Streptococcus pneumoniae Is Desiccation Tolerant and Infectious upon Rehydration

Streptococcus pneumoniae (pneumococcus) is a frequent colonizer of the nasopharynx and one of the leading causative agents of otitis media, pneumonia, and meningitis. The current literature asserts that S. pneumoniae is transmitted person to person via respiratory droplets; however, environmental surfaces (fomites) have been linked to the spread of other respiratory pathogens. Desiccation tolerance has been to shown to be essential for long-term survival on dry surfaces. This study investigated the survival and infectivity of S. pneumoniae following desiccation under ambient conditions. We recovered viable bacteria after all desiccation periods tested, ranging from 1 h to 4 weeks. Experiments conducted under nutrient limitation indicate that desiccation is a condition separate from starvation. Desiccation of an acapsular mutant and 15 different clinical isolates shows that S. pneumoniae desiccation tolerance is independent of the polysaccharide capsule and is a species-wide phenomenon, respectively. Experiments demonstrating that nondesiccated and desiccated S. pneumoniae strains colonize the nasopharynx at comparable levels, combined with their ability to survive long-term desiccation, suggest that fomites may serve as alternate sources of pneumococcal infection.