Impact of tobacco smoke exposure or indoor air pollution on nasopharyngeal bacteria in African infants in a birth cohort study

Abstract

Background: Bacterial nasopharyngeal (NP) carriage precedes the development of lower respiratory tract infection (LRTI), a leading cause of childhood illness. Exposure to indoor air pollution (IAP) or environmental tobacco smoke (ETS) may influence NP bacterial carriage. The impact of antenatal or postnatal IAP and ETS exposure on NP bacteria in infants was investigated. Methods: Mother-infant pairs enrolled in a South African birth cohort study were followed from birth through one-year. Immunizations included 13-valent pneumococcal conjugate vaccine and Haemophillus influenzae b . IAP exposures (particulate matter, nitrogen dioxide and volatile organic compounds) were measured at antenatal and postnatal home visits. Maternal and infant urine cotinine measured ETS exposure. NP swabs were taken at birth, 6 and 12 months for bacterial culture. Multivariate logistic regression investigated associations between NP organisms and IAP or ETS. Results: 986 infants contributed 2596 NP swabs; the predominant NP bacteria were Streptococcus pneumoniae (44%), Moraxella (34%), H. influenzae (27%) and Staphylococcus aureus (9%). Antenatal ETS was associated with increased S. pneumoniae at 6 months, OR1.62 (95%CI 1.10-2.37) and antenatal toluene with S. pneumoniae at 6 months, OR2.51 (95%CI 1.23-5.13) and H. influenzae at 12 months, OR2.27 (95%CI 1.24-4.16). Postnatal ETS was associated with S. pneumoniae at 6 months, OR1.46 (95%CI1.01-2.12) and H. influenzae at 12 months OR2.56 (95%CI1.21-5.41). Conclusion: Early-life environmental exposures are associated with increased prevalence of specific NP bacteria during infancy, which may predispose to the development of LRTI.