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.

Early high dose antioxidant vitamins do not prevent bronchopulmonary dysplasia in premature baboons exposed to prolonged hyperoxia: a pilot study.

The antioxidant vitamins ascorbic acid (AA) and alpha-tocopherol (alpha-TP) effectively inhibit oxygen free radical-induced lipid peroxidation. Using a premature baboon model of hyperoxia-induced bronchopulmonary dysplasia (BPD), we measured concentrations of AA, alpha-TP, and conjugated dienes (CD, marker of lipid peroxidation) in four animals (hyperoxic antioxidant group) receiving high dose antioxidant vitamin supplementation (AA, 100 mg x kg x(-1) x d(-1); alpha-TP; 20 mg x kg x(-1) x d(-1)) and one animal receiving standard dose antioxidant vitamin supplementation (AA, 10 mg x kg x(-1) x d(-1); alpha-TP, 1 mg x kg x(-1) x d(-1)). Respiratory and histopathologic data were compared with data from 10 historical animals exposed to hyperoxia (hyperoxic control group) and 11 historical animals treated as required with oxygen (normoxic control group) who had received standard dose antioxidant vitamin supplementation. Compared with standard dose antioxidant vitamin supplementation, high dose antioxidant vitamin supplementation effectively raised AA concentrations in plasma (37 +/- 22 micromol/L and 395 +/- 216 micromol/L, respectively) and tracheal aspirates (62 +/- 35 micromol/L and 286 +/- 205 micromol/L, respectively), and alpha-TP concentrations in plasma (10.1 +/- 2.5 micromol/L and 24.6 +/- 17.5 micromol/L, respectively). However, there was no apparent effect on tracheal aspirate CD concentrations (482 +/- 333 micromol/L and 1050 +/- 1111 micromol/L, respectively), and respiratory parameters in the hyperoxic antioxidant group were comparable to those of the hyperoxic control group but significantly worse than in the normoxic control group. Finally, no protective effect of high dose antioxidant vitamin supplementation was noted at the histopathologic level.

Long-term partial liquid ventilation (PLV) with perflubron in the near-term baboon neonate.

PURPOSE: The feasibility and safety of continuous long-term (4-5 day) partial liquid ventilation (PLV) using perflubron was demonstrated in newborn baboons. PLV, a potential therapy for adult and neonatal respiratory distress syndrome (RDS), is conventional mechanical ventilation (CMV) with the lung filled to about functional residual capacity with perfluorochemical liquid. PROTOCOL: As a pilot trial for a larger preclinical study focused on the safety of extended duration PLV, three near term baboons were studied. The animals were delivered by cesarean section, anesthetized, intubated and placed on CMV. The animals were given intratracheal perflubron (30 ml/kg) and maintained on PLV for 96 hours. The transition back to gas ventilation occurred, after draining, over the fifth day (hrs 96-120). RESULTS: Two of the animals were born with normal pulmonary function, while the third developed respiratory distress prior to PLV. All the animals were adequately supported with PLV using moderate ventilator settings and low concentrations of oxygen. Perflubron distribution was enhanced by periodic rotation of the animals. Preliminary histology show vacuolated alveolar macrophages and no evidence of edema or other significant changes in the lungs. Pulmonary function in the RDS animal, after PLV treatment, showed normal gas exchange and lung mechanics. CONCLUSIONS: Three near term baboons, one with clinical RDS, tolerated 4 days of PLV followed by 1 day of CMV without complications using practical clinical management methods.

Toxic effects associated with the administration of deferoxamine in the premature baboon with hyaline membrane disease.

We hypothesized that administration of the iron chelator deferoxamine would inhibit iron-catalyzed free radical generation and lessen the severity of oxygen-induced pulmonary injury. To evaluate its efficacy and safety in premature infants, we administered deferoxamine by intravenous infusion to five premature baboons with hyaline membrane disease supported with conventional ventilation and 100% oxygen for 6 days. Seven animals served as controls. Deferoxamine treatment was initiated at 10 mg/kg per hour but, after the precipitous death of the first animal, was progressively reduced to 1.25 mg/kg per hour in the other animals. Four of five deferoxamine-treated baboons developed cardiovascular collapse and all five died by 42 hours. Five of the seven control animals survived the 6-day experimental period. Since cardiovascular toxic effects have not previously been reported, these findings suggest unique vulnerability of the immature cardiovascular system to iron chelation.

Prevention of nosocomial pneumonia using topical and parenteral antimicrobial agents.

The efficacy of antimicrobial agents applied topically in the oropharynx and trachea with and without intravenous antibiotics in preventing bacterial pneumonias during prolonged (7 to 10 days) mechanical ventilation was studied in 35 baboons, 30 of which had acute lung injury induced by either oleic acid or hyperoxia. In 12 animals receiving no antibiotics, only topical application of polymyxin B (PB), or only intravenous penicillin and gentamicin (IV PCN/GM), moderate or severe pneumonia was found in 81% of lobes examined at necropsy; no lobes were sterile. Pneumonias were polymicrobial in the absence of antibiotics, due to PCN-sensitive organisms in the topical PB group, and due to gram-negative bacilli in the IV PCN/GM group. Combinations of topical PB or GM or both plus IV PCN were highly efficacious in preventing pneumonia in 23 animals as only 15% of the lobes contained moderate to severe pneumonia and 52% of lobes were sterile. In these groups, histologically evident pneumonias were associated with low concentrations of bacteria in lung tissue, principally gram-negative bacilli resistant to the topical agent being used. Resistance to PB appeared to be solely due to selection of intrinsically resistant species, whereas resistance to GM may have developed through additional mechanisms as well. Although this approach to pneumonia prevention is clearly efficacious in this animal model, clinical studies are needed to define the frequency and significance of microbial resistance in human subjects.

Growth requirements of ferret tracheal epithelial cells in primary culture.

In mass cell culture conditions, protease dissociated ferret tracheal epithelial cells (FTE) proliferated in growth factor-supplemented F12 medium to high cell densities (0.5 X 10(5) cells/cm2) with an average population doubling time of 24 hr. The growth factor constituents of the F12 medium included epidermal growth factor (25 ng/ml), insulin (1 microgram/ml), transferrin (10 micrograms/ml), hydrocortisone (18 ng/ml), hypothalamus extract (30-100 micrograms/ml), and conditioned medium from mouse 3T3 fibroblasts. Growth of these cells under clonal conditions was achieved by the partial replacement of F12 medium with M199 medium which was attributed, in part, to the presence of vitamin A in M199 medium. Serum did not stimulate the growth of FTE cells. The epithelial cell nature of these cells in culture was confirmed by ultrastructural features and by immunofluorescent staining for fibronectin.