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OBJECTIVE: To use data from a clinical trial of zanamivir, a new antiviral drug, to estimate the costs and effectiveness of alternative treatment strategies for a high-risk population in Australia visiting a physician for treatment of influenza or influenza-like illness within 36 hours of symptom onset. DESIGN AND SETTING: This was a modelling study using data from a randomised, double-blind, placebo-controlled trial with centres in Australia, New Zealand and South Africa. Cost data were taken from standard Australian sources. METHODS: Efficacy data from the clinical trial were used to populate a computer model designed to estimate the costs and health outcomes associated with alternative treatments for influenza and influenza-like illness. Only patients who consulted the physician within 36 hours of symptom onset were included in this trial. Cost data were used to translate the clinical data into treatment cost estimates. RESULTS: Treatment with zanamivir for this high risk population results in an incremental cost of $A14.20 per day of symptoms avoided in the base case. The cost per quality-adjusted life-year (QALY) gained is $A11,715. The results are sensitive to several parameter values, including the influenza-positive rate and the impact of zanamivir on days to alleviate symptoms and hospitalisation. CONCLUSIONS: Influenza is costly for the high risk population who seek physician treatment. Treatment with zanamivir for this population is cost effective based on an $A78,000 per QALY benchmark. Zanamivir could be cost saving if it reduces the hospitalisation rate.

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A methane-utilizing mixed culture isolated from activated sludge by selective enrichment at 45°C was found to consist of three interacting species: a methaneutilizing bacterium, a citrate-utilizing bacterium, and a methanol-utilizing bacterium. All three species grew well at 45°C. Three different stable mixed cultures were reconstituted by various combinations of these pure cultures. The nutritional requirements and substrate ranges for each pure culture were determined. The nutritional requirements and substrate ranges for each pure culture were determined. The saturation constant for the methane-utilizing bacterium on methane (K CH 4) and for the methanol-utilizing bacterium on methanol (K CH 3OH) were 1.73 × 10-6 M and 4.51 × 10-7 M, respectively. The volumetric mass transfer coefficient for methane (KL a) was determined to be 65.6 hr-1 .

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A two-member methane-utilizing mixed culture of bacteria, formed by combining two pure cultures isolated from a naturally occurring methane-utilizing mixed culture, was studied in continuous culture. From the nutritional requirements and substrate ranges of the pure cultures, a mechanism for the interspecific interactions occurring in the mixed culture was proposed. Product formation kinetics were determined in continuous culture for each product involved in the proposed mechanism. From this proposed mechanism a mathematical model was derived based on simple material balance equations around a single-stage chemostat. The steady-state predictions of this model were compared to experimental results obtained from continuous-culture experiments with the two-member methane-utilizing mixed culture. Interspecific interactions occurring in two-member methanol-utilizing and three-member methane-utilizing mixed cultures have also been discussed.