Differences in Bacterial Colonization and Mucosal Responses Between High and Low SES Children in Indonesia

Background: Increased nasopharyngeal carriage of pathogenic bacteria is found in low socioeconomic status (SES) settings. How SES affects local immune responses, important for controlling colonization, is currently unknown.

Objective: Examining bacterial colonization and cytokine response in the nasal mucosa of children from high and low SES.

Methods: Nasosorption samples were collected in October 2019 from 48 high SES and 50 low SES schoolchildren, in a cross-sectional study in Makassar, Indonesia. Twenty-five cytokines were measured in nasal fluid. Quantitative polymerase chain reaction was performed to determine carriage and density of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Staphylococcus aureus. Data were analyzed using multivariate regression.

Results: H. influenzae and S. pneumoniae densities were increased in low SES settings compared to the high SES settings (P = 0.006, P = 0.026), with 6 and 67 times higher median densities, respectively. Densities of H. influenzae and S. pneumoniae were positively associated with levels of IL-1beta and IL-6. After correcting for bacterial density, IL-6 levels were higher in colonized children from high SES than low SES for H. influenzae and S. pneumoniae (both P = 0.039).

Conclusion: Increased densities of H. influenzae and S. pneumoniae were observed in low SES children, whereas IL-6 levels associated with colonization were reduced in these children, indicating that immune responses to bacterial colonization were altered by SES.