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PubMed1994

Recombinant granulocyte-macrophage colony-stimulating factor enhances the effects of antibiotics against Mycobacterium avium complex infection in the beige mouse model.

Previous studies have shown that recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates human and murine macrophages to inhibit growth and kill intracellularly. This study shows the effect of GM-CSF on Mycobacterium avium complex (MAC) infection in vivo using a C57BL/6 beige mouse model of disseminated MAC infection. Furthermore, it examined the activity of the combination of GM-CSF and amikacin or azithromycin, two antimicrobials active against MAC, on the survival of MAC within macrophages in vitro and in the mouse model of disseminated infection. Although GM-CSF (25 mg/kg) induced mycobactericidal and mycobacteriostatic activity in macrophages in vitro and in vivo, the combination of GM-CSF and amikacin (50 mg/kg) or azithromycin (250 mg/kg) was associated with a significant increase in killing of MAC both within cultured macrophages and in the beige mouse model. Therefore, a significant reduction in the number of viable bacteria was observed in blood, liver, and spleen of mice treated with a combination of GM-CSF and azithromycin or amikacin compared with control mice and those treated with GM-CSF or antimicrobials alone.

Amikacin↗

PubMed2002

Effect of gemifloxacin on viability of Chlamydia pneumoniae (Chlamydophila pneumoniae) in an in vitro continuous infection model.

Persistent infection with Chlamydia pneumoniae (Chlamydophila pneumoniae) has been implicated in the development of atherosclerosis, asthma and other chronic diseases. However, data on treatment of C. pneumoniae infections are limited. Microbiological failure of antimicrobial therapy has been described, even after prolonged courses of treatment with azithromycin, doxycycline and erythromycin. Gemifloxacin is an enhanced-affinity fluoroquinolone with excellent activity against most common respiratory pathogens, including C. pneumoniae. The effect of prolonged treatment with gemifloxacin, compared with azithromycin, on viability of C. pneumoniae was investigated in a continuous infection model. Gemifloxacin at final con-centrations of 0.25 and 2.5 mg/L reduced the viability of C. pneumoniae by 5 log(10), which was similar to the effect of azithromycin. However, both antimicrobials failed to completely eliminate C. pneumoniae from continuously infected cells, even after 30 days of treatment. Both antibiotics decreased levels of interleukin-6 and interleukin-8 in this model, but this effect appeared to be secondary to the antichlamydial activity, as the cytokine levels correlated with the concentrations of microorganisms.

Anti-Bacterial Agents↗

PubMed2004

Anti-inflammatory effects of macrolides--an underappreciated benefit in the treatment of community-acquired respiratory tract infections and chronic inflammatory pulmonary conditions?

BACKGROUND: It has been recognized for more than 20 years that the macrolides have immunomodulatory effects that are beneficial for those suffering from chronic pulmonary inflammatory syndromes, such as diffuse panbronchiolitis, cystic fibrosis, asthma and bronchiectasis. The macrolides have consistently been associated with decreased length of stay and mortality when used alone or in combination with beta-lactam antibiotics. This effect can be demonstrated against combinations consisting of beta-lactams and other antibiotics active against 'atypical chest pathogens' when treating community-acquired pneumonia (CAP) in hospitalized patients. As such, it appears that the macrolides' effects in CAP patients are more than just antibacterial in nature. AIMS OF THIS REVIEW: This review aims: to give the reader information on the background areas described, as well as related areas; to review the CAP benefits with macrolides and how they may be related to the immunomodulatory properties they demonstrate, albeit in a shorter period of time than previously demonstrated with chronic pulmonary disorders; to use ex vivo data to support these extrapolations. LITERATURE SEARCH: A literature search using Medline was conducted from 1966 onwards, searching for articles with relevant key words such as macrolide, diffuse panbronchiolitis, community-acquired pneumonia, biofilm, immunomodulation, cystic fibrosis, erythromycin, clarithromycin, roxithromycin and azithromycin, bronchiectasis and asthma. When appropriate, additional references were found from the bibliographies of identified papers of interest. Any relevant scientific conference proceedings or medical texts were checked when necessary. CONCLUSIONS: (1) Research into macrolide immunomodulation for chronic pulmonary disorders demonstrates consistent positive effects, although of types other than seen with diffuse panbronchiolitis. These effects, together with their inhibitory activity on biofilms, have the potential to make them a useful option. (2) The benefits for CAP are consistent, and higher when a macrolide is given with another atypical agent than if the other atypical agent is given alone, suggesting a non-antibacterial benefit. (3) Recent research of the immunomodulatory properties of azithromycin imply that azithromycin may have a previously unknown short-term biphasic effect on inflammation modulation: enhancement of host defence mechanisms shortly after initial administration followed by curtailment of local infection/inflammation in the following period. (4) Additional in vivo research is needed prior to developing any firm conclusions.

Anti-Bacterial Agents↗

PubMed2003

Eradication of Cryptosporidium in four children with acute lymphoblastic leukemia.

Four children on chemotherapy for acute lymphoblastic leukemia presented with severe diarrhea and dehydration. Cryptosporidium was identified in the stools using modified Ziehl-Neelsen stain. Two of them received paromomycin and responded well. One was started on paromomycin for 10 days and although there was clinical improvement, his stools examination continued to be positive for Cryptosporidium. He then received azithromycin for 10 days. He responded well and his stools became negative for Cryptosporidium. The fourth patient received azithromycin from the start and responded well. Cryptosporidium should be considered in all immunocompromised children with severe or prolonged diarrhea, and since it is not seen in a routine ova and parasite examination, the laboratory should be notified for diagnostic confirmation using modified Ziehl-Neelsen stain. Immunocompromised children with Cryptosporidium diarrhea may benefit from paromomycin or azithromycin therapy.

Amebicides↗

PubMed1997

Macrolides in the management of streptococcal pharyngitis/tonsillitis.

The most frequent bacterial cause of pharyngitis/tonsillitis, a common infection in children, is group A beta-hemolytic streptococci. Prevention of acute rheumatic fever is the principal goal of treatment, although antibiotic therapy may also relieve the signs and symptoms of infection, shorten the infective period and prevent suppurative complications. Penicillin is the drug of choice. Alternatives are required, however, for patients allergic to penicillin and may be needed if the rate of bacteriologic failure with penicillin observed during the past decade continues. Erythromycin is generally effective in this infection, but its use, especially in children, is complicated by the need for multiple daily doses, a lengthy treatment period and a high rate of gastrointestinal side effects. The newer macrolides clarithromycin and azithromycin offer lower rates of gastrointestinal complaints and more convenient dosing. Clarithromycin is recommended for twice daily and azithromycin for once daily administration. Because of its prolonged tissue half-life, the recommended duration of azithromycin therapy is 5 days, compared with 10 days for penicillin, erythromycin and clarithromycin. Newer macrolides are rational alternatives to erythromycin for streptococcal pharyngitis/tonsillitis in penicillin-allergic patients.

Adolescent↗

PubMed1997

In vitro activities of oral antimicrobial agents against penicillin-resistant Streptococcus pneumoniae: implications for outpatient treatment.

We tested 83 penicillin-intermediate (Peni) and 50 penicillin-resistant (Penr) isolates of Streptococcus pneumoniae against eight oral antimicrobials. Clarithromycin's MICs (minimal inhibitory concentration) were generally the same or one to two dilutions less than those of azithromycin. Seventy-two percent of Peni isolates were susceptible to clarithromycin and azithromycin, in contrast to 42% and 40%, respectively, of Penr isolates. Cefuroxime activity exceeded that of cefprozil, which exceeded that of cefaclor, in Peni isolates. For all three cephalosporins, MICs of 90% of isolates tested were > or = 3 dilutions higher for Penr isolates than for Peni isolates. Percentages of Peni isolates susceptible to clindamycin and tetracycline were 92% and 83%, respectively, and 78% and 82% for Penr. Only 49% of Peni isolates and 4% of Penr isolates were susceptible to trimethoprim-sulfamethoxazole. Azithromycin, clarithromycin, cefuroxime, cefprozil, clindamycin, and tetracycline may be useful in treating infections caused by Peni S pneumoniae, but Penr isolates are frequently resistant to both old and newer agents.

Administration, Oral↗

PubMed2003

Antibiotic treatment of atherosclerosis.

PURPOSE OF REVIEW: Several lines of evidence have demonstrated an association between a variety of chronic bacterial infections and atherosclerotic cardiovascular disease. This has led to the proposal that antibiotic therapy might be helpful in the secondary prevention of atherosclerosis. A variety of smaller pilot studies have been reported testing this hypothesis and several large multicenter trials are also underway. The purpose of this review is to summarize the results of these studies and comment on their implications for the treatment of atherosclerosis. RECENT FINDINGS: Most of the antibiotic studies to date have been secondary prevention studies that have targeted patients exposed to Chlamydia pneumoniae. Most have used either azithromycin or roxithromycin with treatment courses ranging from a few days to 3 months. Several small studies of coronary artery disease patients have shown significant promise for reducing cardiovascular events such as death, myocardial infarction, or admission for unstable angina. However, other studies have not been so positive. Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders, WIZARD, the largest study to date, in which stable post-myocardial infarction patients were randomized to receive a 3-month course of azithromycin or placebo, demonstrated a significant reduction in death and myocardial infarction by 6 months, but this benefit was not sustained throughout the remaining course of follow-up. The Azithromycin and Coronary Events (ACES) and Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) trials are ongoing and are testing the effect of more prolonged treatment duration. SUMMARY: A variety of antibiotic trials for the secondary prevention of atherosclerosis have been performed. Several pilot studies have shown significant positive clinical effects, but, thus far, no large randomized trial has confirmed those findings. Some concerns over the antibiotics chosen and the duration of treatment have been raised. Other trials are underway to address some of those concerns. In the meantime, no recommendation for the use of antibiotic therapy for the secondary prevention of atherosclerosis can yet be made.

Animals↗

PubMed1998

The pattern of micro-organisms and the efficacy of new macrolide in acute lower respiratory tract infections.

Lower respiratory tract infection (LRTI) is one of the major health problems in developing countries such as Indonesia. According to the National Household Health Survey conducted by the Ministry of Health in 1992, LRTIs still rank fourth as the main cause of death in Indonesia. The problem of LRTIs could be simply managed as long as the causative organism can be identified and the proper antibiotic known. In some occasions, it is not quite so easy to identify the causative micro-organism, especially in lower tract infections. There are several methods of obtaining specimens from LRTIs for cultures. The easiest, most simple way is to collect expectorated sputum. Unfortunately, because of the high rate of contamination by upper respiratory tract flora, this method is not reliable. Recognizing the difficulties with routine expectorated sputum cultures, two alternative approaches have been suggested. One approach is to bypass potential expectorated sputum 'contaminants' in the oropharynx by transtracheal aspiration or transthoracic aspiration. The second approach is to modify the usual technique of processing expectorated sputum by either washing techniques or by quantitative cultures. Azithromycin and clarithromycin are chemically related to macrolide erithromycin. Both antibiotics retain the traditional macrolide spectrum of activity against gram-positive and atypical pneumonia pathogens, while demonstrating improved activity against gram-negative bacteria. The American Thoracic Society (ATS) recommended the use of macrolide for outpatients with community-acquired pneumonia, without comorbidity and 60 years of age or younger. A total of 34 outpatients with acute LRTIs were open-comparative, randomly allocated to treatment with the new macrolide in Persahabatan Hospital, Jakarta, 1996. The purposes of this study were: (i) to identify the causative micro-organisms; and (ii) to evaluate the clinical efficacy of the new macrolide in these infections. Azithromycin 500 mg was given orally once a day for 3 days and was administered 1 h before or 2 h after every meal. Clarithromycin 500 mg was given orally every 12 h for 10 days. The diagnosis of the patients were: 16 with pneumonia, 10 with acute bronchitis and 8 with acute exacerbation of chronic bronchitis. In this study of 34 patients, the sputum specimens were washed with N acetylcysteine before culture and we could only detect micro-organisms in one patient. Before treatment, we found 47 strains in 33 (97.05%) patients and after treatment we found five strains. From serological examination, only four (11.76%) atypical bacterial were detected. The most frequently found microorganisms were 23 strains of Klebsiella pneumoniae (40.42%), 10 of Streptococcus alpha haemolyticus (21.26%), five of Streptococcus pneumoniae (10.63%) and five of Staphylococcus aureus (10.63%). The atypical bacterial were: two Legionella pneumophila, one Mycoplasma pneumoniae and one Chlamydia pneumoniae. The clinical efficacy of new macrolides were 100% and the bacteriological responses with eradication of 94.12% vs 70.59% of isolates in the azithromycin and clarithromycin groups are shown in Table 1. There were no adverse reactions detected in the two treatment groups until the end of the study.

Administration, Oral↗

PubMed1998

A four-day low dose triple therapy regimen for the treatment of Helicobacter pylori infection.

OBJECTIVE: The current guidelines recommend 1-wk triple therapy regimens for eradicating H. pylori infection. Until now, shorter regimens have scarcely been investigated. Azithromycin is a new generation macrolide antibiotic with unusual and favorable pharmacokinetics, and seems to be a very promising agent for innovative anti-H. pylori regimens. We assessed the efficacy and tolerability of a new 4-day low dose triple therapy in comparison with a well established 1-wk triple therapy in the treatment of Helicobacter pylori infection. METHODS: One hundred-sixty consecutive patients with biopsy-proven H. pylori infection were randomized to receive lansoprazole 30 mg b.i.d. on days 1-4, azithromycin 500 mg u.i.d. on days 2-4, and tinidazole 2000 mg u.i.d. on day 3 (LAT group), or 7 days of triple therapy of omeprazole 20 mg u.i.d., clarithromycin 250 mg b.i.d., and tinidazole 500 mg b.i.d. (OCT group). Patients with gastric or duodenal active ulcer received proton pump inhibitors for an additional 4 wk. H. pylori eradication was defined as negative of both rapid urease test and histology on biopsies taken from the gastric body and antrum at least 1 month after the end of treatment. RESULTS: Seven patients in the LAT group and four in the OCT group were lost to follow-up. No significant difference in either efficacy or tolerability was observed between the two regimens. Active ulcers healed in 97.8% of cases with LAT and in 100% of cases with OCT. The eradication rate was 80.8% in the LAT group and 85.5% in the OCT group, considering the per-protocol results, and 73.3% and 81.2%, respectively, considering the intention-to-treat results. Side effects occurred in one LAzT patient and in two OCT patients; they were mild and did not interfere with compliance. CONCLUSION: The new proposed ultrashort triple therapy, including lansoprazole, low dose azithromycin for 3 days, and a single dose of tinidazole, appears to be a very effective anti-H. pylori regimen, a simpler, cheaper, well-tolerated, and equally effective alternative to 1-wk triple therapy.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2003

Prediction of the in vivo interaction between midazolam and macrolides based on in vitro studies using human liver microsomes.

Clinical studies have revealed that plasma concentrations of midazolam after oral administration are greatly increased by coadministration of erythromycin and clarithromycin, whereas azithromycin has little effect on midazolam concentrations. Several macrolide antibiotics are known to be mechanism-based inhibitors of CYP3A, a cytochrome P450 isoform responsible for midazolam hydroxylation. The aim of the present study was to quantitatively predict in vivo drug interactions in humans involving macrolide antibiotics with different inhibitory potencies based on in vitro studies. alpha- and 4-Hydroxylation of midazolam by human liver microsomes were evaluated as CYP3A-mediated metabolic reactions, and the effect of preincubation with macrolides was examined. The hydroxylation of midazolam was inhibited in a time- and concentration-dependent manner following preincubation with macrolides in the presence of NADPH, whereas almost no inhibition was observed without preincubation. The kinetic parameters for enzyme inactivation (K'app and kinact) involved in midazolam alpha-hydroxylation were 12.6 microM and 0.0240 min-1, respectively, for erythromycin, 41.4 microM and 0.0423 min-1, respectively, for clarithromycin, and 623 microM and 0.0158 min-1, respectively, for azithromycin. Similar results were obtained for the 4-hydroxylation pathway. These parameters and the reported pharmacokinetic parameters of midazolam and macrolides were then used to simulate in vivo interactions based on a physiological flow model. The area under the concentration-time curve (AUC) of midazolam after oral administration was predicted to increase 2.9- or 3.0-fold following pretreatment with erythromycin (500 mg t.i.d. for 5 or 6 days, respectively) and 2.1- or 2.5-fold by clarithromycin (250 mg b.i.d. for 5 days or 500 mg b.i.d. for 7 days, respectively), whereas azithromycin (500 mg o.d. for 3 days) was predicted to have little effect on midazolam AUC. These results agreed well with the reported in vivo observations.

Anti-Bacterial Agents↗

PubMed2006

Activities of ceftobiprole, a novel broad-spectrum cephalosporin, against Haemophilus influenzae and Moraxella catarrhalis.

Ceftobiprole, a broad-spectrum pyrrolidinone-3-ylidenemethyl cephem currently in phase III clinical trials, had MICs between 0.008 microg/ml and 8.0 microg/ml for 321 clinical isolates of Haemophilus influenzae and between < or =0.004 microg/ml and 1.0 microg/ml for 49 clinical isolates of Moraxella catarrhalis. Ceftobiprole MIC(50) and MIC(90) values for H. influenzae were 0.06 microg/ml and 0.25 microg/ml for beta-lactamase-positive strains (n = 262), 0.03 microg/ml and 0.25 microg/ml for beta-lactamase-negative strains (n = 40), and 0.5 microg/ml and 2.0 microg/ml for beta-lactamase-negative ampicillin-resistant strains (n = 19), respectively. Ceftobiprole MIC(50) and MIC(90) values for beta-lactamase-positive M. catarrhalis strains (n = 40) were 0.12 microg/ml and 0.5 microg/ml, respectively, whereas the ceftobiprole MIC range for beta-lactamase-negative M. catarrhalis strains (n = 9) was < or =0.004 to 0.03 microg/ml. Ceftriaxone MICs usually were generally at least twofold lower than those of ceftobiprole, whereas amoxicillin-clavulanate MICs usually were higher than those of ceftobiprole. Azithromycin and telithromycin had unimodal MIC distributions against H. influenzae, with MIC(90) values of azithromycin and telithromycin of 2 microg/ml and 4 microg/ml, respectively. Except for selected quinolone-nonsusceptible H. influenzae strains, moxifloxacin proved highly active, with MIC(90) values of 0.12 microg/ml. Time-kill analyses showed that ceftobiprole, ceftriaxone, cefpodoxime, amoxicillin-clavulanate, azithromycin, telithromycin, and moxifloxacin were bactericidal at 2x MIC by 24 h against all 10 H. influenzae strains surveyed. Only modest increases in MICs were found for H. influenzae or M. catarrhalis clones after 50 serial passages in the presence of subinhibitory concentrations of ceftobiprole, and single-passage selection showed that the selection frequency of H. influenzae or M. catarrhalis clones with elevated ceftobiprole MICs is quite low.

Amoxicillin-Potassium Clavulanate Combination↗

PubMed2006

Effect of PEX, a noncatalytic metalloproteinase fragment with integrin-binding activity, on experimental Chlamydophila pneumoniae infection.

Chlamydophila pneumoniae is a pathogen that is involved in acute and chronic respiratory infections and that is associated with asthma and coronary artery diseases. In this study, we evaluated the effects of PEX, a noncatalytic metalloproteinase fragment with integrin-binding activity, against experimental infections caused by C. pneumoniae. Moreover, we investigated the relationships between C. pneumoniae and alpha(v)beta(3) integrin functions in order to explain the possible mechanism of action of PEX both in vitro and in vivo. For the in vitro experiments, HeLa cells were infected with C. pneumoniae and treated with either PEX or azithromycin. The results obtained with PEX were not significantly different (P > 0.05) from those achieved with azithromycin. Similar results were also obtained in a lung infection model. Male C57BL/J6 mice inoculated intranasally with 10(6) inclusion-forming units of C. pneumoniae were treated with either PEX or azithromycin plus rifampin. Infected mice treated with PEX showed a marked decrease in C. pneumoniae counts versus those for the controls; this finding did not differ significantly (P > 0.05) from the results observed for the antibiotic-treated group. Integrin alpha(v)beta(3) plays an important role in C. pneumoniae infection. Blockage of integrin activation led to a significant inhibition of C. pneumoniae infection in HeLa cells. Moreover, CHO(DHFR) alpha(v)beta(3)-expressing cells were significantly (P < 0.001) more susceptible to C. pneumoniae infection than CHO(DHFR) cells. These results offer new perspectives on the treatment of C. pneumoniae infection and indicate that alpha(v)beta(3) could be a promising target for new agents developed for activity against this pathogen.

Animals↗

PubMed1995

Effects of two antibiotic regimens on course and persistence of experimental Chlamydia pneumoniae TWAR pneumonitis.

We studied the effects of two antibiotic regimens on the course of Chlamydia pneumoniae infection in the lungs of Swiss Webster mice. After intranasal challenge with isolates AR-388 (1.3 x 10(7) inclusion-forming units per mouse) and AR-39 (1.5 x 10(6) inclusion-forming units per mouse), groups of animals were treated with either doxycycline (10 mg/kg of body weight once a day for 3 days), azithromycin (10 mg/kg [single dose]), or saline. Responses were assessed by the isolation of organisms in cell culture, detection of TWAR DNA in lung tissues by PCR, and lung histology. Both regimens were effective in clearing infections induced by AR-388 (P = 0.02 and 0.007 for doxycycline and azithromycin, respectively) compared with controls. TWAR DNA was detected in 77 and 25% of culture-negative lungs 2 weeks after treatment of AR-388 and AR-39 infections, respectively. Histological changes showed interstitial pneumonitis and were similar over time for all groups. Single-dose azithromycin produced drug levels in lung tissues above the MICs for the test strains for a period three times longer than that of single-dose doxycycline. We concluded that short-term antibiotic regimens were successful for the treatment of experimental TWAR pneumonitis in mice. TWAR DNA was frequently recovered from lung tissues after apparently successful treatment.

Animals↗

PubMed1996

Effect of recombinant human gamma interferon on intracellular activities of antibiotics against Listeria monocytogenes in the human macrophage cell line THP-1.

Listeria monocytogenes is a facultative intracellular pathogen which enters cells by endocytosis and reaches phagolysosomes from where it escapes and multiplies in the cytosol of untreated cells. Exposure of macrophages to gamma interferon (IFN-gamma) restricts L. monocytogenes to phagosomes and prevents its intracellular multiplication. We have tested whether IFN-gamma also modulates the susceptibility of L. monocytogenes to antibiotics. We selected drugs from three different classes displaying marked properties concerning their cellular accumulation and subcellular distribution, namely, ampicillin (not accumulated by cells but present in cytosol), azithromycin (largely accumulated by cells but mostly restricted to lysosomes), and sparfloxacin (accumulated to a fair extent but detected only in cytosol). We used a continuous line of myelomonocytic cells (THP-1 macrophages), which display specific surface receptors for IFN-gamma, and examined the activity of these antibiotics against L. monocytogenes Hly+ (virulent variant) and L. monocytogenes Hly- (a nonvirulent variant defective in hemolysin production). Untreated THP-1 and phorbol myristate acetate-differentiated THP-1 were permissive for infection and multiplication of intracellular L. monocytogenes Hly+ (virulent variant). All three antibiotics tested were bactericidal against this Listeria strain when added to an extracellular concentration of 10x their MIC. After preexposure of THP-1 to IFN-gamma, L. monocytogenes Hly+ was still phagocytosed but no longer grew intracellularly. The activity of ampicillin became almost undetectable (antagonistic effect), and that of azithromycin was unchanged (additive effect with that of IFN-gamma), whereas that of sparfloxacin was markedly enhanced (synergy). A similar behavior (lack of bacterial growth, associated with a loss of activity of ampicillin, an enhanced activity of sparfloxacin, and unchanged activity of azithromycin) was observed in cells infected with L. monocytogenes Hly-. This modulation of antibiotic activity, which we ascribe to the change of subcellular localization of L. monocytogenes caused by IFN-gamma or by the lack of virulence factor, could result from a change in bacterial responsiveness to antibiotics, a modification of the drug activity, or differences in drug bioavailabilities between cytosol and phagosomes.

Ampicillin↗

PubMed2001

In vitro activity of gemifloxacin (SB-265805, LB20304a) against Legionella pneumophila and its pharmacokinetics in guinea pigs with L. pneumophila pneumonia.

The activity of gemifloxacin against intracellular Legionella pneumophila and for the treatment of guinea pigs with L. pneumophila pneumonia was studied. Gemifloxacin, azithromycin, and levofloxacin (1 microg/ml) reduced bacterial counts of two L. pneumophila strains grown in guinea pig alveolar macrophages by 2 to 3 log(10) units. Gemifloxacin and levofloxacin had roughly equivalent intracellular activities. In contrast, erythromycin had static activity only. Therapy studies of gemifloxacin, azithromycin, and levofloxacin were performed in guinea pigs with L. pneumophila pneumonia. When gemifloxacin (10 mg/kg) was given by the intraperitoneal (i.p.) route to infected guinea pigs, mean peak levels in plasma were 1.3 microg/ml at 0.5 h and 1.2 microg/ml at 1 h postinjection. The terminal half-life phase of elimination from plasma was 1.3 h, and the area under the concentration-time curve from 0 to 24 h (AUC(0--24)) was 2.1 microg. h/ml. For the same drug dose, mean levels in lungs were 3.4 microg/g at both 0.5 and 1 h, with a half-life of 1.5 h and an AUC(0--24) of 6.0 microg. h/ml. All 15 L. pneumophila-infected guinea pigs treated with gemifloxacin (10 mg/kg/dose given i.p. once daily) for 2 days survived for 9 days after antimicrobial therapy, as did 13 of 14 guinea pigs treated with the same dose of gemifloxacin given for 5 days. All 12 azithromycin-treated animals (15 mg/kg/dose given i.p. once daily for 2 days) survived, as did 11 of 12 animals treated with levofloxacin (10 mg/kg/dose given i.p. once daily for 5 days). None of 12 animals treated with saline survived. Gemifloxacin is effective against L. pneumophila in infected macrophages and in a guinea pig model of Legionnaires' disease, even with an abbreviated course of therapy. These data support studies of the clinical effectiveness of gemifloxacin for the treatment of Legionnaires' disease.

Animals↗

PubMed2002

Mutation in 23S rRNA associated with macrolide resistance in Neisseria gonorrhoeae.

Fifty-six azithromycin-resistant (MICs, 2.0 to 4.0 micro g/ml) Neisseria gonorrhoeae strains with cross-resistance to erythromycin (MICs, 2.0 to 64.0 micro g/ml), isolated in Canada between 1997 and 1999, were characterized, and their mechanisms of azithromycin resistance were determined. Most (58.9%) of them belonged to auxotype-serotype class NR/IB-03, with a 2.6-mDa plasmid. Based on resistance to crystal violet (MICs >or= 1 micro g/ml), 96.4% of these macrolide-resistant strains appeared to have increased efflux. Nine of the eleven strains selected for further characterization were found to have a promoter region mtrR mutation, a single-base-pair (A) deletion in the 13-bp inverted repeat, which is believed to cause overexpression of the mtrCDE-encoded efflux pump. The two remaining macrolide-resistant strains (erythromycin MIC, 64.0 micro g/ml; azithromycin MIC, 4.0 micro g/ml), which did not have the mutation in the mtrR promoter region, were found to have a C2611T mutation (Escherichia coli numbering) in the peptidyltransferase loop in domain V of the 23S rRNA alleles. Although mutations in domain V of 23S rRNA alleles had been reported in other bacteria, including E. coli, Streptococcus pneumoniae, and Helicobacter pylori, this is the first observation of these mutations associated with macrolide resistance in N. gonorrhoeae.

Anti-Bacterial Agents↗

PubMed2003

Susceptibilities to levofloxacin in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis clinical isolates from children: results from 2000-2001 and 2001-2002 TRUST studies in the United States.

Among respiratory tract isolates of Streptococcus pneumoniae from children, resistance to penicillins, cephalosporins, macrolides, and trimethoprim-sulfamethoxazole (SXT) increases on an annual basis. Pediatric patients who do not respond to conventional therapy for respiratory tract infections someday may be treated with fluoroquinolones. In this study, MICs of beta-lactams, azithromycin, SXT, and levofloxacin were determined and interpreted by using NCCLS guidelines for isolates of S. pneumoniae (2,834 from children and 10,966 from adults), Haemophilus influenzae (629 from children and 2,281 from adults), and Moraxella catarrhalis (389 from children and 1,357 from adults) collected during the 2000-2001 and 2001-2002 respiratory illness seasons in the United States as part of the ongoing TRUST surveillance studies. Rates of resistance to penicillin, azithromycin, and SXT were > or = 7.5% higher among patients < or = 4 years old than among patients 5 to 10, 11 to 17, and > or = 18 years old in both the 2000-2001 and the 2001-2002 respiratory illness seasons. Levofloxacin resistance was detected in 2 of 2,834 isolates (0.07%) from patients <18 years old. Levofloxacin MICs of 0.25 to 1 micro g/ml accounted for 99.6, 99.5, 99.3, 99.7, 98.4, and 98.0% of isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old. Multidrug resistance was twice as common among patients < or = 4 years old (25.3%) as among patients 5 to 10 years old (13.7%), 11 to 17 years old (11.9%), 18 to 64 years old (12.1%), and > 64 years old (12.4%). The most common multidrug resistance phenotype in S. pneumoniae isolates for all age groups was resistance to penicillin, azithromycin, and SXT (70.3 to 76.6%). For H. influenzae and M. catarrhalis isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old, levofloxacin MICs at which 90% of the isolates were inhibited were 0.015 and 0.03 to 0.06 microg/ml, respectively, in the 2000-2001 and 2001-2002 respiratory illness seasons. In the 2000-2001 and 2001-2002 respiratory illness season surveillance studies in the United States, 99.9% of pediatric isolates of S. pneumoniae were susceptible to levofloxacin. If fluoroquinolones become a treatment option for pediatric patients, careful monitoring of fluoroquinolone susceptibilities will be increasingly important in future surveillance studies.

Adolescent↗

PubMed1999

Can an antibiotic (macrolide) prevent Chlamydia pneumoniae-induced atherosclerosis in a rabbit model?

There is increasing data implicating Chlamydia pneumoniae in the pathogenesis of atherosclerosis, and antibiotics may theoretically be useful to prevent secondary vascular complications. Three groups of New Zealand White specific-pathogen-free rabbits, fed cholesterol-free chow, were inoculated via the nasopharynx on three occasions, 2 weeks apart, with C. pneumoniae. Group I (n = 23) rabbits were untreated; group II (n = 24) rabbits were treated with azithromycin at 30 mg/kg of body weight daily for 3 days and then once every 6 days, starting 5 days after first inoculation and continuing until sacrifice (early treatment); and group III (n = 24) rabbits were treated with the same dose of azithromycin but initiated 2 weeks after the last inoculation. All animals were sacrificed at 10 to 11 weeks after initial inoculation and examined for signs of atherosclerosis of the aorta. Eight (34.8%) untreated rabbits developed early signs of atherosclerosis, whereas only one (4.2%) in the early-treatment group had such signs (P = 0.02). However, eight rabbits (33.3%) of the delayed-treatment group had atherosclerotic changes of the aorta and no significant reduction compared to untreated rabbits. Early treatment of C. pneumoniae-infected rabbits with azithromycin was highly effective (87%) in preventing atherosclerotic changes, but delayed treatment was ineffective. It is possible that longer or more aggressive antibiotic treatment may be needed to reverse preformed lesions or that antibiotics may not be of value once lesions have formed.

Animals↗