Susceptibilities of penicillin- and erythromycin-susceptible and -resistant pneumococci to HMR 3647 (RU 66647), a new ketolide, compared with susceptibilities to 17 other agents

Carbohydrate-based drugs launched during 2000-2021

Carbohydrates are fundamental molecules involved in nearly all aspects of lives, such as being involved in formating the genetic and energy materials, supporting the structure of organisms, constituting invasion and host defense systems, and forming antibiotics secondary metabolites. The naturally occurring carbohydrates and their derivatives have been extensively studied as therapeutic agents for the treatment of various diseases. During 2000 to 2021, totally 54 carbohydrate-based drugs which contain carbohydrate moities as the major structural units have been approved as drugs or diagnostic agents. Here we provide a comprehensive review on the chemical structures, activities, and clinical trial results of these carbohydrate-based drugs, which are categorized by their indications into antiviral drugs, antibacterial/antiparasitic drugs, anticancer drugs, antidiabetics drugs, cardiovascular drugs, nervous system drugs, and other agents.

Kinetics of drug-ribosome interactions defines the cidality of macrolide antibiotics

Antibiotics can cause dormancy (bacteriostasis) or induce death (cidality) of the targeted bacteria. The bactericidal capacity is one of the most important properties of antibacterial agents. However, the understanding of the fundamental differences in the mode of action of bacteriostatic or bactericidal antibiotics, especially those belonging to the same chemical class, is very rudimentary. Here, by examining the activity and binding properties of chemically distinct macrolide inhibitors of translation, we have identified a key difference in their interaction with the ribosome, which correlates with their ability to cause cell death. While bacteriostatic and bactericidal macrolides bind in the nascent peptide exit tunnel of the large ribosomal subunit with comparable affinities, the bactericidal antibiotics dissociate from the ribosome with significantly slower rates. The sluggish dissociation of bactericidal macrolides correlates with the presence in their structure of an extended alkyl-aryl side chain, which establishes idiosyncratic interactions with the ribosomal RNA. Mutations or chemical alterations of the rRNA nucleotides in the drug binding site can protect cells from macrolide-induced killing, even with inhibitor concentrations that significantly exceed those required for cell growth arrest. We propose that the increased translation downtime due to slow dissociation of the antibiotic may damage cells beyond the point where growth can be reinitiated upon the removal of the drug due to depletion of critical components of the gene-expression pathway.

Telithromycin

Telithromycin (Ketek), Aventis Pharma), a ketolide, belongs to a new class of antibiotics that was developed for the treatment of upper and lower respiratory tract infections. The prevalence of penicillin and macrolide resistance among respiratory pathogens is increasing in the USA. Telithromycin is highly active against beta-lactam, macrolide and fluoroquinolone reduced-susceptibility pathogens. Its efficacy has been shown to be equal or superior to comparator agents in numerous studies. It has a broad in vitro spectrum versus usual respiratory pathogens and oral once-daily dosing that increases patient compliance. Telithromycin penetrates rapidly into neutrophils in bronchopulmonary tissue, with peak levels obtained in 1 to 2 h. Results of clinical trials show clinical-esponse rates similar to comparator agents. The most frequent adverse events involve the gastrointestinal system, with mild to moderate diarrhea and nausea. A low rate of discontinuation was observed in the studies. Telithromycin is an effective first-line treatment for mild to moderate respiratory infections in adults.

Pharmacokinetics and Safety of the Ketolide Telithromycin in Patients with Renal Impairment

The pharmacokinetics and safety of the ketolide telithromycin were evaluated in two separate studies after single and repeat oral dosing in patients with varying degrees of renal impairment and in subjects with normal renal function. The single-dose study was an open-label, nonrandomized, parallel-group design in which all 40 patients received a single oral dose of telithromycin 800 mg. The repeat-dose study was an open-label study with a randomized, balanced, incomplete three-block treatment crossover design. In this study, each of the 36 patients received two of three telithromycin regimens (400, 600, or 800 mg once daily for 5 days), with a washout period of >/= 7 days between treatments. Telithromycin was well tolerated. Adverse events were generally mild in severity, and no serious drug-related adverse events were reported. Plasma exposure to telithromycin (C(max), AUC) showed a tendency to increase with increasing severity of renal impairment in both studies. In patients with severe renal impairment (CL(CR) < 30 mL/min) receiving telithromycin 800 mg in the repeat-dose study, C(max,ss) and AUC((0-24 h)ss) increased 1.5-fold (p < 0.05) to 2.0-fold (p = 0.0005), respectively, compared with healthy subjects. The percentage of dose excreted in urine and renal clearance (CL(R)) of telithromycin was found to decrease significantly with increasing severity of renal impairment in both studies, and CL(R) was found to be independent of telithromycin dose in the repeat-dose study. In conclusion, telithromycin dosage adjustment is not necessary in patients with mild to moderate renal impairment (CL(CR) >/= 30 mL/min). In patients with severe renal impairment (CL(CR) < 30 mL/min), dosage adjustment could be considered.

Antimicrobial-resistant Streptococcus pneumoniae: trends and management

Management of pneumococcal infections has been challenged by the development of resistance and, more recently, the unexpected spread of resistant clones of serotypes, such as 19A, following the introduction of a conjugate pneumococcal vaccine for use in children in 2000. High-dose penicillin G and many other agents continue to be efficacious parenterally for pneumonia and bacteremia. However, treatment options for meningitis and for infections treated with oral agents, particularly in children, have been limited by resistance. Empiric treatment guidelines should reflect the emerging threats from increased drug resistance. Compliance with guidelines by physicians and patients is important to prevent further development of resistance as new classes of agents are unlikely to be available in the next decade.

Antistreptococcal activity of AR-709 compared to that of other agents

Against 300 strains of pneumococci and 100 group A streptococci of differing beta-lactam, macrolide, and quinolone resistance phenotypes, AR-709 was very active, with all MICs being < or =2 microg/ml. Furthermore, AR-709 was active against strains that were both susceptible and resistant to trimethoprim-sulfamethoxazole.

Emergence of a Streptococcus pneumoniae isolate resistant to streptogramins by mutation in ribosomal protein L22 during pristinamycin therapy of pneumococcal pneumonia

OBJECTIVES

The aim of this study was to characterize the mechanism of resistance to macrolides and streptogramins of a Streptococcus pneumoniae strain isolated from blood cultures in an 80-year-old patient suffering from severe pneumonia unsuccessfully treated with pristinamycin.

METHODS

Resistance genes erm(B) and mef(A) were searched for by PCR. Portions of genes for domains V and II of the 23S rRNA (rrl) and genes for ribosomal proteins L4 (rplD) and L22 (rplV) were amplified by PCR from total genomic DNA and sequenced.

RESULTS

Resistance genes erm(B) and mef(A) were not detected. Only mutation in the rplV gene encoding ribosomal protein L22 was detected. The strain contained a six amino acid insertion ((107)KRTAHI(108)) in the C-terminus of the ribosomal protein L22.

CONCLUSIONS

This is the first report of emergence of a pneumococcus resistant to streptogramins by mutation in ribosomal protein L22 during treatment with pristinamycin.

[Antibiotherapy for acute CAP in adults]

Community acquired pneumonia is one of the most frequent infections. With time, bacterial epidemiology and bacterial resistance evolve and new antibiotics become available. So an up-date on adequate antibiotic use is necessary. We reviewed the epidemiology of pneumonia and the evolution of bacterial resistance. We also collected data on new antibiotics which can be used for this infection such as levofloxacin, moxifloxacin, telithromycin, and pristinamycin. All these drugs are effective on bacteria involved in pneumonia. At this time, only few Streptococcus pneumoniae strains have developed resistance to these drugs. However, resistance to fluoroquinolones is not easily detected with common laboratory techniques. There is no effectiveness difference between the 2 new fluoroquinolones (levofloxacin, moxifloxacin) in clinical studies. However, in bacteriological and pharmacological studies, moxifloxacin seems to be more effective than levofloxacin (500 mg/day). For the treatment of pneumonia due to Legionella pneumophila, fluoroquinolones are now widely recommended. For Streptococcus pneumonia, amoxicillin remain the drug of choice, even for bacteria with a decreased susceptibility to penicillin. The importance of treating atypical pathogens remains to be documented.

Acute bacterial rhinosinusitis: a review of U.S. treatment guidelines

Acute bacterial rhinosinusitis (ABRS) is a common complication of viral upper respiratory tract infections and is associated with a significant socioeconomic burden. Guidelines for the diagnosis and management of ABRS have been produced in association with a number of societies in the United States; these guidelines aim to promote the rational selection of antibiotic therapy to optimize clinical outcomes while minimizing the potential for selection of antibiotic resistance. This article provides an overview of current U.S. guidelines for the treatment of ABRS, focusing on the impact of antibiotic resistance on treatment options.

Pharmacokinetics of telithromycin using bronchoscopic microsampling after single and multiple oral doses

OBJECTIVES

Bronchoscopic microsampling (BMS) is a new technique for repeated sampling of bronchial epithelial lining fluid (ELF) to obtain the pharmacokinetic profile of drugs. We analyzed the time versus concentration profiles of telithromycin in bronchial ELF obtained by BMS and compared these finding to those in plasma and alveolar ELF obtained by bronchoalveolar lavage (BAL).

METHODS

Bronchial ELF samples were obtained from five healthy subjects using BMS probe at 0, 2, 3, 4, 6, 10 and 24h after single or multiple oral doses of 600 mg of telithromycin. Alveolar ELF was also obtained by BAL 3h after single or multiple oral doses of 600 mg of telithromycin.

RESULTS

The areas under the concentration-time curve from 0 to 24h (AUC0-24) of telithromycin in plasma and bronchial ELF were 2.86+/-0.60 and 19.5+/-10.4 mg h/l after single treatment and 3.60+/-0.49 and 42.2+/-22.7 mg h/l after multiple treatments, respectively. Single and multiple oral doses of telithromycin produced significantly (p<0.05) higher AUC0-24 in bronchial ELF compared to those in plasma. While concentrations in bronchial ELF obtained by BMS were significantly lower than those in alveolar ELF obtained by BAL, they tended to be higher than those in plasma after multiple administration. The telithromycin concentrations obtained by BMS method were very consistent in bronchial ELF at different bronchi at one time point and at the same bronchus at different time points.

CONCLUSIONS

Using the BMS technique, we could describe the pharmacokinetics of telithromycin in bronchial ELF. Furthermore, BMS was reasonably validated and reconfirmed to be a feasible and reliable method for measuring antimicrobial concentrations in bronchial ELF.

Managing acute lower respiratory tract infections in an era of antibacterial resistance

Respiratory tract infections account for more than 116 million office visits and an estimated 3 million visits to hospital EDs annually. Patients presenting at EDs with symptoms suggestive of lower respiratory tract infections of suspected bacterial etiology are often severely ill, thus requiring a rapid presumptive diagnosis and empiric antimicrobial treatment. Traditionally, clinicians have relied on beta-lactam or macrolide antibiotics to manage community-acquired lower respiratory tract infections. However, the emerging resistance of Streptococcus pneumoniae to beta-lactams and/or macrolides may affect the clinical efficacy of these agents. Inappropriate use of antibiotics and use of agents with an overly broad spectrum of antimicrobial activity have contributed to the emergence of antibiotic resistance. When treating respiratory infections, clinicians need to prescribe antimicrobial agents only for those individuals with infections of suspected bacterial etiology; to select agents with a targeted spectrum of activity that ensures coverage against typical S pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis strains, including antibiotic-resistant strains and atypical pathogens; and to consider agents with specific chemical properties that limit the development of antimicrobial resistance and that achieve concentrations at sites of infection that exceed those required for bactericidal activity. Newer classes of antimicrobial agents, such as the oxazolidinones and ketolides, will likely play a significant role in this era of antimicrobial resistance.

Telithromycin in the treatment of acute bacterial sinusitis, acute exacerbations of chronic bronchitis, and community-acquired pneumonia

Acute bacterial sinusitis (ABS), acute exacerbations of chronic bronchitis (AECB), and community-acquired pneumonia (CAP) are common conditions and constitute a substantial socioeconomic burden. The ketolides are a new class of antibacterials with a targeted spectrum of antibacterial activity. In vitro, telithromycin is active against common bacterial pathogens that cause upper and lower respiratory tract infections, including some isolates that are resistant to other antibiotic classes. In 2004, telithromycin was the first ketolide antibiotic approved for clinical use by the US Food and Drug Administration for the treatment of adult outpatients with ABS, AECB, and mild-to-moderate CAP. This review discusses the use of telithromycin in the treatment of these infections, providing an overview of its antibacterial activity, pharmacokinetic and pharmacodynamic properties, clinical efficacy, and tolerability-safety, and concludes that telithromycin is an appropriate option for the treatment of community-acquired ABS, AECB, and mild-to-moderate CAP.

[Efficacy and safety of telithromycin in the treatment of acute exacerbation of chronic obstructive pulmonary disease]

The aim of this study was to evaluate the clinical efficacy of telithromycin administered for 5 days at a dosage of 800 mg/day, in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) presenting with at least 2 of Anthonisen's criteria including the increase of purulence.

METHODOLOGY

During this multicenter (211 private lung specialists), prospective, non-comparative, open-labeled French study, 365 patients were included between April 2002 and March 2003. Clinical efficacy was assessed on D12-D19 by the rate of clinical success as defined by recovery or clinical improvement (main endpoint) according to the number of exacerbation episodes during the previous year.

RESULTS

On D12-D19 clinical success rate in the per protocol global population was 88.0% and respectively 87.9% in patients with <or=3 episodes in the previous year and 88.6% in patients with >or=4 episodes in the previous year. These success rates were similar to those in the intent-to-treat population. Safety, assessed on 359 patients, was satisfactory, with mainly digestive disorders related to the treatment in 3.9% of the patients. No treatment-related serious adverse events were observed.

CONCLUSION

This study, conducted among private practitioners in France according to COPD classification as defined by official recommendations, validates the results obtained in previous studies. Our results confirm the place attributed to telithromycin in the treatment of patients presenting with AECOPD without chronic respiratory failure, according to ongoing official recommendations.

Five-Day Telithromycin Once Daily Is as Effective as 10-Day Clarithromycin Twice Daily for the Treatment of Acute Exacerbations of Chronic Bronchitis and Is Associated With Reduced Health-Care Resource Utilization

STUDY OBJECTIVES

To demonstrate equivalence in the clinical efficacy of telithromycin vs clarithromycin treatment of outpatients with acute exacerbations of chronic bronchitis (AECB), and to compare the tolerability and respiratory-related health-care resource utilization associated with these treatment regimens.

DESIGN AND PATIENTS

A randomized, double-blind, multicenter, clinical study was conducted at 105 centers in 14 countries. Adult outpatients (age > or = 30 years) received oral telithromycin, 800 mg qd for 5 days (n = 270), or oral clarithromycin, 500 mg bid for 10 days (n = 282), for the treatment of AECB. Clinical and bacteriologic outcomes were assessed at the posttherapy/test-of-cure (TOC) visit (days 17 to 24; per-protocol population). Health-care resource utilization data were collected for each patient by investigators blinded to study medication up to the late posttherapy visit (days 31 to 36).

RESULTS

Clinical cure rates at the posttherapy/TOC visit were comparable between the groups (telithromycin, 193 of 225 patients [85.8%]; clarithromycin, 206 of 231 patients [89.2%]); bacteriologic outcome was satisfactory for 59 of 72 telithromycin-treated patients (81.9%) vs 63 of 76 clarithromycin-treated patients (82.9%). Health-care resource utilization assessed up to the late posttherapy visit was lower in the telithromycin treatment group than the clarithromycin treatment group, with significantly fewer hospitalizations for respiratory-related causes (one hospitalization vs eight hospitalizations for a total of 4 inpatient days vs 39 inpatient days, respectively), significantly fewer AECB-related emergency department visits (0 vs 8), and fewer unscheduled outpatient visits (11 vs 18). Fewer telithromycin-treated patients reported days lost from work (21 of 91 patients [23.1%]; 133 days) compared with those receiving clarithromycin (30 of 98 patients [30.6%]; 141 days). Telithromycin was well tolerated; adverse events considered possibly related to study medication were reported by 61 of 269 patients (22.7%) and 100 of 280 patients (35.7%) receiving telithromycin and clarithromycin, respectively.

CONCLUSIONS

In this study, 5-day telithromycin treatment was as effective and well tolerated as 10-day clarithromycin treatment for patients with AECB, and was associated with a reduced utilization of health-care resources.

Evaluation of telithromycin against Streptococcus pneumoniae with ribosomal mutations utilizing in vitro time-kill methodology

In a recent study, our in vivo data suggested that clinically achievable levels of telithromycin are more effective than azithromycin against selected Streptococcus pneumoniae isolates with ribosomal mutations in 23S rRNA gene alleles and L22 region mutations. In the current study, we attempt to investigate further the antibacterial activity of telithromycin against these isolates to better delineate the disparity between isolates based on allelic differences. Four isolates of S. pneumoniae with ribosomal mutations were tested using in vitro time-kill methodology. Isolates were exposed to telithromycin at concentrations of 0.5-8 x the minimum inhibitory concentration (MIC). At these exposures, telithromycin demonstrated concentration-dependent killing for three of the four isolates. Against the fourth isolate, telithromycin affected only a 1 log decrease in colony-forming units/mL despite exposures of 8 x MIC. These data demonstrate the in vitro killing profile of telithromycin against S. pneumoniae isolates with ribosomal and L22 mutations. Whilst telithromycin did not demonstrate bactericidal activity against all isolates in these time-kill studies, the in vivo human-simulated exposures did result in a high degree of bacterial kill. Full evaluation of the potential utility of new antimicrobial agents against these emerging genotypic profiles requires both in vitro and in vivo assessments.

Bacteriological efficacy of 5-day therapy with telithromycin in acute maxillary sinusitis

Increasing resistance among the key pathogens responsible for community-acquired respiratory tract infections, namely Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, has the potential to limit the effectiveness of the antibacterial agents available to treat these infections. Moreover, there are regional differences in the susceptibility patterns observed and, as treatment is usually empirical, choosing an effective treatment can be challenging. Telithromycin, the first ketolide to be approved for clinical use, offers an activity profile that covers the key respiratory pathogens including penicillin- and macrolide-resistant S. pneumoniae as well as beta-lactamase-producing H. influenzae and M. catarrhalis. In a pooled analysis of three large controlled clinical trials involving patients with acute maxillary sinusitis, the bacteriological efficacy of 5- or 10-day treatment with telithromycin and 10-day treatment with comparators was evaluated. Telithromycin administered as a once-daily 800 mg dose for 5 days achieved eradication rates of 91.8, 87.5 and 92.9% for S. pneumoniae, H. influenzae and M. catarrhalis, respectively. Bacteriological eradication of 8/10 and 12/14 isolates of S. pneumoniae resistant to penicillin and erythromycin, respectively, was also reported following 5-day treatment with telithromycin. The clinical efficacy of this regimen was equivalent to that of a 10-day regimen of telithromycin or standard 10-day courses of amoxicillin-clavulanic acid or cefuroxime axetil. Telithromycin 800mg given for 5 days was well tolerated, with the majority of adverse events being of mild or moderate intensity. These data suggest that telithromycin provides effective first-line therapy for use in patients with acute maxillary sinusitis in a short and convenient once-daily dosage regimen.

Antipneumococcal activity of ceftobiprole, a novel broad-spectrum cephalosporin

Ceftobiprole (previously known as BAL9141), an anti-methicillin-resistant Staphylococcus aureus cephalosporin, was very highly active against a panel of 299 drug-susceptible and -resistant pneumococci, with MIC(50) and MIC(90) values (microg/ml) of 0.016 and 0.016 (penicillin susceptible), 0.06 and 0.5 (penicillin intermediate), and 0.5 and 1.0 (penicillin resistant). Ceftobiprole, imipenem, and ertapenem had lower MICs against all pneumococcal strains than amoxicillin, cefepime, ceftriaxone, cefotaxime, cefuroxime, or cefdinir. Macrolide and penicillin G MICs generally varied in parallel, whereas fluoroquinolone MICs did not correlate with penicillin or macrolide susceptibility or resistance. All strains were susceptible to linezolid, quinupristin-dalfopristin, daptomycin, vancomycin, and teicoplanin. Time-kill analyses showed that at 1x and 2x the MIC, ceftobiprole was bactericidal against 10/12 and 11/12 strains, respectively. Levofloxacin, moxifloxacin, vancomycin, and teicoplanin were each bactericidal against 10 to 12 strains at 2x the MIC. Azithromycin and clarithromycin were slowly bactericidal, and telithromycin was bactericidal against only 5/12 strains at 2x the MIC. Linezolid was mainly bacteriostatic, whereas quinupristin-dalfopristin and daptomycin showed marked killing at early time periods. Prolonged serial passage in the presence of subinhibitory concentrations of ceftobiprole failed to yield mutants with high MICs towards this cephalosporin, and single-passage selection showed very low frequencies of spontaneous mutants with breakthrough MICs towards ceftobiprole.

Telithromycin: A Ketolide Antibiotic for Treatment of Respiratory Tract Infections

Telithromycin, a recently approved ketolide antibiotic derived from 14-membered macrolides, is active against erythromycin-resistant pneumococci. Telithromycin has enhanced activity in vitro because it binds not only to domain V of ribosomal RNA (like macrolides do) but also to domain II. However, it is not active against streptococci and staphylococci with constitutive macrolide, lincosamide, and streptogramin B resistance. Telithromycin, available in an oral formulation, is approved by the US Food and Drug Administration for use in adults for treatment of (1) community-acquired pneumonia due to Streptococcus pneumoniae (including multidrug-resistant isolates), Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae, or Mycoplasma pneumoniae; (2) acute exacerbation of chronic bronchitis due to S. pneumoniae, H. influenzae, or M. catarrhalis; or (3) acute bacterial sinusitis due to S. pneumoniae, H. influenzae, M. catarrhalis, or methicillin- and erythromycin-susceptible Streptococcus aureus. It is not approved for treatment of tonsillitis, pharyngitis, or severe pneumococcal pneumonia. Unique visual adverse effects occurred in 0.27%-2.1% of patients receiving telithromycin therapy. Its enhanced activity against some common respiratory pathogens makes it a valuable addition to the available macrolides.

Telithromycin for the treatment of acute exacerbations of chronic bronchitis

Pooled data from three randomized, double-blind, multi- centre studies evaluated the efficacy and tolerability of telithromycin 800 mg once daily for 5 days vs. standard comparators (10-day amoxicillin-clavulanate 500/125 mg three times daily, clarithromycin 500 mg or cefuroxime axetil 500 mg twice daily) in the outpatient treatment for acute exacerbations of chronic bronchitis. Per-protocol clinical cure rates at post-therapy/test of cure (days 17-24) were 86.0 and 85.8% for telithromycin and comparators, respectively, and 79.1 and 78.7%, respectively, at late post-therapy (days 31-36). Clinical cure rates were comparable for patients at increased risk, including those of > or =65 years and those with severe infection or significant airway obstruction (telithromycin, > or =77.1%; comparators, > or =75.0%). Telithromycin was well tolerated. Most adverse events considered possibly related to study medication were gastrointestinal and of mild intensity. In conclusion, 5-day telithromycin therapy is as effective and well tolerated as 10-day treatment with standard comparators.

Pharmacodynamic profile of telithromycin against macrolide- and fluoroquinolone-resistant Streptococcus pneumoniae in a neutropenic mouse thigh model

The new ketolide telithromycin has potent in vitro activity against Streptococcus pneumoniae, including strains resistant to penicillin, macrolides, and fluoroquinolones. The aim of the present study was to define the pharmacodynamic profile of telithromycin against S. pneumoniae strains with various resistance profiles in an in vivo system. Ten S. pneumoniae strains were studied; seven exhibited penicillin resistance, six demonstrated macrolide resistance, and two exhibited gatifloxacin resistance. The telithromycin MICs for all isolates were < or =0.5 microg/ml. Using the murine thigh infection model, CD-1/ICR mice were rendered neutropenic and were then inoculated with 10(5) to 10(6) CFU of S. pneumoniae per thigh. Telithromycin was administered orally at doses ranging from 25 to 800 mg/kg of body weight/day, with the doses administered one, two, three, or four times a day. The activity of telithromycin was assessed by determination of the change in the bacterial density in thigh tissue after 24 h of treatment for each treatment group and the untreated controls. Pharmacokinetic studies of telithromycin were conducted in infected, neutropenic animals. The levels of protein binding by telithromycin in mice ranged from 70 to 95% over the observed range of pharmacokinetic concentrations. By using either the total or the free concentrations of telithromycin, the area under the concentration-time curve (AUC)/MIC ratio was a strong determinant of the response against S. pneumoniae, regardless of the phenotypic resistance profile. The maximal efficacy (the 95% effective dose) against this cohort of S. pneumoniae strains and bacterial inhibition (stasis) of telithromycin were predicted by ratios of the AUC for the free drug concentration/MIC of approximately 1,000 and 200, respectively.

In vitro activities of novel 2-fluoro-naphthyridine-containing ketolides

In vitro activities of erythromycin A, telithromycin, and two investigational ketolides, JNJ-17155437 and JNJ-17155528, were evaluated against clinical bacterial strains, including selected common respiratory tract pathogens. Against 46 macrolide-susceptible and -resistant Streptococcus pneumoniae strains, the MIC(90) (MIC at which 90% of the isolates tested were inhibited) of the investigational ketolides was 0.25 microg/ml, twofold lower than that of telithromycin and at least 64-fold lower than that of erythromycin A. Against erm(B)-containing pneumococci, the MIC(90) of all the ketolides was 0.06 microg/ml. The MIC(90) of the investigational ketolides against mef(A)-containing pneumococci or pneumococci with both mef(A) and erm(B) was 0.25 microg/ml, two-and fourfold lower, respectively, than that of telithromycin. In contrast, the MICs of the investigational ketolides against macrolide-resistant S. pneumoniae strains with ribosomal mutations were similar to or, in some cases, as much as eightfold higher than those of telithromycin. Against Haemophilus influenzae, MICs of all the ketolides were < or =2 microg/ml. Against three Moraxella catarrhalis isolates, the MIC of the ketolides was 0.25 microg/ml. The ketolides inhibited in vitro protein synthesis, with 50% inhibitory concentrations ranging from 0.23 to 0.27 microM. In time-kill studies against macrolide-susceptible and erm- or mef-containing pneumococci, the ketolides were bacteriostatic to slowly bactericidal, with 24-h log(10) decreases ranging from 2.0 to 4.1 CFU. Intervals of postantibiotic effects for the ketolides against macrolide-susceptible and -resistant S. pneumoniae were 3.0 to 8.1 h.

Update on treatment guidelines for acute bacterial sinusitis

Acute bacterial sinusitis (ABS) is a common complication of viral upper respiratory tract infections and represents a considerable social burden both in terms of diminished quality of life for the patient and the economic implications of decreased productivity and treatment costs. Several national health authorities have developed guidelines for the management of ABS, which aim to promote rational selection of anti-bacterial therapy to optimise clinical outcomes while minimising the potential for selection of anti-bacterial resistance as a result of inappropriate anti-bacterial usage. This article provides an overview of current guidelines, with particular focus on the clinical significance of variations in treatment recommendations and new treatment options, such as the ketolide telithromycin, which was recently added to a number of national treatment guidelines.

Antipneumococcal activities of two novel macrolides, GW 773546 and GW 708408, compared with those of erythromycin, azithromycin, clarithromycin, clindamycin, and telithromycin

The MICs of GW 773546, GW 708408, and telithromycin for 164 macrolide-susceptible and 161 macrolide-resistant pneumococci were low. The MICs of GW 773546, GW 708408, and telithromycin for macrolide-resistant strains were similar, irrespective of the resistance genotypes of the strains. Clindamycin was active against all macrolide-resistant strains except those with erm(B) and one strain with a 23S rRNA mutation. GW 773546, GW 708408, and telithromycin at two times their MICs were bactericidal after 24 h for 7 to 8 of 12 strains. Serial passages of 12 strains in the presence of sub-MICs yielded 54 mutants, 29 of which had changes in the L4 or L22 protein or the 23S rRNA sequence. Among the macrolide-susceptible strains, resistant mutants developed most rapidly after passage in the presence of clindamycin, GW 773546, erythromycin, azithromycin, and clarithromycin and slowest after passage in the presence of GW 708408 and telithromycin. Selection of strains for which MICs were >/=0.5 microg/ml from susceptible parents occurred only with erythromycin, azithromycin, clarithromycin, and clindamycin; 36 resistant clones from susceptible parent strains had changes in the sequences of the L4 or L22 protein or 23S rRNA. No mef(E) strains yielded resistant clones after passage in the presence of erythromycin and azithromycin. Selection with GW 773546, GW 708408, telithromycin, and clindamycin in two mef(E) strains did not raise the erythromycin, azithromycin, and clarithromycin MICs more than twofold. There were no change in the ribosomal protein (L4 or L22) or 23S rRNA sequences for 15 of 18 mutants selected for macrolide resistance; 3 mutants had changes in the L22-protein sequence. GW 773546, GW 708408, and telithromycin selected clones for which MICs were 0.03 to >2.0 microg/ml. Single-step studies showed mutation frequencies <5.0 x 10(-10) to 3.5 x 10(-7) for GW 773546, GW 708408, and telithromycin for macrolide-susceptible strains and 1.1 x 10(-7) to >4.3 x 10(-3) for resistant strains. The postantibiotic effects of GW 773546, GW 708408, and telithromycin were 2.4 to 9.8 h.

Macrolides and ketolides: azithromycin, clarithromycin, telithromycin

The advanced macrolides, azithromycin and clarithromycin, and the ketolide telithromycin are structural analogues of erythromycin. They have several distinct advantages when compared with erythromycin including enhanced spectrum of activity, more favorable pharmacokinetics and pharmacodynamics, once daily administration, and improved tolerability. This article reviews the pharmacokinetics, antimicrobial activity, clinical use, and adverse effects of these antimicrobial agents.

Activity of telithromycin against erythromycin-susceptible and -resistant Streptococcus pneumoniae isolates from adults with invasive infections

A telithromycin (TEL) kill-kinetics study was conducted with 120 clinically significant Streptococcus pneumoniae isolates (60 susceptible and 60 highly resistant to erythromycin). Time-kill curves were performed using different antibiotic concentrations. The minimum inhibitory concentrations (MICs) of TEL were low for both erythromycin-susceptible (MIC < or = 0.016 mg/L) and erythromycin-resistant strains (MIC < or = 0.25 mg/L). TEL showed 99.9% killing of all erythromycin resistant strains at 18-24 h of incubation. Even for strains with erythromycin MICs > or = 64.0 mg/L, TEL was uniformly bactericidal at 0.25 mg/L.

Ketolide antimicrobial activity persists after disruption of interactions with domain II of 23S rRNA

Ketolides are the latest derivatives developed from the macrolide erythromycin to improve antimicrobial activity. All macrolides and ketolides bind to the 50S ribosomal subunit, where they come into contact with adenosine 2058 (A2058) within domain V of the 23S rRNA and block protein synthesis. An additional interaction at nucleotide A752 in the rRNA domain II is made via the synthetic carbamate-alkyl-aryl substituent in the ketolides HMR3647 (telithromycin) and HMR3004, and this interaction contributes to their improved activities. Only a few macrolides, including tylosin, come into contact with domain II of the rRNA and do so via interactions with nucleotides G748 and A752. We have disrupted these macrolide-ketolide interaction sites in the rRNA to assess their relative importance for binding. Base substitutions at A752 were shown to confer low levels of resistance to telithromycin but not to HMR3004, while deletion of A752 confers low levels of resistance to both ketolides. Mutations at position 748 confer no resistance. Substitution of guanine at A2058 gives rise to the MLS(B) (macrolide, lincosamide, and streptogramin B) phenotype, which confers resistance to all the drugs. However, resistance to ketolides was abolished when the mutation at position 2058 was combined with a mutation in domain II of the same rRNA. In contrast, the same dual mutations in rRNAs conferred enhanced resistance to tylosin. Our results show that the domain II interactions of telithromycin and HMR3004 differ from each other and from those of tylosin. The data provide no indication that mutations within domain II, either alone or in combination with an A2058 mutation, can confer significant levels of telithromycin resistance.

Ketolides: an emerging treatment for macrolide-resistant respiratory infections, focusing on S. pneumoniae

Resistance to antibiotics in community acquired respiratory infections is increasing worldwide. Resistance to the macrolides can be class-specific, as in efflux or ribosomal mutations, or, in the case of erythromycin ribosomal methylase (erm)-mediated resistance, may generate cross-resistance to other related classes. The ketolides are a new subclass of macrolides specifically designed to combat macrolide-resistant respiratory pathogens. X-ray crystallography indicates that ketolides bind to a secondary region in domain II of the 23S rRNA subunit, resulting in an improved structure-activity relationship. Telithromycin and cethromycin (formerly ABT-773) are the two most clinically advanced ketolides, exhibiting greater activity towards both typical and atypical respiratory pathogens. As a subclass of macrolides, ketolides demonstrate potent activity against most macrolide-resistant streptococci, including ermB- and macrolide efflux (mef)A-positive Streptococcus pneumoniae. Their pharmacokinetics display a long half-life as well as extensive tissue distribution and uptake into respiratory tissues and fluids, allowing for once-daily dosing. Clinical trials focusing on respiratory infections indicate bacteriological and clinical cure rates similar to comparators, even in patients infected with macrolide-resistant strains.

Efficacy and safety of oral telithromycin once daily for 5 days versus moxifloxacin once daily for 10 days in the treatment of acute bacterial rhinosinusitis

OBJECTIVE

To compare the clinical and bacteriologic efficacy and safety of short-duration treatment with telithromycin given for 5 days with moxifloxacin given for 10 days in adults with acute bacterial rhinosinusitis (ABRS).

STUDY DESIGN

In this prospective, double-blind, parallel-group, randomized, multicenter study, adult patients (N = 349) with ABRS were randomized to oral telithromycin (800 mg once daily for 5 days) or to oral moxifloxacin (400 mg once daily for 10 days) and followed for 31 to 36 days. Clinical outcome was determined by the investigator at the posttherapy/test of cure (TOC) visit. Bacteriologic outcome was determined by comparing cultures taken at the pretreatment visit with cultures obtained at the posttherapy/TOC visit. The primary objective was to demonstrate equivalence of clinical cure rates in the per-protocol population between treatment groups at the posttherapy/TOC visit.

RESULTS

Clinical success at TOC (primary endpoint) was achieved in 87.4% of patients in the telithromycin group compared with 86.9% for moxifloxacin (per-protocol patients; 0.5% difference between treatment groups; 95% confidence interval [CI], -8.1, 9.2; P = 0.8930). The bacteriologic success rates were 94.1% and 93.9%, respectively (0.2% difference between treatment groups; 95% CI, -14.2, 14.5; P = 0.9734). Overall treatment-emergent adverse events for both drugs (mostly gastrointestinal) were mild to moderate in intensity.

CONCLUSION AND SIGNIFICANCE

The clinical and bacteriologic efficacy of telithromycin 800 mg once daily for 5 days was equivalent to that of moxifloxacin 400 mg once daily for 10 days, establishing telithromycin as an important treatment option for ABRS.

Streptococcus pneumoniae: epidemiology and patterns of resistance

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, otitis media, and sinusitis; it results in significant morbidity and mortality in patients with pneumonia and meningitis. The pneumococcus is a common colonizing bacterium in the respiratory tract; it is especially common in the respiratory tracts of children, where it is frequently exposed to antimicrobial agents. This exposure can lead to resistance. Penicillin nonsusceptibility is found in nearly 40% of strains causing disease in adults, although often these cases are treatable with appropriate dosing regimens of many oral and parenteral beta-lactam agents. In the United States resistance to macrolides is widespread--averaging approximately 28%--but geographically variable, ranging from 23% in the northwest to 30% in the northeast. Resistance to tetracyclines and trimethoprim-sulfamethoxazole are reported in approximately 20% and 35% of isolates, respectively, and resistance to multiple classes of agents is increasingly common. Amoxicillin, amoxicillin-clavulanate, respiratory fluoroquinolones, and clindamycin are currently the most effective agents for treatment of respiratory tract infections caused by S pneumoniae, with >90% of isolates in the United States being susceptible. Vancomycin is the only agent against which resistance has not emerged. Patient groups that are at increased risk for developing resistant pneumococcal infections have been identified and include patients with malignancies, human immunodeficiency virus infection, and sickle-cell disease. Judicious use of antimicrobials is the key to preventing the emergence of further resistance, particularly as few new classes of agents are likely to become available for clinical use in the short term.

Comparative in vitro activity of antiribosomal agents on penicillin-susceptible and -resistant Streptococcus pneumoniae in relation to their resistance genotypes

A collection of 326 strains of Streptococcus pneumoniae isolated from blood, cerebrospinal fluid, bronchoalveolar lavage, transtracheal aspirate or sputum from January 1996-June 2002 were included in this study. The activity of clarithromycin, clindamycin, telithromycin, linezolid and quinupristin/dalfopristin against penicillin G and erythromycin A susceptible and resistant pneumococci were determined; the erythromycin A resistance phenotypes and genotypes were identified and susceptibilities of these agents were assessed according to the resistance genotypes. MICs were determined for all strains of pneumococci using an agar dilution method. MLS(B) resistance phenotypes were determined by the double disk (erythromycin A and clindamycin) diffusion method. Genetic determinants for macrolide resistance were identified by PCR using primers specific for erm(B) and mef(A). Erythromycin A resistance was detected in 13.8% of the strains. MLS(B) resistance phenotype was observed in 82% of these (60% being cMLS(B) and 40% being iMLS(B)), and M type resistance in about 18%. All the MLS(B) phenotype strains except four, revealed the presence of erm(B) gene and all except one M phenotype strains revealed the mef(A) gene. Of the erythromycin A resistant pneumococci about 49% were also resistant to clindamycin. No strains were resistant to telithromycin, quinupristin/dalfopristin and linezolid. Telithromycin had the lowest MIC values for both erythromycin A resistant and susceptible strains of all the antiribosomal agents tested. The most prevalent mechanism of macrolide resistance was mediated by the erm(B) gene leading to the expression of MLS(B) phenotype. Telithromycin was the most active antiribosomal agent, regardless of the macrolide resistance genotype of the pneumococci tested.

Efficacy and tolerability of once-daily oral telithromycin compared with clarithromycin for the treatment of community-acquired pneumonia in adults

BACKGROUND

Telithromycin is a new antibacterial agent of the ketolide class designed to provide optimal treatment against common bacterial respiratory tract pathogens. Telithromycin was derived by structural modification of the basic macrolide molecule to allow tight binding to the bacterial ribosome that enhances potency and minimizes the risk for the development of resistant strains.

OBJECTIVE

The aim of this study was to compare the efficacy and tolerability of telithromycin 800 mg once daily with those of high-dose clarithromycin (500 mg twice daily), each for 10 days, in the treatment of adult patients with community-acquired pneumonia (CAP).

METHODS

This randomized, double-blind, double-dummy, parallel-group clinical trial was conducted at 54 centers in the United States, Canada, Argentina, and Chile. Patients aged >or=18 years with acute CAP were randomized to receive 10-day treatment with oral telithromycin 800 mg once daily (administered as two 400-mg encapsulated tablets in the morning) and placebo (administered as 2 encapsulated tablets identical to the telithromycin in the evening) or high-dose clarithromycin (500 mg administered as two 250-mg identical encapsulated tablets twice daily). The primary outcome measure was clinical outcome at the posttherapy, test-of-cure visit (days 17-24 after the completion of therapy) in the clinically assessable per-protocol population. Secondary efficacy variables included bacteriologic outcome at the posttherapy, test-of-cure visit, and clinical and bacteriologic outcomes at the late posttherapy visit (day 31-45). Tolerability was assessed using investigator observation, patient self-reporting, clinical laboratory data, a 12-lead electrocardiogram, and physical examination (including vital signs).

RESULTS

A total of 493 patients were enrolled and 448 patients received >or=1 dose of study medication (224 patients/group). A diagnosis of CAP was confirmed in 416 patients (205 men, 211 women; median age, 43 years; telithromycin, n = 204; clarithromycin, n = 212). Clinical cure rates were 88.3% (143/162) in the telithromycin group and 88.5% ( 138/56) in the clarithromycin group. Bacterial eradication rates were comparable between treatment groups (telithromycin, (28/32) [87.5%]; clarithromycin, (29/30) [96.7%]. Both treatment were fairly well tolerated; adverse events were experienced in 57.0% of the patients treated with telithromycin and 49.1% of those treated with clarithromycin; most of these were assessed as mild.

CONCLUSIONS

In this study of adult patients with CAP, telithromycin 800 mg once daily was an effective and fairly well-tolerated regimen for initial empiric treatment, with clinical and bacteriologic efficacy and tolerability equivalent to therapy with high-dose clarithromycin (500 mg twice daily).

Activities of cethromycin and telithromycin against recent North American isolates of Streptococcus pneumoniae

The in vitro activities of two investigational ketolides, cethromycin (formerly ABT-773) and telithromycin, were determined for a selected group of 312 Streptococcus pneumoniae isolates from a national surveillance program. The MIC of cethromycin at which 50% of the isolates were inhibited was 0.008 micro g/ml, and the MIC at which 90% of the isolates were inhibited was 0.06 micro g/ml; the corresponding values for telithromycin were </=0.015 and 0.25 micro g/ml, respectively. For six quinupristin-dalfopristin-resistant strains, the cethromycin MICs were 0.25 to 16 micro g/ml and the telithromycin MICs were 1 to 4 micro g/ml. However, there was only 0.3% resistance to telithromycin.

Clinical and bacteriological efficacy of the ketolide telithromycin against isolates of key respiratory pathogens: a pooled analysis of phase III studies

A pooled analysis of data from 13 phase III studies of telithromycin in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis, acute sinusitis or group A beta-haemolytic streptococcal pharyngitis and tonsillitis was undertaken. Causative key respiratory tract pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus and Streptococcus pyogenes) were isolated at entry to the studies from cultures of relevant respiratory samples and tested for their susceptibility to telithromycin, penicillin and macrolides (erythromycin A). The combined clinical and bacteriological efficacy of telithromycin at the post-therapy, test-of-cure visit (days 17-24) was assessed in patients from whom a microbiologically evaluable pathogen was isolated at entry. More than 98% of key respiratory pathogens isolated, including penicillin G- and macrolide (erythromycin A)-resistant strains of S. pneumoniae, demonstrated full or intermediate susceptibility to telithromycin in vitro at the breakpoints of < or = 1.0 mg/L (susceptible) and 2.0 mg/L (intermediate) used for the purpose of evaluating the susceptibility of isolates recovered during the clinical trials. Treatment with telithromycin 800 mg once-daily for 5, 7 or 7-10 days resulted in high rates of clinical cure (88.5%) and a satisfactory bacteriological outcome (88.9%), similar to the figures seen with comparator antibacterial agents. Clinical cure and eradication rates were good for all key respiratory pathogens, including penicillin G- and macrolide (erythromycin A)-resistant S. pneumoniae. The results suggest that telithromycin will provide effective empirical therapy for community-acquired upper and lower respiratory tract infections.

Telithromycin

Telithromycin, the first member of the ketolide antibacterials, has good activity against community-acquired respiratory pathogens, including multiple-drug-resistant strains of Streptococcus pneumoniae. Telithromycin 800 mg once daily has been US FDA approved for the treatment of acute bacterial sinusitis (ABS; treatment duration 5 days), acute bacterial exacerbations of chronic bronchitis (AECB; 5 days) and mild-to-moderate community-acquired pneumonia (CAP; 7-10 days). In patients with CAP, telithromycin was as effective as amoxicillin 1000 mg three times daily for 10 days, clarithromycin 500 mg twice daily for 10 days or trovafloxacin 200 mg once daily for 7-10 days. In patients with AECB, telithromycin was as effective as a 10-day regimen of amoxicillin/clavulanic acid 500/125 mg three times daily, cefuroxime axetil 500 mg twice daily or clarithromycin 500 mg twice daily. In patients with ABS, telithromycin was as effective as a 10-day course of amoxicillin/clavulanic acid 500/125 mg three times daily or cefuroxime axetil 250 mg twice daily. Telithromycin was generally well tolerated and most adverse events were of mild-to-moderate severity and transitory. The most common adverse events with telithromycin were diarrhoea and nausea (10.8% and 7.9% of 2702 patients in clinical trials); these events occurred in 8.6% and 4.6% of 2139 comparator-treated patients.

Antimicrobial resistance among pediatric respiratory tract infections: clinical challenges

Considerable development of antimicrobial resistance has occurred in the major pediatric bacterial pathogens, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. However, most of the respiratory infections that children suffer are viral and self-limiting, and only a small percentage of them will develop secondary bacterial infections with the pathogens listed. The challenge for rational antibiotic use is to determine which patients can be treated conservatively and which require antimicrobial intervention to avoid prolonged discomfort or development of permanent sequelae. The basis for rational use of antibiotic in the era of resistance in these major pathogens is to avoid overuse of antimicrobial agents, tailor treatment to identified pathogens as much as possible, and base empiric treatment on the disease being treated and the susceptibility of the probable pathogens at breakpoints based on pharmacokinetic and pharmacodynamic parameters. With appropriate dosing regimens based on these parameters and despite development of resistance, amoxicillin is still one of the most active oral agents against S. pneumoniae and non-beta-lactamase producing strains of H. influenzae, whereas amoxicillin-clavulanate is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis. Parenteral ceftriaxone and oral and parenteral fluoroquinolones are active against all 3 species, but fluoroquinolones should be used with utmost caution when all other options have been considered because of concerns about toxicity and development of resistance. Introduction of a 7-valent conjugate pneumococcal vaccine in the United States in 2000 reduced the prevalence of invasive pneumococcal disease in children younger than 2 years old, but, as of 2001, had not had a major impact on decreasing antimicrobial resistance.

Ketolides: a new class of antibacterial agents for treatment of community-acquired respiratory tract infections in a primary care setting

Pathogens implicated in community-acquired respiratory tract infections are becoming increasingly resistant to anti-bacterial therapies. Thus, there is an urgent need for new agents with activity against current resistant respiratory tract pathogens and a low potential to select for resistance or induce cross-resistance to existing antibacterial agents. Telithromycin, the first ketolide antibacterial agent to undergo clinical development, has enhanced binding to bacterial ribosomal RNA. Through its unique structure, telithromycin retains activity against resistant respiratory pathogens and has shown high efficacy in the treatment of respiratory tract infections. On the basis of phase 3 clinical trial experience, telithromycin appears safe and well tolerated across various patient populations, including high-risk groups.

Efficacy and Tolerability of Telithromycin for 5 or 10 Days vs Amoxicillin/Clavulanic Acid for 10 days in Acute Maxillary Sinusitis

Telithromycin (HMR 3647) is a new ketolide antimicrobial that was developed for the treatment of community-acquired respiratory tract infections. We conducted a randomized, double-blind, multicenter study to compare the clinical efficacy and safety of oral telithromycin, at 800 mg once daily for 5 or 10 days, with that of amoxicillin/clavulanic acid, at 500/125 mg three times daily for 10 days, in adults with acute maxillary sinusitis (AMS). A total of 754 patients with AMS of less than 28 days’ duration were randomized to receive either telithromycin for 5 days followed by placebo for 5 days, telithromycin for 10 days, or amoxicillin/clavulanic acid for 10 days. Clinical outcome was assessed at a test-of-cure (TOC) visit between days 17 and 24 and at a late post-therapy visit between days 31 and 45. Analysis of clinical outcome on a per-protocol basis (n = 434) demonstrated therapeutic equivalence among the three regimens at the TOC visit; in each treatment group, the clinical cure rate was approximately 75%. Only a few patients (3 to 5 in each group) had relapsed by the late post-therapy follow-up visit. Telithromycin was generally safe and well tolerated. The most common adverse events were mild or moderate gastrointestinal effects, which occurred with similar frequency in all three groups. We conclude that 5 or 10 days of telithromycin at 800 mg once daily is as effective clinically and as well tolerated as 10 days of treatment with amoxicillin/clavulanic acid. Telithromycin, therefore, appears to be a valuable option for the treatment of AMS.

Pharmacokinetics of the ketolide telithromycin after single and repeated doses in patients with hepatic impairment

The pharmacokinetic profiles of single and repeated oral doses of telithromycin 800 mg/day were compared in patients with hepatic impairment and healthy subjects in two open-label, non-randomized, parallel-group, multicentre studies. The maximal plasma concentrations (Cmax) and the area under the plasma concentration-time (AUC) curves for telithromycin were similar in hepatically impaired patients and healthy subjects in the single- and repeated-dose studies. The extent of formation of RU 76363, the major circulating metabolite of telithromycin, was decreased following single and repeated doses in patients with hepatic impairment compared with healthy subjects. In the single-dose study, the Cmax of RU 76363 was 2-fold lower (P<0.01) and the initial elimination half-life (t(1/2lambda1)) was 44% higher (P<0.01). The Cmax and AUC from 0 to 24 h post-dose were approximately 50% lower on Day 1 (P< or =0.01) and Day 7 (P< or =0.001) in the repeated-dose study. The terminal elimination half-life (t(1/2lambdaz)) of telithromycin was 1.4-fold higher (P<0.001) in the hepatically impaired patients compared with the healthy subjects in the single-dose study. However, t(1/2lambda1) and t(1/2lambdaz) were similar after repeated doses in both populations, suggesting that the decrease in formation of RU 76363 is compensated by an increase in clearance via other pathways. Telithromycin 800 mg was well tolerated in both populations. In conclusion, a once-daily dose of telithromycin is well tolerated in patients with hepatic impairment. Exposure to telithromycin was comparable in patients with hepatic impairment and healthy subjects and thus, no dosage adjustment is required in this patient group providing renal function is not severely impaired.

Comparative in vitro activity of telithromycin and beta-lactam antimicrobials against bacterial pathogens from community-acquired respiratory tract infections: data from the first year of PROTEKT (1999-2000)

The in vitro activity of telithromycin, a new ketolide, was compared with beta-lactam antimicrobials against pathogens commonly associated with community-acquired respiratory tract infections. These pathogens were collected during 1999-2000 as part of the ongoing PROTEKT surveillance study. Globally, penicillin nonsusceptibility among Streptococcus pneumoniae (n = 3362) was 36.3%, ranging from 21.5% (Australasia) to 68.0% (Far East). Telithromycin showed higher potency (MIC90 0.12 mg/L) than beta-lactams against S. pneumoniae; 99.9% of all and 99.6% of multi-resistant isolates were susceptible to telithromycin. Among Streptococcus pyogenes isolates (n = 1485), 100% were susceptible to beta-lactams, and the telithromycin MIC50 and MIC90 were both 0.015 mg/L. Among Haemophilus influenzae (n = 2948), 16.6% produced beta-lactamase, which reduced the activity of ampicillin, cefaclor and cefprozil. 99.9% of H. influenzae were susceptible to telithromycin and the MIC range for M. catarrhalis was 0.004-0.5 mg/L. The first year results of PROTEKT confirmed high potency for telithromycin against common respiratory tract pathogens, including beta-lactam-resistant strains.

Activity of telithromycin against penicillin-resistant Streptococcus pneumoniae isolates recovered from French children with invasive and noninvasive infections

We compared the activities of telithromycin, erythromycin, azithromycin, josamycin, penicillin G, amoxicillin, cefpodoxime, and ceftriaxone against invasive and noninvasive non-penicillin-susceptible Streptococcus pneumoniae isolates recovered from children. Of the 186 isolates tested, 89% were positive for erm(B) by PCR. Telithromycin had the lowest MICs, with MICs at which 90% of the isolates tested are inhibited of 0.032 and 0.25 micro g/ml for erythromycin-sensitive and -resistant isolates, respectively.

Activity of telithromycin and seven other agents against 1034 pediatric Streptococcus pneumoniae isolates from ten central and eastern European centers

OBJECTIVE

To test the activity of telithromycin against 1034 Streptococcus pneumoniae isolates from pediatric patients in ten centers from ten central and eastern European countries during 2000-2001, and to compare it with the activities of erythromycin A, azithromycin, clarithromycin, clindamycin, and quinupristin-dalfopristin.

METHODS

The minimum inhibitory concentrations (MICs) of telithromycin, erythromycin A, azithromycin, clarithromycin, clindamycin, levofloxacin, quinupristin-dalfopristin and penicillin G were tested by the agar dilution method with incubation in air, and mechanisms of resistance to macrolides and quinolones were investigated.

RESULTS

Strains were isolated from sputum, tracheal aspirates, ear, eye, blood, and cerebrospinal fluid. Among S. pneumoniae strains tested, 36% had raised penicillin G MICs (>/= 0.12 mg/L). Susceptibilities were as follows: telithromycin, quinupristin-dalfopristin and levofloxacin, >/= 99%; clindamycin, 83%; and erythromycin A, azithromycin and clarithromycin, 78%. Of 230 (22.3%) erythromycin A-resistant S. pneumoniae strains, 176 (79.6%) had erm(B), 38 (16.1%) had mef(A), and 10 (4.3%) had mutations in 23S ribosomal RNA or in ribosomal protein L4. The rates of drug-resistant S. pneumoniae are high in all centers except Kaunas, Riga, and Prague.

CONCLUSION

Telithromycin had low MICs against all strains, irrespective of macrolide, azalide or clindamycin resistance. Ribosomal methylation was the most prevalent resistance mechanism among all resistant strains, except in Sofia, where the prevalence of the efflux mechanism was higher.

Activity of telithromycin compared with seven other agents against 1039 Streptococcus pyogenes pediatric isolates from ten centers in central and eastern Europe

In total, 1039 pediatric Streptococcus pyogenes isolates from Bulgaria, Croatia, the Czech Republic, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia and Slovenia were studied. All strains were susceptible to penicillin G, levofloxacin, and quinupristin-dalfopristin, 91-100% to telithromycin, and 82-100% to erythromycin, azithromycin, and clarithromycin, and 90-100% to clindamycin. Macrolide resistance occurred mainly in Slovakia (25%), the Czech Republic (17.3%), and Croatia (15.8%). Overall, 9.7% of S. pyogenes isolates were erythromycin resistant due to erm(B)- or erm(A)-encoded methylases (72.3%) or to a mef(A)-encoded efflux pump (25.7%). One strain had alterations of both 23S rRNA (A2058G Escherichia coli numbering) and ribosomal protein L22 (G95D).