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PubMed2004

Micro-broth dilution method with air-dried microplate for determining MICs of clarithromycin and amoxycillin for Helicobacter pylori isolates.

MICs of clarithromycin and amoxycillin for 253 isolates of Helicobacter pylori were measured by an air-dried microplate method and compared with the results obtained by the agar plate dilution method. The air-dried microplate method is performed by coating each well of a 96-well microplate with the test antibiotic and air-drying it. There were no marked differences between the air-dried microplate method and agar plate dilution methods in the MIC(50) and MIC(90) values or MIC ranges of clarithromycin obtained for the 253 isolates of H. pylori. More specifically, the MICs of clarithromycin for 114 (45.1 %) of the 253 isolates were the same by the air-dried microplate method as the agar plate dilution method, and the differences in the MICs of clarithromycin for a further 114 isolates (45.1 %) varied within one twofold dilution. The MICs of amoxycillin by the former method were in close agreement with the MICs obtained by the latter method: MICs of amoxycillin for 199 (78.7 %) of the 253 isolates were the same by both methods, and the differences in the MICs of amoxycillin for 42 isolates (16.6 %) varied within one twofold dilution. These results indicate that the air-dried microplate method is a useful method for determination of MICs, because the results obtained were in close agreement with those obtained by the standard agar plate dilution method. The air-dried microplate method is, therefore, a convenient and reliable method for determining the MICs of clarithromycin and amoxycillin for H. pylori isolates.

Amoxicillin↗
PubMed2006

Primary clarithromycin resistance in Italy assessed on Helicobacter pylori DNA sequences by TaqMan real-time polymerase chain reaction.

BACKGROUND: Helicobacter pylori clarithromycin resistance is increasing worldwide and different mutations are involved in its mechanisms. Recently, molecular methods have been proposed to assess these mutations. AIM: To assess prevalence of primary clarithromycin resistance in two Italian areas, and the distribution of involved mutations, by using a novel method for real-time polymerase chain reaction. METHODS: Two hundred and thirty-two H. pylori-positive patients undergoing oesophagogastroduodenoscopy in two Italian towns (Rome, centre Italy; Foggia, south Italy) were enrolled. Helicobacter pylori infection was detected by histology, rapid urease and urea breath tests. Clarithromycin resistance was assessed by TaqMan real-time polymerase chain reaction on paraffin-embedded antral biopsies. Results Primary clarithromycin resistance was detected in 62 (26.7%) patients. Its prevalence did not differ between the two areas (31.5%, centre vs. 23.3%, south; P=0.17) and between non-ulcer dyspepsia and peptic ulcer patients (28.4% vs. 20.7%, P=0.2). The A2143G point mutation was detected in 35 (56.4%) patients, A2142G in 14 (22.6%), A2142C in eight (12.9%), whilst a double mutation (A2143G plus A2142C or A2142G) was present in the remaining five (8.1%) cases. CONCLUSIONS: Our study found that primary clarithromycin resistance is highly prevalent in both central and southern Italy, and that A2143G is the most frequent point mutation involved in these areas.

Anti-Bacterial Agents↗
PubMed2003

Eradication of Helicobacter pylori by 7-day triple-therapy regimens combining pantoprazole with clarithromycin, metronidazole, or amoxicillin in patients with peptic ulcer disease: results of two double-blind, randomized studies.

AIM: To compare the short-term (7-day) safety and efficacy of two triple-therapy regimens using pantoprazole with those of two dual-therapy regimens (one with pantoprazole and one without), for Helicobacter pylori eradication in patients with peptic ulcer disease. METHODS: H. pylori infection was identified by rapid urease (CLOtest), and confirmed by histology and culture. Patients were enrolled into one of two randomized, double-blind, multicenter, parallel-group studies. In study A, patients received oral pantoprazole 40 mg, clarithromycin 500 mg, and metronidazole 500 mg (PCM); pantoprazole, clarithromycin and amoxicillin 1000 mg (PCA); or pantoprazole and clarithromycin (PC). In study B, patients received PCM, PCA, PC, or clarithromycin and metronidazole without pantoprazole (CM). Treatments were given twice daily for 7 days. H. pylori status after therapy was assessed by histology and culture at 4 weeks after completing the course of study treatment. Modified intent-to-treat (MITT; each study: n = 424, n = 512) and per-protocol (PP; each study: n = 371, n = 454) populations were analyzed. The MITT population comprised all patients whose positive H. pylori status was confirmed by culture and histology; the PP population comprised patients who also complied with > or = 85% of study medication doses. RESULTS: A total of 1016 patients were enrolled. Cure rates among patients with clarithromycin-susceptible H. pylori strains were 82 and 86% for PCM, and 72 and 71% for PCA, in studies A and B, respectively. Cure rates among patients with metronidazole-susceptible H. pylori strains were 82 and 87% for PCM, and 71 and 69% for PCA, in studies A and B, respectively. The combined eradication rates observed with the PCM regimen were superior to those of all other regimens tested. Side-effects were infrequent and mild. CONCLUSIONS: PCM had the highest overall eradication rate in these two studies examining 7-day treatment regimens. All regimens were safe and well tolerated.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1991

Effectiveness of clarithromycin and minocycline alone and in combination against experimental Mycobacterium leprae infection in mice.

As determined by the proportional bactericide method, clarithromycin had strong bactericidal activity against Mycobacterium leprae. Clarithromycin was administered to mice by gavage as 20 daily doses at dosages of 12.5 to 50 mg/kg of body weight. At a dosage of 25 mg/kg, minocycline was more active than clarithromycin at a dosage of 50 mg/kg. Additive effects were displayed with the combination of clarithromycin (50 mg/kg) and minocycline (25 mg/kg), both of which were administered daily by gavage, and of clarithromycin and minocycline, both of which were administered daily by gavage at dosages of 25 mg/kg each, with rifampin at a single oral dose of 10 mg/kg.

Animals↗
PubMed1992

Synergistic activity of clarithromycin and minocycline in an animal model of acute experimental toxoplasmosis.

The efficacy of clarithromycin in a murine model of acute toxoplasmosis was studied. Clarithromycin was administered alone and concurrently with minocycline, and efficacy was assessed by survival rates and sequential determination of parasite burden in blood, brains, and lungs. Limited protection resulted from administration of each drug alone, whereas a remarkable synergistic effect followed concurrent administration. Survival of mice treated with 200 mg of clarithromycin plus 20 mg of minocycline per kg of body weight daily was 95%; that of mice treated with 50 mg of clarithromycin plus 50 mg of minocycline per kg daily was 93%. The parasite burden in the blood and organ tissues of these mice was markedly reduced compared with that in mice treated with a single agent. In mice treated with 200 mg of clarithromycin plus 50 mg of minocycline per kg per day, survival was 100% during the 30-day experiment; no parasites were found in blood and tissues.

Animals↗
PubMed1993

In vitro and in vivo activities of the hydroxynaphthoquinone atovaquone alone or combined with pyrimethamine, sulfadiazine, clarithromycin, or minocycline against Toxoplasma gondii.

The efficacy of atovaquone alone or combined with pyrimethamine, sulfadiazine, clarithromycin, and minocycline was examined in vitro and in a murine model of acute toxoplasmosis. In vitro studies were performed with MRC5 fibroblast tissue cultures, with quantification of Toxoplasma growth by an enzyme-linked immunosorbent assay. For in vivo studies, mice were acutely infected intraperitoneally with 10(4) tachyzoites of the virulent RH strain and then treated perorally for 10 days from day 1 postinfection. The following drug regimens were investigated: atovaquone at 100 and 50 mg/kg of body weight per day and the combinations of atovaquone at 50 mg/kg with sulfadiazine at 200 mg/kg, pyrimethamine at 12.5 mg/kg, clarithromycin at 200 mg/kg, or minocycline at 50 mg/kg. Efficacy was assessed by determination of survival rates and sequential determination of parasite burdens in blood, brain, and lungs. In vitro, atovaquone inhibited Toxoplasma growth at a concentration of > or = 0.02 mg/liter; the 50% inhibitory concentration was estimated to be 0.023 mg/liter. No synergistic effect was observed when it was combined with sulfadiazine, clarithromycin, or minocycline, whereas a significant antagonistic effect was noted for the combination of atovaquone with pyrimethamine. In vivo, administration of atovaquone at 100 or 50 mg/kg/day for 10 days resulted in prolonged survival compared with that in untreated mice; this survival was associated with a reduction of parasite burdens in blood and tissues during the course of treatment. The combinations of atovaquone with pyrimethamine, clarithromycin, or sulfadiazine were more efficient than each drug administered alone, in terms of survival, but parasite burdens in blood and organs were not reduced compared with those in mice treated with any of the agents alone. These experimental results confirmed the activity of atovaquone against Toxoplasma gondii, but no marked improvement in efficacy was observed in vitro and in vivo when this drug was combined with pyrimethamine, sulfadiazine, minocycline, or clarithromycin.

Animals↗
PubMed1993

In vitro susceptibilities of spotted fever group rickettsiae and Coxiella burnetti to clarithromycin.

The in vitro bacteriostatic activity of clarithromycin, a new macrolide derivative, against Rickettsia rickettsii, Rickettsia conorii, and "Rickettsia israeli" was determined by the plaque assay and the dye uptake assay. Both bacteriostatic and bactericidal activities of clarithromycin against the Nine Mile, Q212, Priscilla, and ME9 strains of Coxiella burnetti were evaluated by using three cell culture systems. Clarithromycin showed improved antibacterial activity compared with that of erythromycin. A bacteriostatic activity was obtained at concentrations below the reported maximum concentration of clarithromycin in human serum (about 4 micrograms/ml) for all tested rickettsiae. MICs ranged from 1 to 2 micrograms/ml for the three Rickettsia species and from 1 to 4 micrograms/ml for the C. burnetti strains. No bactericidal activity against C. burnetti was obtained when clarithromycin was used at 4 micrograms/ml.

Animals↗
PubMed1993

Efficacy of clarithromycin for treatment of experimental Lyme disease in vivo.

Clarithromycin provided effective therapy against arthritis induced by Borrelia burgdorferi infection in the hamster. In vitro, clarithromycin was at least 1 log more potent than tetracycline against two isolates of B. burgdorferi from human sources, as measured by MICs and 50% inhibitory concentrations. Clarithromycin was effective in preventing the onset of B. burgdorferi-induced arthritis, as determined by several parameters of paw swelling. When administered after the onset of arthritis, clarithromycin therapy reduced the degree of swelling and decreased recovery time. These results suggest that clarithromycin has potential as an effective therapy for Lyme disease.

Animals↗
PubMed1993

Clarithromycin, minocycline, and rifabutin treatments before and after infection of C57BL/6 mice with Mycobacterium avium.

C57BL/6 mice were pretreated with rifabutin or clarithromycin alone or combined with minocycline 3 days before intravenous challenge (day 0) with Mycobacterium avium. Treatment was continued until sacrifice at days 1, 8, 15, and 21. Rifabutin or clarithromycin decreased the level of infection in both the lungs and the spleen. Rifabutin was as effective as clarithromycin in the lungs but was less [corrected] effective in the spleen. The clarithromycin-minocycline combination was as effective as clarithromycin alone.

Animals↗
PubMed1993

Interaction between biofilms formed by Pseudomonas aeruginosa and clarithromycin.

Interactions between bacterial biofilms formed by Pseudomonas aeruginosa and clarithromycin, a macrolide having no anti-P. aeruginosa activity, were investigated. P. aeruginosa incubated for 10 days on membrane filters formed biofilms on the surfaces of the filters. The biofilms were characterized by dense colonizations of bacteria and thick membranous structures that covered the colonies. Treatment of the biofilms with a relatively low concentration of clarithromycin for 5 days resulted in an eradication of the membranous structures. Quantitative analysis of alginate and hexose was done to evaluate the quantity of polysaccharides in or on the biofilms. Treatment of the biofilms with clarithromycin decreased the quantity of alginate and hexose and therefore perhaps the quantity of polysaccharides as well. Eradication of the membranous structures of biofilms, or the decrease in the quantity of polysaccharides, resulted in an increase in the rate of penetration of antibiotics through bacterial biofilms. In vivo therapeutic effects of ofloxacin in the rat infection model, in which the biofilm mode of growth of P. aeruginosa is characteristic, were enhanced by oral coadministration of clarithromycin. It is suggested that clarithromycin eradicated glycocalyx produced by P. aeruginosa, or suppressed the production of glycocalyx, by unknown mechanisms and thereby enhanced the therapeutic efficacies of other antimicrobial agents against infections caused by P. aeruginosa.

Alginates↗
PubMed1994

Efficacies of liposome-encapsulated clarithromycin and ofloxacin against Mycobacterium avium-M. intracellulare complex in human macrophages.

The therapeutic efficacies of liposome-encapsulated ofloxacin and clarithromycin against Mycobacterium avium-M. intracellulare (MAI) were evaluated in a model of intramacrophage infection. Liposome encapsulation was found to markedly enhance the uptake of each of the drugs by human macrophages. The human blood-derived macrophages were infected at day 7 of culture with MAI. Treatment was initiated 24 h after the infection, and the number of intracellular bacteria was determined at days 2, 3, and 4. Liposome entrapment of either ofloxacin or clarithromycin significantly (P < 0.005) enhanced the activities of the drugs when compared with the antimycobacterial effects of equivalent concentrations of the free (unentrapped) drugs. The drugs were used at concentrations close to their clinically achievable peak levels. The efficacy of clarithromycin, either in the free or liposome-entrapped form, was markedly higher than that of ofloxacin. Liposome-encapsulated ofloxacin or clarithromycin plus ethambutol was, in each case, more effective in organism eradication (P < 0.005) than each agent used singly. These results suggest that liposome-encapsulated clarithromycin may be more effective than the free form of the drug against MAI infections in vivo, and the use of a combination therapy with ethambutol could further enhance the efficacy.

Clarithromycin↗
PubMed1994

Penetration of clarithromycin into lung tissues from patients undergoing lung resection.

The concentrations of clarithromycin and its active principal metabolite, 14-(R)-hydroxy-clarithromycin, were determined in lung tissue obtained during lung resection and compared with concomitant concentrations in plasma. Concentrations of the parent and metabolite were determined by high-performance liquid chromatography. The 15 patients studied were given 500 mg orally every 12 h for a minimum of five doses to achieve steady-state concentrations. The mean concentrations of clarithromycin and 14-(R)-hydroxy-clarithromycin in plasma just prior to the final dose were 1.38 and 0.67 micrograms/ml, respectively, and those 4 h after the final dose (at the time of lung resection) were 1.89 and 0.80 microgram/mL, respectively. The concentrations of the parent and metabolite in lung tissue at the time of lung resection averaged 54.3 and 5.12 micrograms/g, respectively, with a mean calculated ratio of concentrations of the parent to metabolite being 11.3 in lung tissue and 2.4 in plasma. Clarithromycin and its active metabolite are extensively distributed into human lung tissue.

Adolescent↗
PubMed1994

Tight binding of clarithromycin, its 14-(R)-hydroxy metabolite, and erythromycin to Helicobacter pylori ribosomes.

Clarithromycin is a recently approved macrolide with improved pharmacokinetics, antibacterial activity, and efficacy in treating bacterial infections including those caused by Helicobacter pylori, an agent implicated in various forms of gastric disease. We successfully isolated ribosomes from H. pylori and present the results of a study of their interaction with macrolides. Kinetic data were obtained by using 14C-labeled macrolides to probe the ribosomal binding site. Clarithromycin, its parent compound erythromycin, and its 14-(R)-hydroxy metabolite all bound tightly to H. pylori ribosomes. Kd values were in the range of 2 x 10(-10) M, which is the tightest binding interaction observed to date for a macrolide-ribosome complex. This tight binding was due to very slow dissociation rate constants of 7.07 x 10(-4), 6.83 x 10(-4), and 16.6 x 10(-4) min-1 for clarithromycin, erythromycin, and 14-hydroxyclarithromycin, respectively, giving half-times of dissociation ranging from 7 to 16 h, the slowest yet measured for a macrolide-ribosome complex. These dissociation rate constants are 2 orders of magnitude slower than the dissociation rate constants of macrolides from other gram-negative ribosomes. [14C]clarithromycin was bound stoichiometrically to 50S ribosomal subunits following incubation with 70S ribosomes and subsequent separation of the 30S and 50S subunits by sucrose density gradient centrifugation. These data predict that the lower MIC of clarithromycin compared with that of erythromycin for H. pylori is likely due to a faster rate of intracellular accumulation, possibly because of increased hydrophobicity.

Centrifugation, Density Gradient↗
PubMed1995

Treatment of Mycobacterium haemophilum infection in a murine model with clarithromycin, rifabutin, and ciprofloxacin.

An animal model of disseminated Mycobacterium haemophilum infection was utilized to compare treatment with azithromycin, ciprofloxacin, rifabutin, and the combination of clarithromycin with rifabutin. Following subcutaneous challenge with M. haemophilum, local and disseminated infection occurred only in immunosuppressed mice. For disseminated infection, ciprofloxacin was relatively ineffective therapy. Clarithromycin and rifabutin alone significantly reduced the tissue burden in the spleen after 4 weeks of therapy. Combination therapy with rifabutin and clarithromycin was superior to 4 weeks of treatment with the individual agents. When immunosuppressed mice were treated for 20 weeks with the combination of rifabutin and clarithromycin, the tissue burden remained reduced in the spleen at 1 month following the completion of therapy. Combined rifabutin and clarithromycin provide effective treatment for M. haemophilum in this model.

Animals↗
PubMed1995

Postantibiotic effect of clarithromycin alone and combined with ethambutol against Mycobacterium avium complex.

The postantibiotic effect (PAE) of clarithromycin alone and in combination with ethambutol was determined for two clinical blood isolates of Mycobacterium avium complex. An average PAE, ranging from 5.5 to 18.0 h, was noted for each isolate at each clarithromycin concentration except when isolate B was exposed to clarithromycin at the MIC. The addition of ethambutol did not enhance the PAE observed with clarithromycin alone. The clinical implications of the PAE of clarithromycin for M. avium complex remain to be determined.

AIDS-Related Opportunistic Infections↗
PubMed1996

Efficacy of clarithromycin treatment of acute otitis media caused by infection with penicillin-susceptible, -intermediate, and -resistant Streptococcus pneumoniae in the chinchilla.

Because of the increasing frequencies of recovery of penicillin-resistant Streptococcus pneumoniae from the middle ears of children with acute otitis media, non-beta-lactam antibiotics are being explored as treatment alternatives to amoxicillin. In this study, the efficacy of a 10-day course of clarithromycin was evaluated with chinchillas. After the pharmacokinetic profiles for clarithromycin were established, 180 animals were assigned to one of three susceptibility groups (n = 60/group; penicillin-susceptible, -intermediate, and -resistant S. pneumoniae), and the right middle ear was infected with the appropriate strain of S. pneumoniae. Equal numbers of animals in each group were treated orally beginning on day 2 with a 10-day course of clarithromycin (15 mg/kg of body weight; given twice a day) or amoxicillin as a control (20 mg/kg twice a day). On days 4, 9, and 13, otomicroscopy and tympanometry were performed, and on day 13, the middle ears were cultured for bacteria. The results showed 100% eradication of the challenge organism in both treatment groups for the susceptible strains of S. pneumoniae. Cultures were negative in 87 and 74% (P > 0.05) of the animals challenged with the intermediate resistant strains and in 100 and 56% (P < 0.05) of the animals challenged with the resistant strains and treated with clarithromycin and amoxicillin, respectively. There were no differences between treatments in the diagnosis of effusion for any group. These results support the use of the chinchilla to evaluate drug efficacy in the treatment of acute otitis media and show clarithromycin to be effective in sterilizing the middle ears of animals challenged with penicillin-susceptible, -intermediate, and -resistant strains of S. pneumoniae.

Amoxicillin↗
PubMed1997

Cloning and sequence analysis of two copies of a 23S rRNA gene from Helicobacter pylori and association of clarithromycin resistance with 23S rRNA mutations.

In this study, two identical copies of a 23S-5S gene cluster, which are separately situated within the Helicobacter pylori UA802 chromosome, were cloned and sequenced. Comparison of the DNA sequence of the H. pylori 23S rRNA gene with known sequences of other bacterial 23S rRNA genes indicated that the H. pylori UA802 23S rRNA genes are closely related to those of Campylobacter spp. and therefore belong in the proposed Proteobacteria subdivision. The 5'-terminal nucleotide T or A of the 23S rRNA is close to a Pribnow box which could be a -10 region of the transcription promoter for the 23S rRNA gene, suggesting that a posttranscriptional process is likely not involved in the maturation of the H. pylori 23S rRNA. Clinical isolates of H. pylori resistant to clarithromycin were examined by using natural transformation and pulsed-field gel electrophoresis. Cross-resistance to clarithromycin and erythromycin, which was transferred by natural transformation from the Cla(r) Ery(r) donor strain H. pylori E to the Cla(s) Ery(s) recipient strain H. pylori UA802, was associated with an single A-to-G transition mutation at position 2142 of both copies of the 23S rRNA in UA802 Cla(r) Ery(r) mutants. The transformation frequency for Cla(r) and Ery(r) was found to be approximately 2 x 10(-6) transformants per viable cell, and the MICs of both clarithromycin and erythromycin for the Cla(r) Ery(r) mutants were equal to those for the donor isolate. Our results confirmed the previous findings that mutations at positions 2142 and 2143 of the H. pylori 23S rRNA gene are responsible for clarithromycin resistance and suggest that acquisition of clarithromycin resistance in H. pylori could also result from horizontal transfer.

Anti-Bacterial Agents↗
PubMed1998

Oral cimetidine prolongs clarithromycin absorption.

The present study was conducted to identify any potential interaction between oral cimetidine and clarithromycin. Twelve healthy subjects were administered single doses of clarithromycin alone and with oral cimetidine dosed to steady state. Cimetidine prolonged the absorption of clarithromycin, as evidenced by decreased peak concentrations of both clarithromycin and 14-OH-clarithromycin (14OHC) in serum (46 and 43%, respectively), a delay in the formation of 14OHC (increase of 68%), and increases in both of their half-lives (75 and 82%, respectively), despite no changes in total oral clearance or area under the concentration-time curve for either compound. No mechanism for this interaction has been identified.

Absorption↗