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

Background: 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.

Methods: 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, Burkholderia spp., Staphylococcus aureus and Streptococcus pneumoniae, were validated using qPCR in the population. Associations for bacterial prevalence with atopic phenotypes were investigated.

Results: Pooling the initial screen and validation subjects, S. aureus and S. pneumoniae had higher prevalence in long-term compared with short-term subjects (25.0% vs 8.1%, P = 0.012; and 76.8% vs 48.4%, P = 0.002). Those immigrants with nasal S. pneumoniae presence resided longer (average time 90.4 months) in Australia than immigrants without S. pneumoniae (52.7 months; P = 0.001). After adjusting for confounders, Chinese immigrants with S. pneumoniae carriage have a five-fold increased risk of doctor-diagnosed eczema (odds ratio, OR 5.36, 95% CI: 1.10-26.14; P = 0.038) compared to immigrants without S. pneumoniae carriage. There was a trend of S. pneumoniae abundance correlating with reduced host Toll-like receptor gene expression.

Conclusion: Our findings suggest that nasal S. pneumoniae may play a role in the development of allergic conditions in Chinese immigrants in a Western environment.