed significant differences in the resistance rate and isolate rate of erythromycin-resistant SP across different regions characterized by Hu Huanyong lines or different climate types. Multivariate regression analysis indicated positive correlations between the drug resistance rate and temperature, Subtropical climate, Gross Domestic Product (GDP), Hu Huanyong line, and the highest temperature in the past period (Tm); the isolate rate showed a positive correlation with regional GDP and a negative correlation with monsoon climate. The model developed in this study provides valuable insights into the resistance rate and potential relationships of erythromycin-resistant SP under complex meteorological conditions in China.

Methyltransferase Domain-Focused Genome Mining for Fungal Polyketide Synthases

A comparison of substrate-binding site amino acid residues in the C-methyltransferase (MT) domains of fungal nonreducing polyketide synthases (NR-PKSs) suggests that these residues are correlated with the methylation modes used by the PKSs. A PKS, designated as AsbPKS, with substrate-binding site residues distinct from those of other known PKSs is focused on. The characterization of AsbPKS revealed that it yields an isocoumarin derivative, anhydrosclerotinin B (1), the biosynthesis of which involves a previously unreported methylation pattern. This study demonstrates the utility of MT domain-focused genome mining for the discovery of PKSs with new functions.

Assessing the Ecotoxicity of Eight Widely Used Antibiotics on River Microbial Communities

Global prevalence of antibiotic residues (ABX) in rivers requires ecotoxicological impact assessment. River microbial communities serve as effective bioindicators for this purpose. We quantified the effects of eight commonly used ABXs on a freshwater river microbial community using Biolog EcoPlates™, enabling the assessment of growth and physiological profile changes. Microbial community characterization involved 16S rRNA gene sequencing. The river community structure was representative of aquatic ecosystems, with the prevalence of Cyanobacteria, Proteobacteria, Actinobacteria, and Bacteroidetes. Our findings reveal that all ABXs at 100 µg/mL reduced microbial community growth and metabolic capacity, particularly for polymers, carbohydrates, carboxylic, and ketonic acids. Chloramphenicol, erythromycin, and gentamicin exhibited the highest toxicity, with chloramphenicol notably impairing the metabolism of all studied metabolite groups. At lower concentrations (1 µg/mL), some ABXs slightly enhanced growth and the capacity to metabolize substrates, such as carbohydrates, carboxylic, and ketonic acids, and amines, except for amoxicillin, which decreased the metabolic capacity across all metabolites. We explored potential correlations between physicochemical parameters and drug mechanisms to understand drug bioavailability. Acute toxicity effects at the river-detected low concentrations (ng/L) are unlikely. However, they may disrupt microbial communities in aquatic ecosystems. The utilization of a wide array of genetically characterized microbial communities, as opposed to a single species, enables a better understanding of the impact of ABXs on complex river ecosystems.

Antimicrobial Transformation Products in the Aquatic Environment: Global Occurrence, Ecotoxicological Risks, and Potential of Antibiotic Resistance

The global spread of antimicrobial resistance (AMR) is concerning for the health of humans, animals, and the environment in a One Health perspective. Assessments of AMR and associated environmental hazards mostly focus on antimicrobial parent compounds, while largely overlooking their transformation products (TPs). This review lists antimicrobial TPs identified in surface water environments and examines their potential for AMR promotion, ecological risk, as well as human health and environmental hazards using in silico models. Our review also summarizes the key transformation compartments of TPs, related pathways for TPs reaching surface waters and methodologies for studying the fate of TPs. The 56 antimicrobial TPs covered by the review were prioritized via scoring and ranking of various risk and hazard parameters. Most data on occurrences to date have been reported in Europe, while little is known about antibiotic TPs in Africa, Central and South America, Asia, and Oceania. Occurrence data on antiviral TPs and other antibacterial TPs are even scarcer. We propose evaluation of structural similarity between parent compounds and TPs for TP risk assessment. We predicted a risk of AMR for 13 TPs, especially TPs of tetracyclines and macrolides. We estimated the ecotoxicological effect concentrations of TPs from the experimental effect data of the parent chemical for bacteria, algae and water fleas, scaled by potency differences predicted by quantitative structure-activity relationships (QSARs) for baseline toxicity and a scaling factor for structural similarity. Inclusion of TPs in mixtures with their parent increased the ecological risk quotient over the threshold of one for 7 of the 24 antimicrobials included in this analysis, while only one parent had a risk quotient above one. Thirteen TPs, from which 6 were macrolide TPs, posed a risk to at least one of the three tested species. There were 12/21 TPs identified that are likely to exhibit a similar or higher level of mutagenicity/carcinogenicity, respectively, than their parent compound, with tetracycline TPs often showing increased mutagenicity. Most TPs with increased carcinogenicity belonged to sulfonamides. Most of the TPs were predicted to be mobile but not bioaccumulative, and 14 were predicted to be persistent. The six highest-priority TPs originated from the tetracycline antibiotic family and antivirals. This review, and in particular our ranking of antimicrobial TPs of concern, can support authorities in planning related intervention strategies and source mitigation of antimicrobials toward a sustainable future.

Strictinin: A Key Ingredient of Tea

Strictinin is a relatively tiny ellagitannin, which is found in many plants as a minor constituent. Catechins are known as the major constituents in the young leaves of most tea plants, while strictinin was found as a major constituent in the Pu'er tea plant. In some Pu'er tea varieties, strictinin was identified as the most abundant phenolic compound rather than catechins. In the past decade, strictinin was demonstrated to possess several functional activities, including antiviral, antibacterial, anti-obesity, laxative, anticaries, anti-allergic, antipsoriatic, antihyperuricemia, antidiabetic, and anticancer effects. These functional activities were in accordance with the therapeutic effects empirically perceived for Pu'er tea. Evidently, strictinin is the key ingredient in Pu'er tea that acts as a herbal medicine. In functionally-based applications, an instant powder of Pu'er tea infusion was formulated as an active raw material to be supplemented in food, cosmetics, and beverages; a new type of tea named Bitter Citrus Tzen Tea was developed by combining three teas empirically consumed to expel the cold, and new edible oral care products were designed for caries prevention by supplementation with Pu'er tea extract. More functional activities and practical applications of strictinin are scientifically anticipated in follow-up research.

Preparation and evaluation in vitro and in vivo of pristinamycin enteric-coated granules based on albumin nanoparticles

CONTEXT

The purpose of this study was to prepare enteric-coated particles based on albumin nanoparticles (NPs) using a mixture of PI_A albumin NPs freeze-dried powder (PA-PI_A) and PII_A albumin NPs freeze-dried powder (PA-PII_A) to improve the bioavailability effect of pristinamycin.

OBJECTIVE

This is the first study on the preparation of pristinamycin into enteric-coated granules based on albumin NPs, and our study has effectively improved the bioavailability of pristinamycin and ensured its safety.

METHODS

Pristinamycin albumin enteric-coated granules (PAEGs) were prepared by hybrid wet granulation. The characterizations of albumin NPs were performed by in vitro and in vivo studies of PAEGs. The assays were analyzed using zeta-sizer, transmission electron microscopy, high-performance liquid chromatography, and a fully automated biochemical index analyzer.

RESULTS

The morphology of NPs was close to spherical. PI_A-NPs and PII_A-NPs respectively had a zeta potential of (-24.33 ± 0.75) mV and (+7.30 ± 0.27) mV and mean size of (251.91 ± 19.64) nm and (232.83 ± 22.61) nm. The release of PI_A and PII_A from PAEGs in the artificial gastrointestinal fluid was as high as 58.46% and 87.79%. In the experimental group of oral PAEGs, PI_A and PII_A were AUC_(0-t) (3.68 ± 0.58) mg·L^-1·h^-1 and (2.81 ± 1.06) mg·L^-1·h^-1. The results of aspartate aminotransferase and alanine aminotransferase biochemical indices showed that there was no significant difference between the experimental and normal groups of oral PAEGs.

CONCLUSION

The PAEGs significantly increased the release of PI_A and PII_A in simulated intestinal fluid and improved the bioavailability. The oral administration of PAEGs may not damage the liver of rats. We hope that our study will promote its industrial development or clinical application.

Impact of eight widely consumed antibiotics on the growth and physiological profile of natural soil microbial communities

Antibiotics' (ATBs) occurrence in soil ecosystems has a relevant effect in the structure and functionality of edaphic microbial communities, mainly because of their amendment with manure and biosolids that alter their key ecological functions. In this study, the impact of eight widely consumed ATBs on a natural soil microbial community, characterized through 16 S rRNA gene sequencing, was evaluated. Changes induced by the ATBs in the growth of the soil microbiota and in the community-level physiological profiling (CLPP), using Biolog EcoPlates™, were measured as endpoint. The eight assayed ATBs lead to a significant decrease in the growth of soil microbial communities in a dose-dependent way, ordered by its effect as follows: chloramphenicol > gentamycin > erythromycin > ampicillin > penicillin > amoxicillin > tetracycline > streptomycin. Chloramphenicol, gentamycin, and erythromycin adversely affected the physiological profile of the soil community, especially its ability to metabolize amino acids, carboxylic and ketonic acids and polymers. The analysis of the relationship between the physico-chemical properties of ATBs, as well as their mechanism of action, revealed that, except for the aminoglycosides, each ATB is influenced by a different physico-chemical parameters, even for ATBs of the same family. Significant effects were detected from 100 μg mL to 1, concentrations that can be found in digested sludge, biosolids and even in fertilized soils after repeated application of manure, so cumulative and long-term effects of these antibiotics on soil environment cannot be ruled out.

The Progress of Global Antimicrobial Resistance Governance and Its Implication to China: A Review

China has great potential for engaging in global actions on antimicrobial resistance (AMR) control. This study aims to summarize the process of global AMR governance and provide relevant policy recommendations on how China could take more initiative in the global AMR governance. We searched for academic articles and official document published or issued before December 2020 in e-journal databases, official websites of major organizations, and the relevant national ministries. This review revealed that global action on AMR control has experienced three stages: (1) The beginning stage (1980s and 1990s) when actions were mainly sponsored by high-income countries and AMR surveillance was focused on hospitals; (2) The rapid development stage (2000-2010) when global AMR governance began to concentrate on joint actions in multi-sectors, and developing countries were gradually involved in global actions; (3) The comprehensive stage (2011 to present) when global actions on AMR have covered various fields in different countries. China's AMR governance has fallen behind at the beginning but recently began to catch up with the global trend. The central government should take a far-fetched view, act decisively and positively towards the global efforts of addressing AMR to play a more active and greater role on the international stage.

Nonantimicrobial Actions of Macrolides: Overview and Perspectives for Future Development

Macrolides are among the most widely prescribed broad spectrum antibacterials, particularly for respiratory infections. It is now recognized that these drugs, in particular azithromycin, also exert time-dependent immunomodulatory actions that contribute to their therapeutic benefit in both infectious and other chronic inflammatory diseases. Their increased chronic use in airway inflammation and, more recently, of azithromycin in COVID-19, however, has led to a rise in bacterial resistance. An additional crucial aspect of chronic airway inflammation, such as chronic obstructive pulmonary disease, as well as other inflammatory disorders, is the loss of epithelial barrier protection against pathogens and pollutants. In recent years, azithromycin has been shown with time to enhance the barrier properties of airway epithelial cells, an action that makes an important contribution to its therapeutic efficacy. In this article, we review the background and evidence for various immunomodulatory and time-dependent actions of macrolides on inflammatory processes and on the epithelium and highlight novel nonantibacterial macrolides that are being studied for immunomodulatory and barrier-strengthening properties to circumvent the risk of bacterial resistance that occurs with macrolide antibacterials. We also briefly review the clinical effects of macrolides in respiratory and other inflammatory diseases associated with epithelial injury and propose that the beneficial epithelial effects of nonantibacterial azithromycin derivatives in chronic inflammation, even given prophylactically, are likely to gain increasing attention in the future. SIGNIFICANCE STATEMENT: Based on its immunomodulatory properties and ability to enhance the protective role of the lung epithelium against pathogens, azithromycin has proven superior to other macrolides in treating chronic respiratory inflammation. A nonantibiotic azithromycin derivative is likely to offer prophylactic benefits against inflammation and epithelial damage of differing causes while preserving the use of macrolides as antibiotics.

Oral administration of erythromycin decreases RNA toxicity in myotonic dystrophy

OBJECTIVE

Myotonic dystrophy type 1 (DM1) is caused by the expansion of a CTG repeat in the 3' untranslated region of DMPK. The transcripts containing an expanded CUG repeat (CUG (exp)) result in a toxic gain-of-function by forming ribonuclear foci that sequester the alternative splicing factor muscleblind-like 1 (MBNL1). Although several small molecules reportedly ameliorate RNA toxicity, none are ready for clinical use because of the lack of safety data. Here, we undertook a drug-repositioning screen to identify a safe and effective small molecule for upcoming clinical trials of DM1.

METHODS

We examined the potency of small molecules in inhibiting the interaction between CUG (exp) and MBNL1 by in vitro sequestration and fluorescent titration assays. We studied the effect of lead compounds in DM1 model cells by evaluating foci reduction and splicing rescue. We also tested their effects on missplicing and myotonia in DM1 model mice.

RESULTS

Of the 20 FDA-approved small molecules tested, erythromycin showed the highest affinity to CUG (exp) and a capacity to inhibit its binding to MBNL1. Erythromycin decreased foci formation and rescued missplicing in DM1 cell models. Both systemic and oral administration of erythromycin in the DM1 model mice showed splicing reversal and improvement of myotonia with no toxicity. Long-term oral administration of erythromycin at the dose used in humans also improved the splicing abnormality in the DM1 model mice.

INTERPRETATION

Oral erythromycin treatment, which has been widely used in humans with excellent tolerability, may be a promising therapy for DM1.

Mutant Alleles of lptD Increase the Permeability of Pseudomonas aeruginosa and Define Determinants of Intrinsic Resistance to Antibiotics

Gram-negative bacteria provide a particular challenge to antibacterial drug discovery due to their cell envelope structure. Compound entry is impeded by the lipopolysaccharide (LPS) of the outer membrane (OM), and those molecules that overcome this barrier are often expelled by multidrug efflux pumps. Understanding how efflux and permeability affect the ability of a compound to reach its target is paramount to translating in vitro biochemical potency to cellular bioactivity. Herein, a suite of Pseudomonas aeruginosa strains were constructed in either a wild-type or efflux-null background in which mutations were engineered in LptD, the final protein involved in LPS transport to the OM. These mutants were demonstrated to be defective in LPS transport, resulting in compromised barrier function. Using isogenic strain sets harboring these newly created alleles, we were able to define the contributions of permeability and efflux to the intrinsic resistance of P. aeruginosa to a variety of antibiotics. These strains will be useful in the design and optimization of future antibiotics against Gram-negative pathogens.

The STEP method (statistical test of equivalent pathways): application to pharmaceuticals

The STEP method (Statistical Test of Equivalent Pathways), recently developed to determine primary and secondary fragmentation in the MS/MS of peptides and carbohydrates, is applied in the current study to common pharmaceutical antibiotics. The classification of product ions as primary or secondary is then utilized to construct genealogy diagrams that aid in the structural characterization of the product ions. Four compounds were subjected to the MS/MS conditions used for the STEP method, and the method was used to correctly identify primary and secondary ions in three of the four pharmaceuticals. Calculated STEP values for erythromycin did not match previously characterized fragmentation assignments. This provided an opportunity to explore potential limitations of STEP analysis. It was determined that inaccurate STEP assignments could result, if the starting compound is classified as "fragile", because fragile ions, such as erythromycin can produce abnormally low STEP ratios. While this finding represents a limitation of using the STEP method to determine whether product ions are due to primary or secondary fragmentation for fragile ions, it suggests the possibility of identifying the presence of "fragile ions" by STEP analysis.

Current use of anti-infectives in dermatology

Dermatologic diseases encompass a broad category of pathologic situations. Infection remains a significant aspect of the pathology faced in patient encounters, and it is natural to expect that anti-infectives play a major element in the armamentarium utilized by dermatologists. Aside from the treatment of the classic bacterial and fungal infections, there are now new uses for antiviral agents to help suppress recurrent disease, such as herpes simplex. There is also the novel approach of using anti-infectives, or agents that have been thought to have antimicrobial activity, to treat inflammatory diseases. This review describes anti-infectives, beginning with common antibiotics used to treat bacterial infections. The discussion will then cover the current use of antivirals. Finally, the description of antifungals will be separated, starting with the oral agents and ending with the topical antimycotics. The use of anti-infectives in tropical dermatology has been purposefully left out, and perhaps should be the subject of a separate review. Cutaneous bacterial infections consist chiefly of those microorganisms that colonize the skin, such as species of staphylococcus and streptococcus. Propionibacterium acnes and certain other anaerobes can be involved in folliculitis, pyodermas and in chronic conditions such as hidradenitis suppurativa.

Comparative tolerability of erythromycin and newer macrolide antibacterials in paediatric patients

The macrolides are a well established group of antibacterials frequently used in general practice. The most frequently used macrolides in paediatric patients are erythromycin, a naturally occurring compound, and clarithromycin and azithromycin, recently developed macrolides. Overall adverse effect rates of 7 to 26% for erythromycin, 14 to 26% for clarithromycin, and 6 to 27% for azithromycin have been described in children. Adverse gastrointestinal effects, including nausea, vomiting, diarrhoea and abdominal cramps, are the most common problems in children. Allergic reactions, hepatotoxicity, ototoxicity and adverse effects involving the central and peripheral nervous systems have also been observed in children. Stevens-Johnson, Schonlein-Henoch and Churg-Strauss syndromes have been rarely described in children. Treatment-related laboratory abnormalities have been recorded in 2 to 4% of erythromycin- and in 0 to 1% of both clarithromycin- and azithromycin-treated children. Elevation in liver function tests was the most common abnormality cited. Increased macrolide use in children in recent years has resulted in a growing potential for drug interactions between them and other pharmacologically active agents via the inhibition of cytochrome P450 (CYP) microsomal enzymes. Drug interactions with theophylline, cyclosporin, carbamazepine, terfenadine and warfarin limit erythromycin use. Clarithromycin is a weak inducer of CYP and exhibits fewer drug-drug interactions than erythromycin. However, its use with theophylline, carbamazepine and terfenadine is contraindicated. In contrast, no significant interactions have been reported with azithromycin to date. Macrolides have been proven to be well tolerated in the treatment of upper and lower respiratory tract infections, skin and soft tissue infections, and also in less frequent infections occurring in paediatric patients. In addition, clarithromycin and azithromycin have shown good tolerability profiles in immunocompromised paediatric patients. In conclusion, macrolides antibacterials have proven to be well tolerated in paediatric patients. Although the incidence of adverse effects is similar with the use of erythromycin and the newer macrolides, drug interactions occur significantly less when clarithromycin or azithromycin are administered.

Endothelial cell compatibility of clarithromycin for intravenous use

OBJECTIVES

Tolerance of intravenously applied clarithromycin has been tested on marginal ear veins of rabbits. Use of human umbilical venous endothelial cells (HUVEC) for testing antibiotic solutions for intravenous compatibility provides a valuable alternate model.

DESIGN AND METHODS

In order to evaluate the effect of clarithromycin on intracellular purines, reflecting cell viability, energy production, signal transduction and DNA/RNA synthesis, intracellular adenosine 5' triphosphate (ATP), adenosine 5' diphosphate (ADP), guanosine 5' triphosphate (GTP), and guanosine 5' diphosphate (GDP) levels were measured by means of high performance liquid chromatography (HPLC).

RESULTS

Incubation of cells with 2 mg/mL clarithromycin resulted in a rapid decrease of the intracellular ATP from 12.6 +/- 1.1 to 8.87 +/- 0.82 nmol/million cells or 1.5 +/- 0.6 nmol/million cells, after 20 or 60 min, respectively. In addition, ADP was extensively depleted. Purine nucleotide profiles were markedly different following exposure to 1 mg/mL clarithromycin. There was no significant decline of intracellular high energy phosphate levels after 20 min.

CONCLUSION

These results show that clarithromycin has a better endothelial compatibility if diluted to a final concentration of 1 mg/mL. These data are in line with our clinical observations that the occurrence of phlebitis could be minimized by diluting the manufacturers' preparation of clarithromycin to 1 mg/mL.

Macrolide antibiotics in paediatric infectious diseases

Erythromycin and other macrolides have enjoyed a renaissance in the 1970s, 1980s and 1990s secondary to the discovery of "new' pathogens such as Chlamydia, Legionella, Campylobacter and Mycoplasma spp. Erythromycin is an important therapeutic agent in the paediatric age group for several reasons: (a) it exhibits proven efficacy for a wide range of infections (upper and lower respiratory tract infections, skin/skin structure infections, prophylaxis of endocarditis/acute rheumatic fever/ophthalmia neonatorum and pre-colonic surgery, campylobacteriosis, chlamydial and ureaplasmal infections, diphtheria, whooping cough, streptococcal pharyngitis) and gastrointestinal (GI) dysmotility states; (b) intravenous formulations are widely available; and (c) it is available in a number of formulations as a generic product, which is likely to result in significant cost savings. Nevertheless, erythromycin and similar earlier macrolides are characterised by a number of drawbacks including a narrow spectrum of antimicrobial activity, unfavourable pharmacokinetic properties and poor GI tolerability. Newer macrolides such as clarithromycin and azithromycin are useful in serving the needs of paediatric patients who are erythromycin-intolerant or who have infections caused by organisms that are intrinsically erythromycin-resistant, or for which a high percentage of strains are resistant (e.g. Haemophilus influenzae, Helicobacter pylori, Mycobacterium avium complex). In addition, these newer macrolides may be considered as alternatives to oral amoxicillin-clavulanic acid, second or third generation cephalosporins, or erythromycin plus sulphonamide in this patient population. Selection between specific macrolides and between macrolides and other antibiotics in the paediatric population is likely to depend, at least for the immediate future, on separate comparisons of product availability, cost, effectiveness and tolerability profiles.

Multi-centre collaborative study for the in vitro evaluation of new macrolides dirithromycin and erythromycylamine. Australian Group for Antimicrobial Resistance (AGAR)

A national study was conducted to determine the in vitro activity of 2 newer macrolides, dirithromycin and erythromycylamine compared with that of erythromycin, tetracycline and penicillin. Nineteen major teaching hospitals participated in the study. Minimal Inhibitory Concentrations (MICs) were determined by agar dilution, mostly using Iso-Sensitest Agar and an inoculum of 10(4) cells per spot. 2284 clinically significant strains were isolated in late 1991 and early 1992, comprising 1736 Gram-positive cocci, 355 Haemophilus influenzae, 97 Moraxella catarrhalis, 32 Listeria monocytogenes, 25 Neisseria meningitidis and 39 Neisseria gonorrhoeae were tested. The study indicates that dirithromycin and erythromycylamine possess antibacterial activity equivalent to that of erythromycin against most Gram-positive cocci and M. catarrhalis. Strains resistant to erythromycin were also resistant to dirithromycin and to erythromycylamine. Tetracycline was as active as the macrolides against both penicillin-resistant and penicillin-susceptible strains of Staphylococcus aureus. Coagulase-negative penicillin-resistant staphylococci, compared with tetracycline, were relatively resistant to the macrolides. H. influenzae was less susceptible than the Gram-positive cocci.

Semi-synthetic derivatives of erythromycin

Semi-synthetic derivatives of erythromycin have played an important role in antimicrobial chemotherapy. First generation derivatives such as 2'-esters and acid-addition salts significantly improved the chemical stability and oral bioavailability of erythromycin. A second generation of erythronolide-modified derivatives: roxithromycin, clarithromycin, azithromycin, dirithromycin and flurithromycin, have been synthesized and have exhibited significant improvements in pharmacokinetic and/or microbiological features. In addition, erythromycin itself has expanded its utility as an effective antibiotic against a variety of newly emerged pathogens. As a result of these developments, macrolide antibiotics have enjoyed a resurgence in clinical interest and use during the past half-dozen years, and semi-synthetic derivatives of erythromycin should continue to be important contributors to this macrolide renaissance. Despite these recent successes, other useful niches for macrolide antibiotics will remain unfilled. Consequently, the search for new semi-synthetic derivatives of erythromycin possessing even better antimicrobial properties should be pursued.

Comparative in vitro activity of clarithromycin. Spanish Collaborative Group

The activity in vitro of clarithromycin, a new macrolide, was compared to that of various antibiotics in tests using 3,880 clinical isolates. Clarithromycin was two times more active than erythromycin against Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, streptococci of groups C, G and F, Brucella melitensis, Legionella pneumophila and Mycoplasma spp., 16 times more active against Ureaplasma urealyticum and 2 to 4 times less active against Campylobacter spp. In general, clarithromycin showed intrinsic activity 2 to 4 times higher than that of roxithromycin and 4 to 8 times higher than that of miocamycin. Cross-resistance was found between the macrolides. Clarithromycin was bactericidal against Streptococcus spp. and Haemophilus influenzae.

Possible risk for cardiac arrhythmia related to intravenous erythromycin

OBJECTIVE

To evaluate the incidence of prolongation of the rate-corrected electrocardiographic QT interval (QTc) and of ventricular arrhythmia associated with intravenous administration of erythromycin lactobionate.

DESIGN

A consecutive series of 7 critically ill patients treated with intravenous erythromycin for severe pneumonia.

SETTING

A medical intensive care unit of a university hospital.

MEASUREMENTS AND RESULTS

Registration of QTc duration before and after intravenous administration of erythromycin as a short infusion. Blood chemistry, hemodynamic variables, arrhythmias, and co-medications were recorded. Evaluation of at least 10 ECG intervals by 2 experienced investigators who were blinded as to the time of drug administration. If several measurements were performed in the same patient, only the mean value was used for further analysis. During 12 of 13 drug administrations studied in 7 patients QTc prolongation was observed. The extent of QTc prolongation was significantly correlated with the infusion rate (mg/min, r = 0.765, p = 0.05). In 3 patients ventricular arrhythmia occurred in close temporal relation to the erythromycin infusion; two of them developed ventricular fibrillation shortly after the first and second dose of erythromycin, respectively, and died within 3 h.

CONCLUSION

In critically ill patients erythromycin-induced QTc prolongation is a frequent pharmacologic effect correlated with erythromycin infusion rate. To avoid changes in electrocardiographic intervals and thereby possibly potentially life-threatening ventricular arrhythmia administration with the lowest possible infusion rate and close cardiac rhythm monitoring are advisable in these patients.

Application of nanoscale packed capillary liquid chromatography (75 μm id) and capillary zone electrophoresis/electrospray ionization mass spectrometry to the analysis of macrolide antibiotics

Nanoscale separation techniques, nanoscale packed capillary columns (75 μm id), and capillary zone electrophoresis (CZE), on-line with electrospray mass spectrometry (ESI/MS), were applied to the separation of a series of ten macrolide antibiotics. Both techniques use sub-microliter-per-minute flow rates through the analytical column and therefore require an electrospray probe that incorporates coaxial sheath flow. Positive ion electrospray mass spectra of these compounds yielded mainly protonated molecules. Fragmentation to yield structurally significant fragment ions was achieved by collision-induced dissociation (CID) at increased skimmer voltages. Separations were achieved using both techniques, with CZE/ESI/MS showing improved peak shapes and detection limits combined with faster analysis times. Nanoscale packed capillary columns provided better chromatographic resolution and was less susceptible to peak broadening caused by overloading of the analytes.

Pulmonary disposition of antimicrobial agents: methodological considerations

Images

The new macrolide antibiotics: azithromycin, clarithromycin, dirithromycin, and roxithromycin

OBJECTIVE

To review the chemistry, antimicrobial spectrum, pharmacokinetics, clinical trials, adverse effects, and drug interactions of four new macrolide antibiotics: azithromycin, clarithromycin, dirithromycin, and roxithromycin.

DATA SOURCES

Information was obtained from comparative clinical trials, abstracts, conference proceedings, and review articles. Indexing terms included azithromycin, clarithromycin, dirithromycin, erythromycin, roxithromycin, and macrolide antibiotics.

STUDY SELECTION

Emphasis was placed on comparative clinical trials involving the new macrolide antibiotics.

DATA EXTRACTION

Data from human studies published in the English language were evaluated. Trials were assessed by sample size, macrolide dosage regimen, and therapeutic response.

DATA SYNTHESIS

The erythromycins have gained widespread use in treating a variety of infections. Although they are effective, limitations include the need to administer four times a day and the intolerable adverse gastrointestinal effects. Four of the more extensively studied agents, azithromycin, clarithromycin, dirithromycin, and roxithromycin, are currently being studied in patients. Based on the studies to date, the newer macrolides may offer several advantages over erythromycin, including: (1) greater antimicrobial activity against certain organisms; (2) longer elimination half-life, thus allowing less frequent administration; and (3) lower incidence of adverse gastrointestinal effects.

CONCLUSIONS

The new macrolide antibiotics appear to offer an improvement over erythromycin. Definitive conclusions about the role of these drugs should await completion of ongoing clinical studies.

Comparison of three-day and five-day courses of azithromycin in the treatment of atypical pneumonia

This open, randomised clinical study, conducted from June 1988 to December 1989, included 84 patients with clinical and radiological findings of atypical pneumonia. All patients were treated with a total dose of 1.5 g azithromycin, a new azalide antibiotic. In Group I, azithromycin was administered for three days (500 mg once daily). In Group II, azithromycin was administered for five days (250 mg b.i.d. on day 1, followed by 250 mg once daily on days 2 to 5). Causative pathogens were identified by serological methods. Of the 41 patients in Group I, Mycoplasma pneumoniae, Chlamydia psittaci and Coxiella burnetti were identified in 19, 4 and 3 patients, respectively. In Group II there were 43 patients; Mycoplasma pneumoniae was identified in 24, Chlamydia psittaci in 4 and Coxiella burnetti in 3. Only patients with known causative pathogens were included in the evaluation of clinical efficacy. All patients were clinically cured by day 5; most of the patients became afebrile within 48 h of starting treatment. Side effects were observed in one patient in Group I and in one patient in Group II. The results suggest that a 1.5 g total dose of azithromycin is equally effective when administered as a three- or five-day regimen for the treatment of atypical pneumonia.

Clinical microbiology of azithromycin

Azithromycin contains an aza-methyl substitution in the 15-membered aglycone ring and as such it is the prototype antibiotic of the azalide class, similar in mechanism of activity to the macrolides. It demonstrates a broad spectrum of activity against many aerobic and anaerobic Gram-positive species, and also inhibits a number of important aerobic and anaerobic Gram-negative bacteria. Significantly, azithromycin shows good activity against Haemophilus influenzae, an organism against which older macrolide antibiotics have proved disappointing. It is highly effective in inhibiting clinically significant intracellular pathogens such as Chlamydia trachomatis and Legionella. Bactericidal activity is seen for certain streptococci and for H. influenzae. Closely linked with azithromycin's microbiologic activity are its novel pharmacokinetics. Azithromycin moves rapidly from blood to tissue compartments where it remains for prolonged periods. Although serum concentrations remain low, the levels attained in the tissues (often greater than 2 mg/kg) are higher than the minimum inhibitory concentration for many common pathogens, and delivery of drug to infection sites by phagocytic cells contributes to these concentrations. This penetration into eukaryotic and prokaryotic cells may be responsible for azithromycin's expanded spectrum of activity, particularly against intracellular organisms. The use of antibiotic blood levels as breakpoints for susceptibility would appear to be inappropriate in the case of azalides. Rather, levels of drug at the tissue site of infection should be considered as guides to predicting efficacy. The in vitro activity of azithromycin, together with its unique tissue pharmacodynamics, define an agent that should demonstrate utility in infections of the respiratory tract, skin and skin structures, and certain sexually transmitted diseases.

Synthesis and antimicrobial evaluation of dirithromycin (AS-E 136; LY237216), a new macrolide antibiotic derived from erythromycin

Dirithromycin is a 9-N-11-O-oxazine derivative which is formed by condensation of 9(S)-erythromycylamine with 2-(2-methoxyethoxy)acetaldehyde. Dirithromycin is hydrolyzed, either under acidic conditions or in vivo, to its major active metabolite, 9(S)-erythromycylamine. The antimicrobial spectrum of dirithromycin is similar to that of erythromycin; both antibiotics are active against gram-positive bacteria, Legionella spp., Helicobacter pylori, and Chlamydia trachomatis. Comparable results were obtained for each antibiotic in MIC and MBC determinations and in the potential development of resistance in vitro. The effects of human serum, bacterial growth media, test methodology, and inoculum size on MICs were similar for each antibiotic. In standard mouse protection studies, dirithromycin was more efficacious than erythromycin against experimental infections after subcutaneous administration of antibiotic. These results were consistent with pharmacokinetic studies in rodents, which showed that dirithromycin gave more persistent concentrations of antibiotic in serum and tissues than were achieved with erythromycin. These studies indicate that dirithromycin possesses antimicrobial activity comparable to that of erythromycin in vitro but is more active than erythromycin in vivo, which may be attributable to the persistence of antimicrobial activity in the tissue(s) of the test animals.

MICs and MBCs of chemotherapeutic agents against Renibacterium salmoninarum

The efficacies of 21 chemotherapeutic agents for controlling bacterial kidney disease were evaluated. The bactericidal and/or bacteriostatic effects of these drugs were tested against 11 Renibacterium salmoninarum strains with different origins. The most effective compounds displaying both bacteriostatic and bactericidal activity for all the isolates were tetracycline and erythromycin, with MICs ranging from less than 0.62 to 10.95 micrograms/ml for tetracycline and from less than 0.62 to 5.47 micrograms/ml for erythromycin. Whereas tetracycline showed identical MICs and MBCs, erythromycin showed bactericidal effects at concentrations of 5.47 to 21.87 micrograms/ml. Similarly, cefazolin and tiamulin proved to be very effective bactericidal compounds against the majority of R. salmoninarum isolates, with MBCs for 90% of the strains tested of 21.87 and 10.95 micrograms/ml, respectively. Neither nitrofuranes, quinolones, nor sulfonamides showed inhibitory effects on the growth of the strains.

Ca2+ dependence of motilide-induced contractions in rabbit duodenal muscle strips in vitro

Recent studies suggested that certain erythromycin A (EM-A) derivatives are motilin receptor agonists. As proposed by Itoh they may be called "motilides". We have investigated the Ca2(+)-dependence of contractions induced by two potent motilides, ME-34 [de(N-methyl) 8,9-anhydroeryhtromycin A 6,9-hemiacetal] and EM-523 [de(N-methyl)-N-ethyl-8,9-anhydroerythromycin A 6,9-hemiacetal], in duodenal tissues and compared the results with those previously obtained with motilin. Isometric and isotonic contractile responses of isolated longitudinal muscle sheets from the rabbit duodenum were tested under normal, Ca2(+)-free and depolarizing conditions. Prior to stimulation with motilides, the maximal response to acetylcholine was recorded and all responses were always expressed as a percentage of this response. Both motilides induced contractions in normally polarized tissue, with an EC50 of 26 +/- 5 nM for ME-34 (n = 7), and 27 +/- 5 nM for EM-523 (n = 16) and maximal responses of respectively 88 +/- 4% and 80 +/- 3%. Like motilin, both compounds induced an 'extra'-contraction in depolarized tissues. The EM-523 response in 140 mM K+ under isotonic conditions was 84 +/- 3% (n = 5) at 10(-5) M, with an EC50 that was shifted to 65 +/- 18 nM. Similar figures were obtained for ME-34. When Ca2+ was added to Ca2(+)-depleted strips, half-maximal Ca2+ values (in mM) were 1.10 +/- 0.11 (n = 9) for EM-523 and 1.13 +/- 0.12 (n = 3) for ME-34, as compared with 1.12 +/- 0.13 (n = 7) for motilin and 2.8 +/- 1.1 (n = 9) for K+. Both ME-34 and EM-523 also induced a transient contraction in Ca2(+)-free solutions under isometric conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Using erythromycin. Some helpful observations

Erythromycin is a very safe antibiotic that is effective against a wide variety of common and uncommon bacterial infections. Several formulations are available, each with a different absorption rate and dosing profile. The most common side effect of erythromycin is gastrointestinal intolerance, which appears to be related to disruption of intestinal motility. Gastrointestinal tolerance may be improved by limiting daily doses to less than 4 g; temporarily decreasing the total daily dose; using small doses of liquid suspension every 2, 3, or 4 hours; taking the medication with milk or food; and drinking water every 15 minutes two or three times after each dose. These measures may, in turn, improve compliance and efficacy in affected patients.

Therapy of gram-positive bacterial infections

This article considers the important features of gram-positive bacteria that relate to chemotherapy and the clinical pharmacology of the drugs of choice for treating these infections.