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PubMed1999

Pharmacokinetics of azithromycin administered alone and with atovaquone in human immunodeficiency virus-infected children. The ACTG 254 Team.

To evaluate if atovaquone (ATQ) interacts pharmacokinetically with azithromycin (AZ) in human immunodeficiency virus-infected children, 10 subjects (ages, 4 to 13 years) were randomized in a crossover study to receive AZ (5 mg/kg/day) alone (ALONE) or AZ (5 mg/kg/day) and ATQ (30 mg/kg/day) simultaneously (SIM) prior to receiving AZ and ATQ staggered by 12 h. Despite a lack of significant difference in the mean AZ pharmacokinetic parameters, the steady-state values of AZ's area under the concentration-time curve from 0 to 24 h and maximum concentration in serum were consistently lower (n = 7 of 7) for the SIM regimen than they were for the ALONE regimen. A larger study will be required to determine if ATQ affects AZ pharmacokinetics and efficacy in a clinically significant manner.

Acquired Immunodeficiency Syndrome↗

PubMed1999

In vitro activities of azithromycin and ofloxacin against Chlamydia pneumoniae in a continuous-infection model.

Chlamydia pneumoniae is a well-established cause of community-acquired pneumonia and bronchitis in adults and children. Chronic infections with C. pneumoniae have been implicated in the development of atherosclerosis and other diseases in humans. Methods currently used for the culture and propagation of C. pneumoniae are not analogous to the infection as it occurs in vivo. We have established a model of continuous C. pneumoniae infection in vitro. HEp-2 cells inoculated with CM-1 and TW-183 strains have been persistently infected for periods of over 1.5 and 2 years, respectively. The cultures were maintained without centrifugation or the addition of cycloheximide, fresh host cells, or chlamydia. We observed cycles of host cell lysis, detachment, and regrowth with both strains of C. pneumoniae. Continuous C. pneumoniae infections may more closely resemble the actual events as they occur in vivo and, therefore, may be a better model for the in vitro study of C. pneumoniae infection. When we used continuously infected cells to determine the effects of azithromycin and ofloxacin on C. pneumoniae propagation in vitro, we found that both drugs reduced but did not completely eliminate the organism. This may be an important observation, as the failure of antibiotic therapy against C. pneumoniae infection in humans has been described.

Anti-Bacterial Agents↗

PubMed2000

Comparative pharmacodynamic analysis of Q-T interval prolongation induced by the macrolides clarithromycin, roxithromycin, and azithromycin in rats.

In order to evaluate the arrhythmogenic potency of macrolide antibiotics in a quantitative manner, we analyzed the influence of clarithromycin (CAM), roxithromycin (RXM), and azithromycin (AZM) on Q-T intervals from pharmacokinetic and pharmacodynamic points of view and in comparison with the potency of erythromycin (EM) previously reported by us for rats. Male Sprague-Dawley rats were anesthetized, and CAM (6.6, 21.6, and 43.2 mg/kg of body weight/h), RXM (20 and 40 mg/kg/h), and AZM (40 and 100 mg/kg/h) were intravenously injected for 90 min to obtain the time courses of drug concentrations in plasma and the changes in the Q-T intervals during and after the drug injections. Distinct Q-T interval prolongation of up to 10 ms was observed with CAM at its clinical concentrations. RXM and AZM evoked Q-T interval prolongation at concentrations higher than their clinical ranges. The potencies for Q-T interval prolongation, assessed as the slope of the concentration-response relationship, were 6.09, 0.536, and 0.989 ms. ml/microg for CAM, RXM, and AZM, respectively. There was hysteresis between the change in the Q-T intervals and the time course of the plasma concentration of each drug. The rank order of clinical arrhythmogenicity was estimated to be EM > CAM > RXM > AZM, as assessed from the present results and our previous report for EM. In conclusion, RXM and AZM were estimated to be less potent at provoking arrhythmia than EM and CAM. These results should be useful for making a safer choice of an appropriate agent for patients with electrocardiographic risk factors.

Algorithms↗

PubMed2001

Azithromycin inhibits quorum sensing in Pseudomonas aeruginosa.

We report that 2 microg of azithromycin/ml inhibits the quorum-sensing circuitry of Pseudomonas aeruginosa strain PAO1. Addition of synthetic autoinducers partially restored the expression of the trancriptional activator-encoding genes lasR and rhlR but not that of the autoinducer synthase-encoding gene lasI. We propose that azithromycin interferes with the synthesis of autoinducers, by an unknown mechanism, leading to a reduction of virulence factor production.

Anti-Bacterial Agents↗

PubMed2003

In vitro susceptibilities of Rhodococcus equi and other common equine pathogens to azithromycin, clarithromycin, and 20 other antimicrobials.

The objective of this study was to determine in vitro activities of azithromycin (AZM), clarithromycin (CLR), and 20 other antimicrobial agents against Rhodococcus equi and other common equine bacterial pathogens. A total of 201 bacterial isolates from various equine clinical samples were examined. CLR was more active than AZM against R. equi, with MICs at which 90% of the isolates were inhibited of 0.12 and 1.0 micro g/ml, respectively. Other antimicrobial agents highly active against at least 90% of R. equi isolates in vitro included rifampin, gentamicin, and imipenem. Both AZM and CLR showed good activity against beta-hemolytic streptococci and Staphylococcus spp. AZM was more active than other macrolides against Pasteurella spp. and Salmonella enterica.

Animals↗

PubMed2003

Randomized double-blind study comparing 3- and 6-day regimens of azithromycin with a 10-day amoxicillin-clavulanate regimen for treatment of acute bacterial sinusitis.

A randomized, double-blind, multicenter study of adults with acute bacterial sinusitis (ABS) compared the efficacy and safety of two azithromycin (AZM) regimens, 500 mg/day once daily for 3 days (AZM-3) or 6 days (AZM-6) to the efficacy and safety of an amoxicillin-clavulanate (AMC) regimen of 500-125 mg three times daily for 10 days. A total of 936 subjects with clinically and radiologically documented ABS were treated (AZM-3, 312; AZM-6, 311; AMC, 313). Clinical success rates were equivalent among per-protocol subjects at the end of therapy (AZM-3, 88.8%; AZM-6, 89.3%; AMC, 84.9%) and at the end of the study (AZM-3, 71.7%; AZM-6, 73.4%; AMC, 71.3%). Subjects treated with AMC reported a higher incidence of treatment-related adverse events (AE) (51.1%) than AZM-3 (31.1%, P < 0.001) or AZM-6 (37.6%, P < 0.001). More AMC subjects discontinued the study (n = 28) than AZM-3 (n = 7) and AZM-6 (n = 11) subjects. Diarrhea was the most frequent treatment-related AE. AZM-3 and AZM-6 were each equivalent in efficacy and better tolerated than AMC for ABS.

Acute Disease↗

PubMed2005

Impact of mass distribution of azithromycin on the antibiotic susceptibilities of ocular Chlamydia trachomatis.

In a community of Tanzania where trachoma is endemic, we cultured conjunctival swabs from all residents who had active trachoma and were PCR positive for ocular Chlamydia trachomatis, both before (43 isolates) and 2 months after (9 isolates) mass antibiotic treatment. No clinically or programmatically significant increase in azithromycin or tetracycline resistance was observed.

Azithromycin↗

PubMed2005

Cellular uptake and efflux of azithromycin, erythromycin, clarithromycin, telithromycin, and cethromycin.

Macrolide antibiotics have an outstanding ability to concentrate within host cells, particularly phagocytes. In the study described in this paper five different macrolide antibiotics were compared regarding the uptake and release kinetics in human peripheral blood polymorphonuclear neutrophils (PMNs) and three different cell lines, two phagocytic cell lines (RAW 264.7 and THP-1) and an epithelial cell line (MDCK). Based on the results obtained, the substances tested could be clustered into different groups. Azithromycin constituted the first group, characterized by rapid and nonsaturable uptake into phagocytic cells and a high degree of retention in the preloaded cells. The second group included erythromycin and clarithromycin. These two substances do not exhibit cell specificity; consequently, they are taken up to a similar extent and are released by all cell types studied. Ketolides constituted the last group. Their uptake was saturable in cells of monocytic lineage as well as in nondifferentiated cells of myeloid lineage, and they were rapidly released from all the cell lines studied. However, in PMNs, ketolide uptake was not saturable; and unlike telithromycin, cethromycin rapidly egressed from the loaded cells.

Animals↗

PubMed2005

Azithromycin inhibits the formation of flagellar filaments without suppressing flagellin synthesis in Salmonella enterica serovar typhimurium.

The present study shows that a sub-MIC of the macrolide antibiotic azithromycin (AZM) diminishes the virulence function of Salmonella enterica serovar Typhimurium. We first constructed an AZM-resistant strain (MS248) by introducing ermBC, an erythromycin ribosome methylase gene, into serovar Typhimurium. The MIC of AZM for MS248 exceeded 100 microg/ml. Second, we managed to determine the efficacy with which a sub-MIC of AZM reduced the virulence of MS248 in vitro. On the one hand, AZM (10 microg/ml) in the culture medium was unable to inhibit the total protein synthesis, growth rate, or survival within macrophages of MS248. On the other hand, AZM (10 microg/ml) reduced MS248's swarming and swimming motilities in addition to its invasive activity in Henle-407 cells. Electron micrographs revealed no flagellar filaments on the surface of MS248 after overnight growth in L broth supplemented with AZM (10 microg/ml). However, immunoblotting analysis showed that flagellin (FliC) was fully synthesized within the bacterial cells in the presence of AZM (10 microg/ml). In contrast, the same concentration of AZM reduced the export of FliC to the culture medium. These results indicate that a sub-MIC of AZM was able to affect the formation of flagellar filaments, specifically by reducing the amount of flagellin exported from bacterial cells, but it was not involved in suppressing the synthesis of flagellin. Unfortunately, AZM treatment was ineffective against murine salmonellosis caused by MS248.

Animals↗

PubMed2005

Molecular basis of azithromycin-resistant Pseudomonas aeruginosa biofilms.

Pseudomonas aeruginosa biofilms are extremely recalcitrant to antibiotic treatment. Treatment of cystic fibrosis patients with azithromycin (AZM) has shown promise. We used DNA microarrays to identify differentially expressed transcripts in developing P. aeruginosa biofilms exposed to 2 mug/ml AZM. We report that transcripts for multiple restriction-nodulation-cell division (RND) efflux pumps, known to be involved in planktonic antibiotic resistance, and transcripts involved in type III secretion were upregulated in the resistant biofilms that developed in the presence of AZM. Interestingly, the MexAB-OprM and MexCD-OprJ efflux pumps, but not type III secretion, appear to be integral to biofilm formation in the presence of AZM, as evidenced by the fact that a mutant deleted in both mexAB-oprM and mexCD-oprJ was unable to form a biofilm in the presence of AZM. A mutant deleted in type III secretion was still able to form biofilms in the presence of drug. Furthermore, single mexAB-oprM- and mexCD-oprJ-null mutants were able to form a biofilm in the presence of drug, indicating that either of the pumps can confer resistance to AZM during biofilm development. In contrast to planktonically grown cells, where no mexC expression was detectable regardless of the presence of AZM, biofilms exhibited induction of mexC expression from the outset of their formation, but only in the presence of AZM. mexA, which is constitutively expressed in planktonic cells, was uniformly expressed in biofilms regardless of the presence of AZM. These data indicate that the MexCD-OprJ pump acts as a biofilm-specific mechanism for AZM resistance.

Anti-Bacterial Agents↗

PubMed1995

Susceptibilities of 201 anaerobes to erythromycin, azithromycin, clarithromycin, and roxithromycin by oxyrase agar dilution and E test methodologies.

The susceptibility of 201 anaerobes to erythromycin, azithromycin, clarithromycin, and roxithromycin was tested by agar dilution and E test methods by using a commercially available plate and dish system (OxyDish) to provide anaerobic conditions. Plates were incubated for 48 h. MICs for 50% of strains tested and MICs for 90% of strains tested by agar dilution and E test methods corresponded within 1 doubling dilution for all compounds. When all antibiotics were considered together, agar and E test MICs were within 1 and 2 doubling dilutions of each other in 84 to 91% and > 99% of cases, respectively.

Agar↗

PubMed2004

Azithromycin retards Pseudomonas aeruginosa biofilm formation.

Using a flow cell biofilm model, we showed that a sub-MIC of azithromycin (AZM) can delay but not inhibit Pseudomonas aeruginosa biofilm formation and results in the development of a stable AZM resistance phenotype. Furthermore, mature biofilms were not affected by AZM.

Anti-Bacterial Agents↗

PubMed2003

Unusual presentation of early lymphogranuloma venereum in an HIV-1 infected patient: effective treatment with 1 g azithromycin.

The incidence of lymphogranuloma venereum (LGV) is low in the western world. Early LGV is characterised by bubonic disease following a painless papule or small ulcer. We report a white bisexual male who presented with a painful perianal ulcer, inguinal lymphadenitis, and concomitant infection with human immunodeficiency virus 1 (HIV-1). Chlamydia trachomatis serovar L2 was identified as the cause after polymerase chain reaction and genotyping the major outer membrane protein by restricted fragment length polymorphism. Treatment with a single dose of 1 g azithromycin was effective. This case illustrates that early LGV may mimic other genital ulcer diseases, such as genital herpes or chancroid, especially in HIV infected patients. In the western world, LGV must still be included in the differential diagnosis of bubonic disease with or without sexually acquired ulcers.

AIDS-Related Opportunistic Infections↗

PubMed2002

Effect of long term treatment with azithromycin on disease parameters in cystic fibrosis: a randomised trial.

BACKGROUND: Relentless chronic pulmonary inflammation is the major contributor to morbidity and mortality in patients with cystic fibrosis (CF). While immunomodulating therapies such as prednisolone and ibuprofen may be beneficial, their use is limited by side effects. Macrolides have immunomodulatory properties and long term use dramatically improves prognosis in diffuse panbronchiolitis, a condition with features in common with the lung disease of CF. METHODS: To determine if azithromycin (AZM) improves clinical parameters and reduces inflammation in patients with CF, a 3 month prospective randomised double blind, placebo controlled study of AZM (250 mg/day) was undertaken in adults with CF. Monthly assessment included lung function, weight, and quality of life (QOL). Blood and sputum collection assessed systemic inflammation and changes in bacterial flora. Respiratory exacerbations were treated according to the policy of the CF Unit. RESULTS: Sixty patients were recruited (29 men) of mean (SD) age 27.9 (6.5) years and initial forced expiratory volume in 1 second (FEV1) 56.6 (22.3)% predicted. FEV1% and forced vital capacity (FVC)% predicted were maintained in the AZM group while in the placebo group there was a mean (SE) decline of -3.62 (1.78)% (p=0.047) and -5.73 (1.66)% (p=0.001), respectively. Fewer courses of intravenous antibiotics were used in patients on AZM (0.37 v 1.13, p=0.016). Median C reactive protein (CRP) levels declined in the AZM group from 10 to 5.4 mg/ml but remained constant in the placebo group (p<0.001). QOL improved over time in patients on AZM and remained unchanged in those on placebo (p=0.035). CONCLUSION: AZM in adults with CF significantly improved QOL, reduced CRP levels and the number of respiratory exacerbations, and reduced the rate of decline in lung function. Long term AZM may have a significant impact on morbidity and mortality in patients with CF. Further studies are required to define frequency of dosing and duration of benefit.

Adolescent↗

PubMed2006

Moxifloxacin but not ciprofloxacin or azithromycin selectively inhibits IL-8, IL-6, ERK1/2, JNK, and NF-kappaB activation in a cystic fibrosis epithelial cell line.

Cystic fibrosis (CF) is associated with severe neutrophilic airway inflammation. We showed that moxifloxacin (MXF) inhibits IL-8 and MAPK activation in monocytic and respiratory epithelial cells. Azithromycin (AZM) and ciprofloxacin (CIP) are used clinically in CF. Thus we now examined effects of MXF, CIP, and AZM directly on CF cells. IB3, a CF bronchial cell line, and corrected C38 cells were treated with TNF-alpha, IL-1beta, or LPS with or without 5-50 microg/ml MXF, CIP, or AZM. IL-6 and IL-8 secretion (ELISA), MAPKs ERK1/2, JNK, p38, and p65 NF-kappaB (Western blot) activation were measured. Baseline IL-6 was sixfold higher in IB3 than C38 cells but IL-8 was similar. TNF-alpha and IL-1beta increased IL-6 and IL-8 12- to 67-fold with higher levels in IB3 than C38 cells post-TNF-alpha (P < 0.05). Levels were unchanged following LPS. Baseline phosphorylated form of ERK1/2 (p-ERK1/2), JNK, and NF-kappaB p65 were higher in IB3 than C38 cells (5-, 1.4-, and 1.4-fold), and following TNF-alpha increased, as did the p-p38, by 1.6- to 2-fold. MXF (5-50 microg/ml) and CIP (50 microg/ml), but not AZM, suppressed IL-6 and IL-8 secretion by up to 69%. MXF inhibited TNF-alpha-stimulated MAPKs ERK1/2, 46-kDa JNK, and NF-kappaB up to 60%, 40%, and 40%, respectively. In contrast, MXF did not inhibit p38 activation, implying a highly selective pretranslational effect. In conclusion, TNF-alpha and IL-1beta induce an exaggerated inflammatory response in CF airway cells, inhibited by MXF more than by CIP or AZM. Clinical trials are recommended to assess efficacy in CF and other chronic lung diseases.

Anti-Infective Agents↗

PubMed2004

Long term azithromycin therapy in cystic fibrosis patients: a study on drug levels and sputum properties.

BACKGROUND: Following reports on the treatment of diffuse panbronchiolitis (DPB), recent studies demonstrate that long term therapy with azithromycin (AZM) is effective in cystic fibrosis (CF) patients. However, the underlying mechanisms remain uncertain. Some macrolides, including AZM, display inhibition of virulence factors and other antipseudomonal effects at subinhibitory levels in vitro. OBJECTIVES: Drug doses used for CF and DPB therapy were investigated to determine whether they achieve corresponding sputum drug levels in CF patients in vivo. METHODS: In an open, prospective study, 14 CF patients with chronic Pseudomonas aeruginosa airway infection received 250 mg AZM either daily ('high dose') or twice weekly ('low dose') for 12 weeks. Viscoelasticity of sputum was assessed by magnetic microrheology. RESULTS: AZM accumulated in sputum by two orders of magnitude over a period of four weeks. In the following steady state, median AZM concentrations in sputum were 9.5 microg/mL (0.6 to 79.3 microg/mL, interquartiles 1.4 to 33.4 microg/mL) and 0.5 microg/mL (range less than 0.1 [below detection level] to 5.2 microg/mL, interquartiles 0.2 to 1.4 microg/mL) in the high and low dose groups, respectively. Viscoelasticity improved in all patients but one. CONCLUSIONS: The findings suggest that antipseudomonal activity has to be considered among the potential mechanisms of macrolide therapy. Further, viscoelasticity may be a valuable parameter in future clinical trials.

Adolescent↗

PubMedDate not supplied

In vitro comparative dynamics of modified-release clarithromycin and of azithromycin.

Antibacterial kinetics of modified-release clarithromycin (CLA) and azithromycin (AZI) against respiratory tract pathogens were compared in relation to their pharmacokinetic profile. The study was carried out in three strains of Streptococcus pneumoniae, group A beta-hemolytic Streptococcus pyogenes, Moraxella catarrhalis and Haemophilus influenzae, respectively, exposed to concentration gradients of CLA and AZI simulating human serum pharmacokinetics after administration of 500 mg p.o. in a single dose. Bactericidal kinetics were assessed by counting the number of survivors before each change in concentration over a period of 36 h. The minimal inhibitory concentrations (MICs) of CLA and AZI were evaluated at time 0 and after 36 h of exposure to antibiotics in the surviving organisms. The results showed that CLA and AZI, in the experimental conditions adopted, had different antibacterial kinetics. Moreover, the addition of the 14-OH metabolite of CLA at the same concentrations reached in human serum exerted a bactericidal effect against two strains of H. influenzae resistant to CLA and AZI. An increase in MICs was observed against S. pyogenes and H. influenzae, with higher values for AZI.

Anti-Bacterial Agents↗

PubMed1996

Inadequate azithromycin activity against Brucella melitensis in mice with acute or chronic infections.

The activities of therapeutic regimens with azithromycin (AZI) and doxycycline combined with streptomycin (DOX-SM) were compared in Brucella melitensis infected mice. In a chronic model, AZI given over 10, 14 or 21 consecutive days (50 mg/kg/24 h) significantly reduced the infection (1.3-1.6 logs, day 48 post-infection). However, the effectiveness of DOX (21 days, 50 mg/kg/12 h) was higher than AZI (3.4 logs of reduction, day 48 post-infection). Besides, when DOX was administered for 45 days, it "cured" all the animals from day 78. Similar results were obtained in an acute model infection. One single dose of DOX or DOX-SM, starting one day after lethal challenge, was able to protect 83% of the mice. In contrast, only 25% of the mice treated with AZI (50-200 mg/Kg) survived the challenge. Our findings demonstrate that AZI, in contrast to DOX-SM, does not cure experimental brucellosis.

Acute Disease↗