Background. Bacterial pneumonia and otitis media often follow influenza and other upper respiratory viral infections. Streptococcus pneumoniae (SP) is one of the most frequent culprits. While animal models suggest influenza enhances SP transmission and growth and that SP may increase influenza morbidity, there is limited evidence in human populations. We estimated the prevalence of SP among adults and children with acute respiratory illness (ARI) with and without laboratory confirmed influenza, to gain insight into the interaction between SP and influenza.
Methods. The Household Influenza Vaccine Effectiveness (HIVE) Study actively monitored ARI among 290 households with at least 2 children during the 2013-2014 influenza season. In addition to clinical data and specimens collected for viral testing, HIVE participants 2 years-old and older with ARI from 166 households provided oropharyngeal swabs for bacterial studies. Samples were screened by real-time PCR (RT-PCR) for the presence of influenza and 10 other respiratory viruses, and, in a blinded way, for the presence and relative abundance of SP by RT-PCR amplifying the lytA gene. SP serotypes were determined using multiplex PCR.
Results. 332 subjects reported illness at least once, for a total of 519 illnesses. SP was found in the oropharynx of 118 different subjects (35.5%), corresponding to 148 illnesses (28.5%): 34/241 (14%) in adults and 114/278 (41%) in children (p < 0.001). Subjects carrying SP were younger (on average 13.8 years-old vs 25.2, p < 0.001), and were more commonly infected with influenza (8.7% vs 5.9%, p = 0.24) than subjects without SP, although not significantly. This was particularly true for children under 17 (9% of SP carriers had influenza, vs 4.7% of non-carriers, p = 0.10). Relative abundance of SP was higher in SP carrying children than adults (p < 0.001), but did not differ by influenza infection. Results of other respiratory viruses and serotypes are pending.
Conclusion. SP oropharyngeal colonization was frequent in a household population with members suffering from ARI. Colonization rates and relative abundance of SP were higher in children. We found a tendency towards a higher rate of SP carriage among subjects with influenza, especially in the children, suggesting an association between SP colonization and viral infection.