Risk factors associated with nasopharyngeal carriage and density of , , , and in young children living in Indonesia.

Background: Potentially pathogenic bacteria , , , and are commonly carried in the nasopharynx of young children. Host and environmental factors have been linked with pathogen carriage, and in many studies rural children have higher carriage rates than their urban counterparts. There are few published data on what factors contribute to increased pathogen density. The objectives of this study were to identify risk factors for nasopharyngeal carriage and density of , , , and in young children in Indonesia.

Methods: Risk factor analysis was done using data on bacterial carriage and participant characteristics from a cross-sectional study that enrolled 302 children aged 12-24 months living in urban or semi-rural areas of Indonesia. Associations between host factors and odds of pathogen carriage were explored using logistic regression. Characteristics identified to be independent predictors of carriage by univariable analysis, as well as those that differed between urban and semi-rural participants, were included in multivariable models. Risk factors for increased pathogen density were identified using linear regression analysis.

Results: No differences in carriage prevalence between urban and semi-rural children were observed. Multiple children under the age of 5 years in the household (< 5y) and upper respiratory tract infection (URTI) symptoms were associated with carriage, with adjusted odds ratios (aOR) of 2.17 (95% CI 1.13, 4.12) and 2.28 (95% CI 1.15, 4.50), respectively. There was some evidence that URTI symptoms (aOR 1.94 [95% CI 1.00, 3.75]) were associated with carriage of . Children with URTI symptoms ( = 0.002), and low parental income ( = 0.011) had higher density, whereas older age was associated with lower density ( = 0.009). URTI symptoms were also associated with higher density ( = 0.035). Low maternal education ( = 0.039) and multiple children < 5y ( = 0.021) were positively associated with density, and semi-rural residence was associated with higher density ( < 0.001).

Conclusions: This study provides a detailed assessment of risk factors associated with carriage of clinically-relevant bacteria in Indonesian children, and new data on host factors associated with pathogen density.