High nasopharyngeal pneumococcal density, increased by viral coinfection, is associated with invasive pneumococcal pneumonia

Abstract

Background: We identified factors associated with pneumococcal colonization, high colonization density, and invasive pneumococcal pneumonia among patients hospitalized with acute lower respiratory tract infections (ALRTIs).

Methods: In 2010, 4025 cases were enrolled in surveillance in South Africa. A total of 969 of 4025 systematically selected nasopharyngeal-oropharyngeal specimens (24%) were tested for respiratory viruses and Streptococcus pneumoniae by real-time polymerase chain reaction. Of these, 749 (77%) had blood tested for S. pneumoniae.

Results: Pneumococcal colonization was detected in 55% of cases (534 of 969). On multivariable analysis that controlled for age and tuberculosis treatment, infection with influenza virus (adjusted odds ratio [OR], 2.2; 95% confidence interval [CI], 1.1-4.5), adenovirus (adjusted OR, 1.7; 95% CI, 1.1-2.7), rhinovirus (adjusted OR, 1.6; 95% CI, 1.1-2.3), and human immunodeficiency virus (HIV; adjusted OR, 1.6; 95% CI, 1.1-2.4) were associated with pneumococcal colonization. High colonization density was associated with respiratory virus coinfection (adjusted OR, 1.7; 95% CI, 1.1-2.6) and invasive pneumococcal pneumonia (adjusted OR, 2.3; 95% CI, 1.3-4.0), after adjustment for age and sex. Seven percent (52 of 749) had pneumococci detected in blood. On multivariable analysis among colonized cases, invasive pneumococcal pneumonia was associated with HIV (adjusted OR, 3.2; 95% CI, 1.4-7.5), influenza virus (adjusted OR, 8.2; 95% CI, 2.7-25.0), high colonization density (adjusted OR, 18.7; 95% CI, 2.3-155.1), and ≥5 days of hospitalization (adjusted OR, 3.7; 95% CI, 1.7-8.2).

Conclusions: Respiratory virus infection was associated with elevated colonization density and, in turn, invasive pneumococcal pneumonia.

Keywords: bacterial loads; colonization; invasive pneumococcal disease; pneumococcus; respiratory virus.