Elevated cytokine and chemokine levels and prolonged pulmonary airflow resistance in a murine Mycoplasma pneumoniae pneumonia model: a microbiologic, histologic, immunologic, and respiratory plethysmographic profile

Because Mycoplasma pneumoniae is hypothesized to play an important role in reactive airway disease/asthma, a comprehensive murine model of M. pneumoniae lower respiratory infection was established. BALB/c mice were intranasally inoculated once with M. pneumoniae and sacrificed at 0 to 42 days postinoculation. All mice became infected and developed histologic evidence of acute pulmonary inflammation, which cleared by 28 days postinoculation. By contrast, M. pneumoniae persisted in the respiratory tract for the entire 42 days studied. Tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), KC (functional IL-8), MIP-1alpha, and MCP-1/JE concentrations were significantly elevated in bronchoalveolar lavage samples, whereas IL-4 and IL-10 concentrations were not significantly elevated. Pulmonary airflow resistance, as measured by plethysmography, was detected 1 day postinoculation and persisted even after pulmonary inflammation had resolved at day 28. Serum anti-M. pneumoniae immunoglobulin G titers were positive in all mice by 35 days. This mouse model provides a means to investigate the immunopathogenesis of M. pneumoniae infection and its possible role in reactive airway disease/asthma.

The impact of steroids given with macrolide therapy on experimental Mycoplasma pneumoniae respiratory infection

BACKGROUND

Systemic steroids have been advocated in addition to antimicrobial therapy for severe Mycoplasma pneumoniae pneumonia. We evaluated the efficacy of clarithromycin, dexamethasone, and combination therapy for M. pneumoniae respiratory infection.

METHODS

Mice infected with M. pneumoniae were treated with clarithromycin, dexamethasone, combined clarithromycin/dexamethasone, or placebo daily; mice were evaluated at baseline and after 1, 3, and 6 days of therapy. Outcome variables included M. pneumoniae culture, lung histopathologic score (HPS), and bronchoalveolar lavage cytokine, chemokine, and growth factor concentrations.

RESULTS

Clarithromycin monotherapy resulted in the greatest reductions in M. pneumoniae concentrations. After 3 days of treatment, combination therapy significantly reduced lung HPS compared with placebo, clarithromycin, and dexamethasone alone, whereas, after 6 days of therapy, clarithromycin alone and combination therapy significantly reduced lung HPS compared with placebo. Concentrations of interleukin (IL)-12 p40, RANTES, macrophage chemotactic protein-1, and cytokine-induced neutrophil chemoattractant were significantly lower in mice treated with clarithromycin alone and/or combination therapy compared with dexamethasone alone and/or placebo; combination therapy resulted in a significantly greater reduction than clarithromycin alone for IL-12 p40 and RANTES.

CONCLUSIONS

Although monotherapy with clarithromycin had the greatest effect on reducing concentrations of M. pneumoniae, combination therapy had the greatest effect on decreasing levels of cytokines and chemokines as well as pulmonary histologic inflammation.

Fatal outcomes in family transmission of Mycoplasma pneumoniae

BACKGROUND

Mycoplasma pneumoniae continues to be a significant cause of community-acquired pneumonia and, on rare occasions, manifests as fulminant disease that leads to mortality, even in healthy individuals.

METHODS

We conducted a retrospective study on members of a family who were quarantined by the Centers for Disease Control and Prevention in 2002 for respiratory failure and death of a 15-year-old brother (sibling 1) and a 13-year-old sister (sibling 2). Collected airway, cerebrospinal fluid (CSF), and serum samples from both deceased siblings and serum samples from both parents and the remaining 3 ill siblings (sibling 3-5) were tested using a range of diagnostic assays. Autopsy lung tissue samples from sibling 2 were also assessed using immunohistochemical and immunoelectron microscopic methods.

RESULTS

Autopsy evaluation of sibling 1 revealed cerebral edema consistent with hypoxic ischemic encepatholopathy and pulmonary findings of bronchiolitis obliterans with organizing pneumonia (BOOP). Postmortem lung examination of sibling 2 revealed lymphoplasmacytic bronchiolitis with intraluminal purulent exudate, BOOP, and pulmonary edema. Results of diagnostic assays implicated the household transmission of M. pneumoniae among all 5 siblings and both parents. Further analysis of lung tissue from sibling 2 demonstrated the presence of M. pneumoniae organisms and community-acquired respiratory distress syndrome toxin. M. pneumoniae was cultured directly from sibling 2 autopsy lung tissue.

CONCLUSION

Evidence is provided that M. pneumoniae was readily transmitted to all members of the household and that the resulting infections led to a spectrum of individual responses with variation in disease progression, including lymphoplasmacytic bronchiolitis, BOOP, and death.

Respiratory tract infection with Mycoplasma pneumoniae in interleukin-12 knockout mice results in improved bacterial clearance and reduced pulmonary inflammation

Mycoplasma pneumoniae is a leading cause of pneumonia and is associated with asthma. Evidence links M. pneumoniae respiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices of M. pneumoniae pneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 in M. pneumoniae respiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 10(7) CFU of M. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected with M. pneumoniae were found to have significantly lower BAL M. pneumoniae concentrations compared with M. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-gamma than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P = 0.065) and TNF-alpha (P = 0.078). No differences were found for IL-1beta, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimental M. pneumoniae pneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.

Pharmacodynamics and bactericidal activity of moxifloxacin in experimental Escherichia coli meningitis

Moxifloxacin, an 8-methoxyquinolone with broad-spectrum activity in vitro, was studied in the rabbit model of Escherichia coli meningitis. The purposes of this study were to evaluate the bactericidal effectiveness and the pharmacodynamic profile of moxifloxacin in cerebrospinal fluid (CSF) and to compare the bactericidal activity with that of ceftriaxone and meropenem therapy. After induction of meningitis, animals were given single doses of 10, 20, and 40 mg/kg or divided-dose regimens of 5, 10, and 20 mg/kg twice, separated by 6 h. After single doses, the penetration of moxifloxacin into purulent CSF, measured as percentage of the area under the concentration-time curve (AUC) in CSF relative to the AUC in plasma, was approximately 50%. After single doses of 10, 20, and 40 mg/kg, the maximum CSF concentration (C(max)) values were 1.8, 4.2, and 4.9 microg/ml, respectively; the AUC values (total drug) were 13.4, 25.4, and 27.1 microg/ml x h, respectively, and the half-life values (t(1/2)) were 6.7, 6.6, and 4.7 h, respectively. The bacterial killing in CSF for moxifloxacin, calculated as the Deltalog(10) CFU per milliliter per hour, at 3, 6, and 12 h after single doses of 10, 20, and 40 mg/kg were -5.70, -6.62, and -7.02; -7.37, -7.37, and -6.87; and -6.62, -6.62, and -6.62, respectively, whereas those of ceftriaxone and meropenem were -4.18, -5.24, and -4.43, and -3.64, -3.59, and -4.12, respectively. The CSF pharmacodynamic indices of AUC/MBC and C(max)/MBC were interrelated (r = 0.81); there was less correlation with T > MBC (r = 0.74). In this model, therapy with moxifloxacin appears to be at least as effective as ceftriaxone and more effective than meropenem therapy in eradicating E. coli from CSF.

BMS-284756 in experimental cephalosporin-resistant pneumococcal meningitis

BMS-284756 is a novel des-fluoro(6) quinolone with a broad antimicrobial activity, including Streptococcus pneumoniae. The purpose of this study was to evaluate the pharmacodynamic profile and effectiveness of BMS-284756 for therapy of experimental meningitis caused by penicillin- and cephalosporin-resistant S. pneumoniae (CRSP). Meningitis was induced in rabbits by intracisternal inoculation of CRSP. BMS-284756 was given intravenously 16 h after intracisternal inoculation in single doses of 2.5 (n = 5 animals), 5 (n = 6), 10 (n = 6), 20 (n = 8), and 30 mg/kg (n = 6), in two doses of 10 mg/kg each separated by 5 h (n = 4), and as a 20-mg/kg dose followed 5 h later by 10 mg/kg (n = 5). The MICs and MBCs of BMS-284756, ceftriaxone, and vancomycin were 0.06 and 0.06, 4 and 4, and 0.25 and 0.25 microg/ml, respectively. After single doses of 10, 20, and 30 mg/kg, the maximum concentrations in cerebrospinal fluid (CSF) (mean +/- standard deviation) were 0.32 +/- 0.12, 0.81 +/- 0.38, and 1.08 +/- 0.43 microg/ml, respectively; the elimination half-life in CSF was 4.5 to 6.3 h. The CSF bacterial killing rates (BKR) at 5 h of the single-dose regimens of 10, 20 and 30 mg/kg were -0.84 +/- 0.48, -1.09 +/- 0.32, and -1.35 +/- 0.05 Deltalog(10) CFU/ml/h. The BKR(0-5) of the divided regimens (10 mg/kg twice and 20 mg/kg followed by 10 mg/kg) was -0.82 +/- 0.52 and -1.24 +/- 0.34 Deltalog(10) CFU/ml/h, respectively. The BKR(0-5) of the combined therapy with vancomycin and ceftriaxone was -1.09 +/- 0.39 Deltalog(10) CFU/ml/h. The penetration of BMS-284756 into purulent CSF relative to plasma was 14 to 25%. The bactericidal effect of BMS-284756 in CSF was concentration dependent. BMS-284756 at 30 mg/kg as a single or divided dose was as effective as standard therapy with vancomycin and ceftriaxone.

Efficacy of increasing dosages of clarithromycin for treatment of experimental Mycoplasma pneumoniae pneumonia

OBJECTIVES

Mycoplasma pneumoniae respiratory infection is a common cause of acute respiratory infection in children and adults. We evaluated the efficacy of increasing dosages of clarithromycin for the optimized therapy of M. pneumoniae respiratory infection in a mouse model.

METHODS

BALB/c mice were intranasally inoculated once with M. pneumoniae or SP4 broth (control). Groups of mice were treated with increasing dosages of clarithromycin (10, 25 or 75 mg/kg/day) or placebo subcutaneously daily. Groups of mice were evaluated after 1, 2, 3, 6 and 12 days of therapy. Outcome variables included quantitative M. pneumoniae culture, histopathological score of the lungs, bronchoalveolar lavage (BAL) cytokine/chemokine/growth factor concentrations and plethysmography after aerosolized methacholine to assess airway hyperresponsiveness.

RESULTS

Elevated dosages of clarithromycin resulted in greater antimicrobial efficacy with significantly reduced M. pneumoniae quantitative cultures (P < 0.05), as well as greater improvement in markers of disease severity with significantly reduced lung histopathology scores, BAL cytokine concentrations and airway hyperresponsiveness (P < 0.05).

CONCLUSIONS

Escalated dosing of clarithromycin resulted in significantly greater therapeutic efficacy in the treatment of experimental M. pneumoniae respiratory infection.