BACTERIAL INTERACTIONS IN THE HUMAN NASOPHARYNX: THE IMPACT OF HIV COINFECTION IN CHILDREN

Abstract

Bacterial disease is a leading cause of morbidity and mortality in children globally. Invasive bacterial disease occurs only after asymptomatic colonization by an invasive strain in the nasopharynx, which is influenced by bacterial interactions and host immune responses. Nasopharyngeal colonization is also a platform for bacteria to evolve and spread within populations. To explore the effects of immunity and interventions on bacterial interactions in the nasopharynx, I analyze nasopharyngeal colonization of three disease-causing bacteria, Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus, in a cohort of HIV infected and uninfected children. S. pneumoniae was associated with 30% less S. aureus colonization and 150% greater H. influenzae colonization. By controlling for immune response and considering only HIV infected individuals, both associations were strengthened. However, the consumption of prophylactic antibiotics was associated with colonization by antibiotic-resistant bacteria, suggesting that these effects were confounded by antibiotic use. When the interaction in HIV infected individuals was assessed using methicillin-resistant S. aureus, removing the confounding effect of antibiotic use in addition to prophylactic antibiotic consumption, S. pneumoniae was associated with 70% less S. aureus colonization. This effect was strongest in vaccine serotypes of S. pneumoniae and in colonization by new serotypes in hosts colonized previously by a different S. pneumoniae strain. These results suggest that bacterial interactions may be mediated by innate immune responses and nuance the role of interventions in the care of HIV infected children.