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PubMed1996

Evaluation of in vitro spectra of activity of azithromycin, clarithromycin, and erythromycin tested against strains of Neisseria gonorrhoeae by reference agar dilution, disk diffusion, and Etest methods.

The macrolide-azilide susceptibility testing (agar dilution, disk diffusion, Etest) criteria for 105 Neisseria gonorrhoeae strains were evaluated. In addition, the potencies of azithromycin, clarithromycin, and erythromycin were studied. The most active macrolide-azilide agent was azithromycin (MIC at which 90% of the isolates are inhibited [MIC90], 0.5 microgram/ml) compared with clarithromycin (MIC90, 1.5 to 2 micrograms/ml) and erythromycin (MIC90, 2 to 4 micrograms/ml). The Etest (AB Biodisk, Solna, Sweden) was observed to produce MIC results very similar to those of the reference agar dilution test (GC agar base), with 100% of the results within 1 log2 dilution step of the reference MICs. The disk diffusion test zone diameters for all three drugs correlated at an acceptable level (r = -0.81 to -0.92) with the reference agar dilution MICs. Interpretive criteria for susceptibility were proposed for azithromycin at a MIC of < or = 2 micrograms/ml and a disk diffusion test zone of > or = 25 mm. No category for resistance was proposed because of the paucity of strains for which MICs were > 2 micrograms/ml. These tentative criteria should be further validated by correlations with clinical trial data for gonococcal strains (as they emerge) that have azithromycin MICs above the proposed susceptible category range.

Agar↗
PubMed1998

Detection of point mutations associated with resistance of Helicobacter pylori to clarithromycin by hybridization in liquid phase.

When the standard procedure for determining antibiotic susceptibility of bacteria is used, the results are delayed, especially for bacteria that grow slowly, such as Helicobacter pylori. Treatment for this bacterium may involve clarithromycin, a compound for which resistance has been associated with point mutations on the 23S rRNA gene. This resistance is currently found in organisms isolated from 0 to 15% of patients and jeopardizes the success of the treatment. We have designed a test involving amplification and colorimetric hybridization in the liquid phase to detect the mutation at the molecular level. First, four reference strains, including the wild type and three strains with the mutations A2143C, A2143G, and A2144G, were used to optimize the method. Amplification was carried out with primers previously published. The amplified products were added to probe-coated microtiter wells. A DNA enzyme immunoassay was used to detect the hybrids. The optimal conditions of the hybridization were defined for each probe. Nineteen H. pylori strains resistant to clarithromycin and 22 susceptible according to phenotypic data were submitted to restriction with BsaI and BbsI, and part of the 23S rRNA gene was sequenced in order to determine the mutation involved for the resistant strains. The new assay showed a complete correlation with the reference methods, except for one strain. Cross-hybridizations as well as application of the reaction to other bacteria did not lead to optical densities higher than the cutoff values chosen with the receiving operating characteristic curve. This method can be easily standardized and gives a result within a day. Its application directly to the biopsy specimens or infected gastric juice is planned in the future.

Anti-Bacterial Agents↗
PubMed1998

Standardized BACTEC method to measure clarithromycin susceptibility of Mycobacterium genavense.

A standardized clarithromycin susceptibility test for Mycobacterium genavense is reported. The BACTEC radiometric broth dilution test method recommended for Mycobacterium avium complex was modified to develop a reliable and reproducible procedure. Test development involved optimization of medium pH and inoculum densities for antibiotic vials as well as growth control vials. MIC control organisms included Mycobacterium simiae, Mycobacterium avium, and Mycobacterium xenopi. Growth control vials required two to three inoculum dilutions, which varied for each species. Clarithromycin MICs and MBCs for 12 isolates and 1 colonial variant of M. genavense ranged from < or = 0.06 to 0.25 microg/ml.

Anti-Bacterial Agents↗
PubMed2000

Detection of clarithromycin-resistant helicobacter pylori strains by a preferential homoduplex formation assay.

It has been shown that resistance to clarithromycin, a major cause of failure in Helicobacter pylori eradication therapy, is associated with point mutations in the 23S rRNA gene. We sought to apply the preferential homoduplex formation assay (PHFA), a novel technique for the efficient detection of point mutations, to detection of the mutations. PHFA was performed on streptavidin-coated microtiter plates with biotin- and dinitrophenyl-labeled amplicons to detect the wild-type gene or each mutant gene. DNA samples were extracted from gastric juice specimens of 412 patients with H. pylori infection and were applied to the assay. The detection threshold of PHFA was as few as 10 gene copies. The sensitivity of PHFA for the detection of H. pylori infection was higher than those of culture and the rapid urease test. A total of 337 (81.8%) samples had the wild-type gene, 38 (9.2%) had the A2144G mutation, and 37 (9.0%) contained both the wild type and a mutation (A2144G in 30 samples, A2143G in 5 samples, and A2143G plus A2144G in 2 samples). About half the strains isolated from patients with mixed infection were susceptible by the agar dilution method (MIC, <0.1 mg/liter). Therefore, PHFA can detect clarithromycin-resistant H. pylori strains, even in patients with mixed infections with the wild type, that are not detectable by the agar dilution method.

Adult↗
PubMed2001

Evaluation of clarithromycin resistance and cagA and vacA genotyping of Helicobacter pylori strains from the west of Ireland using line probe assays.

The prevalence of clarithromycin resistance-associated mutations, the cytotoxin-associated gene (cagA), and the various vacuolating cytotoxin (vacA) genotypes was determined in 50 gastric biopsy specimens from Helicobacter pylori-infected patients, using line probe assays. The clarithromycin resistance-associated mutation A2143G was detected in H. pylori strains from 26% of the specimens, which suggested that the high rate of H. pylori treatment failure in Ireland may be partly attributable to the presence of these mutations. All strains examined carried the vacA s1 genotype, and 76% were cagA positive. Of these 50 specimens, 13 (26%) carried H. pylori strains with vacA midregion genotype m1, 29 (58%) carried strains that were m2, 1 (2%) was infected by a strain that was positive for both m1 and m2, and 7 (14%) carried strains that could not be typed.

Anti-Bacterial Agents↗
PubMed2003

Real-time PCR assay for rapid and accurate detection of point mutations conferring resistance to clarithromycin in Helicobacter pylori.

The main cause of failure of Helicobacter pylori eradication therapy is resistance to clarithromycin. The resistance is due to three point mutations in two positions on the 23S rRNA (A2142C, A2142G, and A2143G). Our aim was to develop a rapid and accurate method to detect these mutations directly on biopsy specimens. We developed a real-time PCR that included a simultaneous detection of the amplicons by hybridization of two probes labeled with LC-Red and fluorescein by using the fluorescence resonance energy transfer (FRET) technology and melting curve analysis with the LightCycler thermocycler. The assay was first applied successfully on reference strains, reference plasmids, and H. pylori-negative biopsies. Biopsies from 200 patients having failed a first eradication attempt and for whom the H. pylori strain was available were then tested with the new assay. A result was obtained in 199 cases; a single genotype was detected in 157 cases, two genotypes were detected in 41 cases, and three genotypes were detected in one case. There were, in total, seven discrepancies between the real-time PCR and the phenotypic method of determination of clarithromycin susceptibility, and in an additional four cases the two phenotypic methods were in disagreement. PCR-restriction fragment length polymorphism was applied to a sampling of biopsies, including all of the cases with multiple genotypes and all the cases with discrepant results. Finally, in four cases with discrepant results, the real-time PCR detected the resistant population at a concentration so low that it could not be detected by the phenotypic method, while in three cases other mutations could be involved. This assay had an accuracy at least as satisfactory as that of the phenotypic tests and could be performed within 2 h, allowing it to be used before the administration of therapy in the case of a first H. pylori eradication.

Anti-Bacterial Agents↗
PubMed2005

Evaluation of seaFAST, a rapid fluorescent in situ hybridization test, for detection of Helicobacter pylori and resistance to clarithromycin in paraffin-embedded biopsy sections.

A commercially available rapid fluorescent in situ hybridization (FISH) test, (seaFAST H. pylori Combi-Kit; SeaPro Theranostics International, Lelystad, The Netherlands) was used to simultaneously detect the presence of Helicobacter pylori and determine clarithromycin susceptibility in paraffin-embedded biopsy sections. The FISH method was found to be 97% sensitive, 94% specific for the detection of H. pylori and comparable to agar dilution for the detection of resistance to clarithromycin.

Anti-Bacterial Agents↗
PubMed1998

Clarithromycin induced digoxin toxicity.

A case of digoxin poisoning following the co-administration of digoxin and clarithromycin in a 28 year old male is described. Since the aetiology of chronic digoxin poisoning is often unclear, clinicians should be aware of the potential drug-drug interaction between digoxin and clarithromycin.

Adult↗
PubMed2003

Clarithromycin inhibits overproduction of muc5ac core protein in murine model of diffuse panbronchiolitis.

Long-term treatment of macrolide antibiotics is considered an effective treatment for diffuse panbronchiolitis (DPB). Although hypersecretion is a common feature of this disease, and it is known that macrolides inhibit mucin production, the mechanism of the effect on mucin production is unclear. The aim of our study was to determine the production of muc5ac core protein, a major core protein of mucin in airway secretion, and the effect of clarithromycin treatment on such production in a mouse model mimicking DPB. Alcian blue-periodic acid-Schiff-positive cells were detected in the lungs of Pseudomonas aeruginosa-infected mice. Western blots of these mice showed muc5ac glycoprotein at day 1 and increased progressively from day 4 to day 14 after inoculation of bacteria. Clarithromycin (10 mg. kg-1. day-1 for 7 days) significantly reduced the muc5ac expression at both the mRNA and protein levels. To investigate the role of molecules upstream in muc5ac regulation, we examined the role of mitogen-activated protein kinase. Extracellular signal-regulated kinase 1/2 phosphorylation increased in the infected lung and decreased after treatment. Our results suggest that overproduction of muc5ac plays an important role in the pathogenesis of DPB and that clinical improvement following macrolide therapy seems to involve, at least in part, its inhibition of mucin overproduction, through modulation of intracellular signal transduction.

Animals↗
PubMed2000

Omeprazole once or twice daily with clarithromycin and metronidazole for Helicobacter pylori.

BACKGROUND: Triple therapy for one week with omeprazole, clarithromycin and metronidazole (OCM) is accepted worldwide as a first line therapy for Helicobacter pylori eradication. It is unclear whether omeprazole needs to be given once or twice daily. OBJECTIVES: To assess the efficacy and safety of these regimens in a single-centre, Canadian practice. METHODS: Histologically proven H pylori-positive patients were treated for seven days with clarithromycin 250 mg bid and metronidazole 500 mg bid, and randomly allocated to omeprazole 20 mg either once or twice daily in this open, cohort study. Endoscopy with histology (two antrum and two body biopsies, Giemsa stain) was done four weeks or longer after the pills were completed to assess H pylori eradication. RESULTS: Whether omeprazole was given once or twice daily, eradication was high and the same in both arms. All-patients-treated eradication was 85% (39 of 46 in the omeprazole once daily group and 41 of 48 in the omeprazole twice daily group) and intent-to-treat eradication was 80% (39 of 49 in the omeprazole once daily group and 41 of 51 in the omeprazole twice daily group). Side effects were frequently seen, suffered by 65% to 69% of patients treated. However, these were mild and compliance was high, with 94% of patients taking all of their pills. Mild side effects included loose stools, taste disturbance, nausea, headache and upper or lower gastrointestinal gas. Only one patient (1%) from the omeprazole once daily arm stopped taking metronidazole due to excessive perspiring. CONCLUSIONS: In this community practice, OCM triple therapy was effective whether omeprazole was given once or twice daily. For those with financial constraint, omeprazole 20 mg once daily can be considered. The regimens were well tolerated without serious adverse events.

Anti-Bacterial Agents↗
PubMedDate not supplied

Effect of clarithromycin on Pseudomonas aeruginosa biofilms.

Using an experimental in vitro culture system, we investigated the effect of clarithromycin on biofilm formation by a leucine-requiring Pseudomonas aeruginosa mutant strain (HU1). Biofilm formation on celldesks in a chemically defined medium was assessed by viable cell count as well as by measurement of glycocalyx production and scanning electron-microscopic observation. Cells proliferated exponentially until day 3 and remained stationary afterwards. The amount of glycocalyx, simultaneously semiquantified, showed a linear increase from day 1 to day 12. Scanning electron microscopy revealed firm biofilms on day 5. Three different concentrations of Clarithromycin (CAM) (minimum inhibitory concentration MIC 64 microg/ml) were added continuously at the early and late phases of biofilm formation, and the antibiofilm effect of CAM was evaluated by the changes in cell count and glycocalyx production. CAM was effective on biofilms at 100 microg/ml but neither at 1 nor at 10 microg/ml. It is suggested that glycocalyx production started following bacterial multiplication and continued even after the cells had entered the stationary phase to form mature biofilms. No antibiofilm effect of CAM was observed at sub-MIC.

Anti-Bacterial Agents↗
PubMed1999

Resolution of gastritis induced by Helicobacter pylori 4-5 weeks after successful eradication of infection using a triple therapy regimen of pantoprazole, amoxycillin and clarithromycin for one week.

UNLABELLED: This open-label study was designed to determine the extent of histological resolution of gastritis induced by Helicobacter pylori infection 4-5 weeks after successful eradication of the infection. Eradication was achieved using a triple therapy regimen consisting of a twice daily dose of pantoprazole 40 mg, clarithromycin 500 mg, and amoxicillin 1,000 mg taken for 1 week only. No other medications were given thereafter. Four biopsies were processed for histological examination of each patient, two from the antral and two from the corporeal mucosa, first at the start of the study and then again 4 weeks after cessation of the medication trial. Scoring for H. pylori colonization and the severity of gastritis was determined for each patient according to the Sydney system. 53 of 57 patients in this study had their H. pylori infection successfully eradicated by the regimen mentioned and could be histologically evaluated. According to the severity of gastritis in the antral mucosa, patients were studied in 3 groups: mild, moderate and severe gastritis. 17 of 19 cases with mild gastritis showed complete resolution of the inflammation, with residual inflammatory changes persisting in 2 cases only. 22 of the 26 cases with moderate gastritis showed almost complete recovery except for minor residual inflammatory changes as judged by irregularity of intracytoplasmic mucine storage. Persistent residual inflammatory changes in the lamina propria were detected in 4 cases. Of the 8 cases with severe gastritis 5 showed subsidence of the inflammatory changes, but the mucosa in these cases revealed some scarring, distortion of the glandular epithelium and atrophy. In 3 cases residual inflammation persisted. CONCLUSION: One-week therapy with a twice daily dose of pantoprazole 40 mg, clarithromycin 500 mg and amoxicillin 1,000 mg, used to eradicate H. pylori causing active inflammation of the gastric mucosa, has led to subsidence of the acute inflammatory changes in all the cases with residual inflammation persisting in 17%. Severe gastritis may cause irreparable damage to the gastric mucosa. The density of H. pylori colonization does not appear to be related to the severity of gastritis, nor to the successful eradication achieved.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1999

One-week triple regime therapy consisting of pantoprazole, amoxicillin and clarithromycin for cure of Helicobacter pylori-associated upper gastrointestinal diseases.

This study was designed to determine the efficacy and safety of 1-week triple therapy regime consisting of pantoprazole, amoxicillin and clarithromycin in the cure of Helicobacter pylori infection leading to duodenal ulcer disease and/or gastritis. Sixty-one patients (47 males, 14 females with a mean age of 34 years) belonging to different ethnic groups suffering from H. pylori-associated duodenal ulcer and/or gastritis for an average of 2.46 years were recruited. Having satisfied primary selection criteria, patients received pantoprazole 40 mg b.i.d., clarithromycin 500 mg b.i.d. and amoxicillin 1,000 mg b.i.d. for 7 days. All medications were stopped there after H. pylori eradication was determined 4-6 weeks after treatment by a repeat endoscopy, a rapid urease test, H. pylori culture and histology assessment as indicators of cure. All three tests must be negative to consider the infection to have been successfully eradicated. Fifty-seven patients completed the efficacy analysis per protocol. Dramatic symptomatic improvement was noted in most patients immediately after stopping treatment and it was sustained at 6 weeks. At the end of the study, the healing rate of duodenal ulcers (complete re-epithelialization) following 1-week treatment only, as indicated above, and without any maintenance therapy was 66.7%, that of gastritis was 55.7%, and that of erosions was 64.3%. The overall eradication rate for H. pylori, however, was 93% (95% CI 83.0-98.1%). Furthermore, histologic evaluation revealed a remarkable resolution in the activity of gastritis in all the patients who had successful eradication of the infection.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2000

Dose-related stimulatory effect of clarithromycin on interdigestive gastroduodenal motility.

BACKGROUND/AIMS: The effect on interdigestive gastroduodenal motility of different doses of clarithromycin, an antibiotic commonly used for Helicobacter pylori eradication, has been investigated. METHODS: Gastroduodenal motility was recorded by means of a low-compliance manometric system in 15 healthy subjects. Thirty minutes after the first phase III of the migrating motor complex, clarithromycin (CLA) was infused intravenously at a dose of 100 mg in 5, 250 mg in 5 and 400 mg in 5 subjects, randomly and in a double-blind manner, continuing the recording for at least 1 h. A further study was carried out on 10 subjects, 5 of whom received 50 mg CLA and 5 normal saline with the same modalities. RESULTS: After 100 mg CLA a premature gastroduodenal phase III ensued in all cases, which showed a duration, propagation velocity and wave frequency not significantly different from the spontaneous one and was followed by a clear phase I. A premature gastroduodenal phase-III-like activity occurred in 3 cases of 250 mg CLA and 2 cases after 400 mg CLA, followed by a very short or absent phase I and characterized by a long duration of the antral phase III, while in the remaining cases a long-lasting sequence of about 1/min of antral waves propagated to the duodenum appeared, sometimes preceded by an antral phase-III-like activity not propagated to the duodenum. After 50 mg CLA a premature phase III appeared in 2 cases, while a not premature phase III appeared in 2 cases after saline. CONCLUSION: CLA shows a dose-related stimulatory effect on interdigestive gastroduodenal motility varying from the initiation of a typical phase III to a prolonged sequence of gastroduodenal coordinated waves. These motor effects of CLA suggest potential therapeutic applications.

Adolescent↗
PubMedDate not supplied

A new model examining intracellular and extracellular activity of amoxicillin, azithromycin, and clarithromycin in infected cells.

An in vitro infection model was created using a suspension of macrophages, polymorphonuclear leukocytes, lymphocytes, fibroblasts, and human serum to which pathogen and antibiotic were added. Separate intracellular and extracellular antibiotic concentrations and activity against Staphylococcus aureus and Legionella pneumophila were assessed for three antimicrobial agents: amoxicillin, azithromycin and clarithromycin. Amoxicillin was found almost exclusively in extracellular fluid, where it was active; intracellularly, it was ineffective. Azithromycin, in contrast, was primarily concentrated and active intracellularly, with little activity in extracellular fluid. Clarithromycin was present in both compartments and possessed significant activity both intracellularly and extracellularly.

Amoxicillin↗
PubMed1992

Clarithromycin minimal inhibitory and bactericidal concentrations against Mycobacterium avium.

Minimal inhibitory and bactericidal concentrations (MIC and MBC) of clarithromycin were determined with 49 Mycobacterium avium strains isolated from patients with acquired immunodeficiency syndrome. The inhibitory activity depended on the pH of the medium: the drug was more active at pH 7.4 and less active at pH 5.0, with activity at pH 6.8 in an intermediate position. The broth-determined MIC found at pH 7.4 were 0.25 and 0.5 micrograms/ml for most strains. The agar-determined MIC for most strains ranged from 1.0 to 4.0 micrograms/ml. The MBC of the drug were 8- to 64-fold higher than the MIC, which indicates that the efficacy of clarithromycin can be associated with its inhibitory rather than its bactericidal activity.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Inhibition of intracellular growth of Staphylococcus aureus by exposure of infected human monocytes to clarithromycin and azithromycin.

The direct effect of clarithromycin and azithromycin on human polymorphonuclear leukocyte (PMN) functions and their intracellular activity against Staphylococcus aureus, phagocytosed by human monocytes, were studied. The presence of both antibiotics, in the range of concentrations from 0.25 to 20 micrograms/ml, did not affect chemotaxis, opsonized-zymosan phagocytosis, respiratory burst measured by nitroblue tetrazolium reduction and phorbol myristate acetate-induced superoxide production, or the microbicidal activity of human PMNs against Candida albicans. Both macrolides were bactericidal against staphylococci in the monocyte system, while bacteriostatic activity was found in cell free system. At concentrations equal to the minimum inhibitory concentrations (MICs) (0.75 and 0.1 respectively for azithromycin and clarithromycin) more than 99% of intraphagocytic S. aureus were killed after 24 h incubation. Increasing the concentrations of each drug above the MICs (5 and 10 MICs) did not alter the killing rate of intracellular bacteria. Moreover, no differences between the intracellular bioactivity of these antibiotics were demonstrated, despite their different uptake kinetics.

Azithromycin↗
PubMed1999

Clarithromycin: pharmacokinetic and pharmacodynamic interrelationships and dosage regimen.

In the last decade three important pharmacodynamic parameters: T>MIC, Cmax/MIC and AUC/MIC, have been shown to correlate well with in-vitro antimicrobial efficacy and that found in animal models, differentiating among groups of antibiotics with diverse mechanisms of action such as exposure time or concentration-dependent effect. The macrolide antimicrobial agents display variable concentration-dependent killing, indicating the increasing importance of the Cmax parameter. Clarithromycin, whose T>MIC and AUC influence its clinical efficacy, is in an intermediate position between its progenitor, erythromycin, and the azalides. This paper reviews pharmacokinetic and pharmacodynamic characteristics of clarithromycin, examining the potential impact of these properties on the dose and the optimal interval between administrations.

Anti-Bacterial Agents↗