ru-66647 and Disease-Models--Animal

As we face an alarming increase in bacterial resistance to current antibacterial chemotherapeutics, expanding the available therapeutic arsenal in the fight against resistant bacterial pathogens causing respiratory tract infections is of high importance. The antibacterial potency of macrolones, a novel class of macrolide antibiotics, against key respiratory pathogens was evaluated in vitro and in vivo MIC values against Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, and Haemophilus influenzae strains sensitive to macrolide antibiotics and with defined macrolide resistance mechanisms were determined. The propensity of macrolones to induce the expression of inducible erm genes was tested by the triple-disk method and incubation in the presence of subinhibitory concentrations of compounds. In vivo efficacy was assessed in a murine model of S. pneumoniae-induced pneumonia, and pharmacokinetic (PK) profiles in mice were determined. The in vitro antibacterial profiles of macrolones were superior to those of marketed macrolide antibiotics, including the ketolide telithromycin, and the compounds did not induce the expression of inducible erm genes. They acted as typical protein synthesis inhibitors in an Escherichia coli transcription/translation assay. Macrolones were characterized by low to moderate systemic clearance, a large volume of distribution, a long half-life, and low oral bioavailability. They were highly efficacious in a murine model of pneumonia after intraperitoneal application even against an S. pneumoniae strain with constitutive resistance to macrolide-lincosamide-streptogramin B antibiotics. Macrolones are the class of macrolide antibiotics with an outstanding antibacterial profile and reasonable PK parameters resulting in good in vivo efficacy.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Disease Models, Animal; Drug Resistance, Bacterial; Escherichia coli; Haemophilus influenzae; Ketolides; Lincosamides; Macrolides; Male; Methyltransferases; Mice; Mice, Inbred C57BL; Pneumonia, Pneumococcal; Protein Biosynthesis; Protein Synthesis Inhibitors; Staphylococcus aureus; Streptococcus pneumoniae; Streptococcus pyogenes; Streptogramin B; Structure-Activity Relationship

The in vitro and in vivo activities of modithromycin, a novel bicyclolide, against Legionella pneumophila were compared with those of telithromycin, clarithromycin, azithromycin, and levofloxacin. All the test agents decreased the intracellular growth of viable L. pneumophila bacteria over 96 h of incubation in both types of cells used, A/J mouse-derived macrophages and A549 human alveolar epithelial cells, at extracellular concentrations of 4× and 16× MIC, respectively. However, when the agents were removed from the medium after exposure for 2 h, regrowth of intracellular bacteria occurred in both cell systems when they were exposed to telithromycin, clarithromycin, and levofloxacin but not when they were exposed to modithromycin and azithromycin. Once-daily administration of modithromycin at a dose of 10 mg/kg of body weight for 5 days led to a significant decrease of intrapulmonary viable L. pneumophila bacteria in immunosuppressed A/J mice. The efficacy of modithromycin was superior to the efficacies of telithromycin and clarithromycin and comparable to the efficacies of azithromycin and levofloxacin. In addition, modithromycin and azithromycin inhibited the intrapulmonary regrowth of bacteria even at 72 h after the last treatment, but telithromycin and levofloxacin did not. These results suggested that modithromycin has longer-lasting cellular pharmacokinetic features like azithromycin. In conclusion, modithromycin, as well as azithromycin, has excellent in vitro and in vivo bactericidal activities and persistent efficacy against intracellular L. pneumophila. Modithromycin should be a useful agent for treatment of pulmonary infections caused by this pathogen.

Topics: Animals; Anti-Bacterial Agents; Azithromycin; Bridged-Ring Compounds; Cell Line; Cells, Cultured; Clarithromycin; Disease Models, Animal; Humans; Ketolides; Legionella pneumophila; Legionnaires' Disease; Levofloxacin; Macrolides; Mice; Microbial Sensitivity Tests; Ofloxacin

The ketolide antibiotic telithromycin (TEL) exerts immunomodulatory and antiinflammatory effects in vitro and in a mouse model of septic shock. We studied the antiinflammatory activity of TEL in in vitro and in vivo models of airway inflammation induced by lipopolysaccharide (LPS).. We measured the effects of TEL on the response of RAW 264.7 macrophages to LPS and of murine lung epithelial (MLE)-12 cells to supernatants of LPS-stimulated RAW 264.7 macrophages. Macrophage inflammatory protein (MIP)-2 and tumor necrosis factor (TNF)-alpha production, nuclear factor (NF)-kappaB activation, and apoptosis were determined. Acute airway inflammation was induced in untreated and TEL-treated BALB/c mice by nebulization with LPS. Total number of leukocytes, macrophages, and neutrophils, the protein concentration, and nitrite and cytokine levels were determined in the BAL fluid.. TEL inhibited in a dose-dependent manner the production of MIP-2 and TNF-alpha by LPS-stimulated RAW 264.7 macrophages, and the production of MIP-2 by MLE-12 epithelial cells to supernatants of LPS-stimulated RAW 264.7 macrophages. NF-kappaB activation was inhibited and apoptosis was increased in both cell lines by TEL. The LPS-induced influx of neutrophils in BAL fluid was decreased by TEL pretreatment. TEL also reduced protein, nitrite, MIP-2, and TNF-alpha levels in the BAL fluid of LPS-nebulized animals.. We have provided evidence that TEL exerts potent antiinflammatory effects in LPS-induced airways injury. We propose that TEL acts in the early phase of inflammation by reducing the release of inflammatory mediators through NF-kappaB inhibition, and in the later phase through enhancement of inflammatory cell apoptosis.

Topics: Animals; Anti-Bacterial Agents; Apoptosis; Bronchoalveolar Lavage Fluid; Cell Line; Cells, Cultured; Chemokine CXCL2; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Ketolides; Lipopolysaccharides; Macrophages; Mice; Mice, Inbred BALB C; NF-kappa B; Pneumonia; Respiratory Mucosa; Tumor Necrosis Factor-alpha

The 14-membered macrolides, such as clarithromycin (CAM) and erythromycin (EM), are effective against diffuse panbronchiolitis. However, there have been no studies on the effects of telithromycin (TEL) on chronic respiratory infection in vivo. In this study, we determined the effect of TEL on an experimental murine model of chronic respiratory infection caused by Pseudomonas aeruginosa with biofilm formation. TEL significantly reduced the number of viable bacteria but had no effect on the proliferation of lymphocytes. In contrast, CAM decreased the number of lymphocytes but had no effect on the number of viable bacteria in the lung. These results suggest that TEL and CAM have different effects on chronic respiratory infection caused by P. aeruginosa.

Topics: Animals; Anti-Bacterial Agents; Biofilms; Chronic Disease; Clarithromycin; Disease Models, Animal; Ketolides; Lung; Lymphocytes; Male; Mice; Pseudomonas aeruginosa; Pseudomonas Infections; Respiratory Tract Infections

Topics: Animals; Anti-Inflammatory Agents; Cytokines; Disease Models, Animal; Female; Ketolides; Lipopolysaccharides; Mice; Mice, Inbred BALB C; Nitric Oxide; Shock, Septic

Human studies support the use of beta-lactams and tetracyclines in the treatment of leptospirosis. Additional agents from these and other classes of antimicrobials also have in vitro activity against Leptospira species, though corroborating in vivo data are limited or lacking. We evaluated the therapeutic efficacy of azithromycin, clarithromycin, and telithromycin in a lethal hamster model of leptospirosis using Leptospira interrogans serogroup Canicola serovar Portlandvere. A range of dosages for each antimicrobial was given to the infected animals on days 2 through 7 (5 days) of the 21-day survival model. All untreated control animals survived less than 10 days from infection. Ninety to 100% of doxycycline controls, treated for 5 days with 5 mg/kg of body weight of drug, survived to 21 days. Treatment with azithromycin (daily dose: 6.25, 12.5, 25, 50, 100, or 200 mg/kg) resulted in 100% survival at all evaluated doses. Animals receiving 20 mg/kg or more of clarithromycin (daily dose: 1, 5, 10, 15, 20, 40, 60, or 100 mg/kg) had improved survival. Ninety-eight percent of animals treated with telithromycin (daily dose: 1, 5, 10, 15, 20, or 40 mg/kg) survived. We conclude that all agents tested have demonstrated in vivo efficacy in treating acute leptospirosis. These results provide support for further evaluation of macrolide and ketolide antimicrobial agents in human trials.

Topics: Animals; Anti-Bacterial Agents; Azithromycin; Clarithromycin; Cricetinae; Disease Models, Animal; Dose-Response Relationship, Drug; Doxycycline; Female; Ketolides; Leptospira interrogans; Leptospirosis; Macrolides; Mesocricetus; Serotyping; Species Specificity; Survival Analysis

The ketolide telithromycin represents a new subclass of 14-membered semisynthetic macrolides. Because there is evidence that traditional macrolides such as roxithromycin exert anti-inflammatory activity, we investigated the anti-inflammatory action of telithromycin against lipopolysaccharide (LPS)-induced acute systemic inflammation in mice in comparison with roxithromycin.. CD-1 mice were injected intraperitoneally with LPS (1 mg/kg), and the effects of pretreatment with a single intraperitoneal dose of telithromycin (150 mg/kg) or roxithromycin (50 mg/kg) for 2 h on the expression and formation of tumour necrosis factor alpha (TNFalpha), interleukin-1 beta (IL-1beta), interferon gamma (IFNgamma) and inducible nitric oxide synthase (NOS-II) as well as nitric oxide (NO) were analysed at different time points after LPS-treatment. Cytokine and NOS-II mRNA abundance was examined using real-time RT-PCR. Tissue cytokine levels were determined by enzyme-linked immunosorbent assay kits (ELISA); NO levels were measured by colorimetric assay kits.. Pretreatment of mice with telithromycin as well as roxithromycin similarly attenuated the LPS-induced expression and formation of TNFalpha, IL-1beta and IFNgamma. Furthermore, the LPS-induced increase of NOS-II mRNA and the formation of NO were clearly diminished.. These results suggest that the ketolide telithromycin has anti-inflammatory properties like conventional macrolides due to inhibition of the production of proinflammatory cytokines, which leads to a decreased formation of NO in LPS-treated mice. Our data indicate that ketolides may have beneficial therapeutic effects independent of their antibacterial activity.

Topics: Acute Disease; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cytokines; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Ketolides; Lipopolysaccharides; Male; Mice; Mice, Inbred Strains; Nitric Oxide; Organ Specificity; Roxithromycin; Systemic Inflammatory Response Syndrome; Time Factors

Mycoplasma pneumoniae infection has been associated with chronic lung disease. Treatment of chronic pulmonary mycoplasmosis has not been well investigated. BALB/c mice were intranasally inoculated once with M. pneumoniae or with sterile media (uninfected controls). Infected mice were treated with telithromycin or placebo daily for 10 days in the chronic phase of disease (18 months after inoculation). Mice (n=43) were evaluated before therapy and 1 day after completion of telithromycin. Treatment of infected mice with telithromycin at 18 months after infection significantly reduced chronic pulmonary histological inflammation compared with infected mice given placebo; however, this treatment did not improve airway obstruction or airway hyperresponsiveness. Therapy longer than 10 days may be necessary to improve pulmonary function.

Topics: Animals; Anti-Bacterial Agents; Chronic Disease; Disease Models, Animal; Female; Ketolides; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Mycoplasma pneumoniae; Plethysmography; Pneumonia, Mycoplasma

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.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Disease Models, Animal; Drug Resistance, Bacterial; Female; Fluoroquinolones; Ketolides; Macrolides; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Pneumococcal Infections; Protein Synthesis Inhibitors; Streptococcus pneumoniae; Thigh

Incubation in CO(2) resulted in higher (> or =3 doubling dilution) MICs of telithromycin than those found in ambient air for 31.2% of 346 Streptococcus pneumoniae ermB-positive strains. An increased telithromycin MIC in CO(2) was not correlated with loss of its activity in the murine sepsis/peritonitis model.

Topics: Animals; Anti-Bacterial Agents; Bacteremia; Carbon Dioxide; Disease Models, Animal; Humans; Ketolides; Mice; Microbial Sensitivity Tests; Peritonitis; Pneumococcal Infections; Protein Synthesis Inhibitors; Streptococcus pneumoniae

Telithromycin (TEL) is a ketolide antimicrobial agent with in vitro activity against Streptococcus pneumoniae (SPN), including macrolide resistant strains. The purpose of this study was to assess the efficacy of TEL against clinical SPN isolates with various genotypic mutations including the newly recognized ribosomal mutations. Pneumonia was induced in either immunocompetent and immunosuppressed mice. Six isolates were included in the study and all were resistant to azithromycin (AZI) by MIC testing. Three oral regimens of TEL were chosen to simulate the human pharmacokinetic (PK) exposures observed in young healthy, healthy elderly (> or =65 years), and infected subjects. An additional group was given AZI in human simulated doses. Bacterial density in lung was determined after each treatment. Telithromycin administered simulating infected patients showed greater efficacy (i.e., change in logCFU) than the azithromycin treated group for all isolates except P1660008. The immune system was responsible for increased efficacy (ranging from 45-146%) for all but one of the telithromycin treatment regimens. Unlike other isolates studied in this in vivo model, P1660008 displayed a highly variable response to therapy, such that the reductions in CFU were not consistent with the microbiological and PK profiles of either compound. For all other isolates, the activity of AZI was comparable with untreated controls. Human simulated exposures of TEL displayed 0.5-3.4 log kill in vivo despite the ribosomal mutations studied. These data support the in vivo efficacy of TEL against a variety of genotypic resistance profiles observed in pneumococci, however, additional studies are required to fully characterize the killing profile of the compound against these recently determined ribosomal mutations.

Topics: Administration, Oral; Animals; Anti-Bacterial Agents; Azithromycin; Colony Count, Microbial; Disease Models, Animal; Drug Resistance, Bacterial; Genes, rRNA; Ketolides; Lung; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Mutation; Pneumonia, Pneumococcal; Streptococcus pneumoniae

An experimental Streptococcus pneumoniae pneumonia model in rabbits was used to assess the efficacy of amoxycillin, erythromycin and a new ketolide, telithromycin (HMR 3647). The MICs of amoxycillin, erythromycin and HMR 3647 for the three clinical S. pneumoniae strains used were, respectively, (mg/L): 0.01, 16 and 0.02 (strain 195); 2, 0.25 and 0.02 (strain 16089); 8, >64 and 0.02 (strain 11724). Antibiotic therapy reproduced human serum pharmacokinetics (amoxycillin 1 g iv tds or erythromycin 500 mg qds or HMR 3647 800 mg bd). Forty-eight hours of therapy with HMR 3647 and amoxycillin resulted in significant bacterial clearance in the lungs and spleen of rabbits infected by S. pneumoniae strain 195 and strain 16089 (at least 3 log(10) cfu/g decrease, P < 0.001). Erythromycin was active against only the erythromycinsusceptible strain (3 log(10) cfu/g decrease at 48 h, P < 0.001). None of the antibiotics showed significant efficacy with strain 11724. All agents produced significant bacterial clearance when time above MBC was >33%, and microbiological failure when it was <25%, whereas MIC was not correlated with microbiological outcome with HMR 3647. Our findings suggest that pharmacodynamic data integrating MBC may be predictive of microbiological success or failure with greater accuracy than with MIC. HMR 3647 produced significant bacterial clearance in both penicillin- and erythromycin-resistant pneumonia, but was less effective against the highly erythromycin-resistant S. pneumoniae strain.

Topics: Amoxicillin; Animals; Anti-Bacterial Agents; Disease Models, Animal; Erythromycin; Humans; Ketolides; Macrolides; Male; Penicillins; Pneumonia, Pneumococcal; Rabbits; Streptococcus pneumoniae; Treatment Outcome

We used a mouse peritonitis model to evaluate the in vivo efficacy of telithromycin (HMR 3647) (TEL) and erythromycin (ERY) against four strains of Enterococcus faecalis and three strains of Enterococcus faecium with differing susceptibilities to TEL. TEL was highly active in vivo against Ery-susceptible (Ery(s)) and -intermediate (Ery(i)) strains (MIC of TEL = 0.015 to 0.062 microg/ml) and showed less efficacy against Ery-resistant (Ery(r)) isolates (MIC of TEL = 4 to 16 microg/ml), although this was overcome in part by a second subcutaneous dose. Quinupristin-dalfopristin was also noted to have less efficacy against Ery(r) versus Ery(s) or Ery(i) E. faecium strains, but this difference was reduced by intravenous administration. In conclusion, TEL was more potent in vivo against enterococci than was ERY; its activity was lowered by the presence of erm(B)-mediated Ery(r).

Topics: Animals; Anti-Bacterial Agents; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Resistance, Microbial; Enterococcus; Erythromycin; Ketolides; Macrolides; Mice; Microbial Sensitivity Tests; Peritonitis

HMR 3647 is a novel macrolide derivative with a broad spectrum of activity against grampositive bacteria and some fastiduous gramnegative bacteria, anaerobes and Toxoplasma gondii. In this work, its activity against the facultatively intracellular bacterium, Listeria monocytogenes, was examined in vitro, in tissue culture and in animal models of systemic and intracerebral infection and compared with that of erythromycin. All strains of L. monocytogenes were susceptible to the substance, with minimal inhibitory concentrations (MICs) that were consistently lower than the MICs of erythromycin. HMR 3647 was bacteriostatic against L. monocytogenes since concentrations of up to 64 times the MIC did not kill the bacteria within 24 hours. HMR 3647 produced a pronounced postantibiotic effect (PAE) and was bacteriostatic in tissue culture cells infected with L. monocytogenes. In animal models of systemic and intracerebral infection, HMR 3647 was slightly more effective than erythromycin in the livers and spleens and comparably effective in the brains when given in the same dosage. In conclusion, HMR 3647 is a candidate substance for the treatment of infections with L. monocytogenes in immunocompetent subjects.

Topics: Animals; Anti-Bacterial Agents; Brain Diseases; Cell Line; Disease Models, Animal; Female; Ketolides; Listeria monocytogenes; Listeriosis; Macrolides; Mice; Microbial Sensitivity Tests