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Human rhinovirus (HRV) species C (HRV-C) have been associated with frequent and severe acute lower respiratory infections and asthma in hospitalized children. The prevalence of HRV-C among healthy children and whether this varies with ethnicity is unknown.

The polymorphisms of the important xenobiotic metabolizing enzymes CYP2D6, CYP2C19 and CYP2E1 have been studied extensively in a large number of populations and show significant heterogeneity in the frequency of different alleles/genotypes and in the prevalence of the extensive and poor metabolizer phenotypes. Understanding of inter-ethnic differences in genotypes is important in prediction of either beneficial or adverse effects from therapeutic agents and other xenobiotics. Since no data were available for Australian Aborigines, we investigated the frequencies of alleles and genotypes for CYP2D6, CYP2C19and CYP2E1in a population living in the far north of Western Australia. Because of its geographical isolation, this population can serve as a model to study the impact of evolutionary forces on the distribution of different alleles for xenobiotic metabolizing enzymes. Twelve CYP2D6alleles were analysed. The wild-type allele 1was the most frequent (85.8) and the non-functional alleles (4, 5, 16) had an overall frequency of less than 10. Only one subject (0.4) was a poor metabolizer for CYP2D6 because of the genotype 5/5. For CYP2C19, the frequencies of the 1(wild-type) and the non-functional (2and 3) alleles were 50.2, 35.5 and 14.3, respectively. The combined CYP2C19genotypes (2/2, 2/3or 3/3) correspond to a predicted frequency of 25.6 for the CYP2C19poor metabolizer phenotype. For CYP2E1, only one subject had the rare c2allele giving an overall allele frequency of 0.2. For CYP2D6and CYP2C19, allele frequencies and predicted phenotypes differed significantly from those for Caucasians but were similar to those for Orientals indicating a close relationship to East Asian populations. Differences between Aborigines and Orientals in allele frequencies for CYP2D610and CYP2E1 c2may have arisen through natural selection, or genetic drift, respectively.

The effect of inhaled bronchodilators in bronchiolitis has been difficult to evaluate due to problems with techniques for assessing respiratory function in infants. Two new techniques were used to assess the response to inhaled salbutamol in 17 infants with bronchiolitis. With one technique, expiratory flow, volume, and airway occlusion pressure were measured and used to derive compliance (Crs) and conductance (Grs) of the respiratory system from a passive expiration induced by a brief end-inspiratory airway occlusion. With the other technique, the maximum flow at functional residual capacity (VmaxFRC) was measured from a partial maximum expiratory flow-volume curve generated by external chest compression. For the group, there was no change in compliance or conductance after salbutamol, but salbutamol caused a fall in maximum flow at functional residual capacity (p< 0.01) and in the time constant of tidal expiration (p< 0.01). The decrease in maximum flow at functional residual capacity with salbutamol is consistent with increased airway collapse on forced expiration. The decrease in tidal time constant suggests that the drug decreases expiratory braking. Presence of such braking activity may be an important strategy for maintaining lung volume. In summary, salbutamol failed to produce a beneficial effect on airways in bronchiolitis, but did produce changes in expiration which may be harmful in some infants.