Increased nasal Streptococcus pneumoniae presence in Western environment associated with allergic conditions in Chinese immigrants

<p><strong>Background:</strong> Chinese immigrants living in Australia experience increased allergic conditions: asthma, eczema, hay fever and wheeze. Recently we reported diminished innate cytokine responses in long-term immigrants, potentially increasing their pathogenic viral load and microbial carriage. We hypothesise that a Western environment changes the nasal microbiome profile, and this altered profile may be associated with the development of allergic conditions. In this cross-sectional study, we aimed to examine the loading of viral and microbial respiratory pathogens in the upper airway.</p> <p><strong>Methods: </strong> Adult Chinese immigrants were grouped depending on time spent in Australia: short-term (<6 years) or long-term (≥6 years). First, age- and gender-matched immigrants were selected for an initial screen using quantitative polymerase chain reaction (qPCR) micro-array panels. Then based on initial results the viruses, human parainfluenza 3 and rhinovirus, and the bacteria, <i>Burkholderia spp.</i>, <i>Staphylococcus aureus</i> and <i>Streptococcus pneumoniae</i>, were validated using qPCR in the population. Associations for bacterial prevalence with atopic phenotypes were investigated.</p> <p><strong>Results: </strong> Pooling the initial screen and validation subjects, <i>S. aureus</i> and <i>S. pneumoniae</i> had higher prevalence in long-term compared with short-term subjects (25.0% vs 8.1%, <i>P</i> = 0.012; and 76.8% vs 48.4%, <i>P</i> = 0.002). Those immigrants with nasal <i>S. pneumoniae</i> presence resided longer (average time 90.4 months) in Australia than immigrants without <i>S. pneumoniae</i> (52.7 months; <i>P</i> = 0.001). After adjusting for confounders, Chinese immigrants with <i>S. pneumoniae</i> carriage have a five-fold increased risk of doctor-diagnosed eczema (odds ratio, OR 5.36, 95% CI: 1.10-26.14; <i>P</i> = 0.038) compared to immigrants without <i>S. pneumoniae</i> carriage. There was a trend of <i>S. pneumoniae</i> abundance correlating with reduced host Toll-like receptor gene expression.</p> <p><strong>Conclusion: </strong> Our findings suggest that nasal <i>S. pneumoniae</i> may play a role in the development of allergic conditions in Chinese immigrants in a Western environment.</p>