Pneumococcal Colonization Exacerbated by Influenza-Like Illness

Pneumococcal colonization of airways is exacerbated by influenza-like illness (ILI) in older adults, and persists beyond ILI recovery, according to a study published in Clinical Infectious Diseases.

Pneumococcal disease is strongly associated with respiratory viral infections in older adults; however, the impact of viruses on Streptococcus pneumoniae carriage prevalence and load remains poorly understood. This prospective observation study investigated the effects of ILI on pneumococcal carriage in community-dwelling older adults.

In total, 232 adults aged 60 years or older with ILI and 194 age-matched control adults without ILI were included.

During the 2014 to 2015 influenza season, participants contacted the study center if they had fever (>37.8 C) and a sudden onset of cough, rhinorrhea, sore throat, headache, chest pain, or myalgia. Patients who reported ILI symptoms provided saliva samples within 72 hours of symptom onset, 2 to 3 weeks after symptom onset, and 7 to 9 weeks after symptom onset. Patients in the control group provided 2 saliva samples 2 to 3 weeks apart.

However, no individual respiratory viruses significantly contributed to pneumococcal abundances among carriers in the ILI group.

Results showed that pneumococcal abundances were persistently elevated in the ILI group compared with the control group; however, there was no difference in prevalence of pneumococcal carriage between groups.

Overall, 25% of patients with ILI (57/232) and 18% of patients in the control group (35/194) tested positive for pneumococcus at least once during the study. Pneumococcal absolute abundances were significantly higher at onset of ILI when compared with carriers in the control group (P <.01) and remained elevated after recovery from ILI (P <.05).

Exposure to young children was associated with pneumococcal carriage at any sampling event (odd ratio [OR], 2.71; 95% CI, 1.51-5.02; P <.001); this association remained significant after stratifying for antibiotic therapy (P <.05). Risk for pneumococcal carriage due to exposure to young children identifies at first sampling in both the ILI group (P <.05) and control group (P <.05).

Among asymptomatic patients in the control group, the presence of rhinovirus infection  also associates with pneumococcal carriage (OR, 4.23; 95% CI, 1.16-14.22; P <.05).

Persistent carriers had relative and absolute abundances that were 3-fold higher in participants in the ILI group compared with the control group. New carriage events that occurred 2 to 3 weeks after acute ILI displayed a 10-fold higher absolute (P <.01) and 8-fold higher relative (P <.05) pneumococcal abundance when compared with new carriage events among patients in the control group.

Limitations include differences in age and timing of sample collection between groups.

“Our findings not only unveil the dynamics of pneumococcal colonization in older adults during ILI, but also emphasize the importance of using molecular methods and saliva in studies on pneumococcal carriage in older age cohorts,” study authors concluded.

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