Detection of Pneumococcal Carriage in Asymptomatic Healthcare Workers

Healthcare workers are at increased risk of exposure to respiratory pathogens including Streptococcus pneumoniae (pneumococcus). While little asymptomatic carriage has been reported in young-to-middle-aged adults, this may be due to nonsensitive diagnostic methods. The aim of the current study was to investigate the rates of pneumococcal carriage in a large cohort of healthcare workers, using saliva as a respiratory specimen.

We evaluated pneumococcal carriage in convenience samples of saliva, self-collected from asymptomatic healthcare workers (Connecticut, USA) who were testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from 30 March to 11 June 2020. DNA extracted from the culture-enriched saliva was later tested using quantitative polymerase chain reaction for piaB, lytA, and serotype. Saliva samples were considered positive for pneumococcus when the piaB cycle threshold value was <40.

Study participants were 22-74 years old (mean age, 38.5 years), 75% female, 75% white, and with occupations including registered nurses (48%), medical doctors (23%), and patient care assistants (5%). Overall, 138 of 1241 samples (11%) from 86 of 392 individuals (21%) tested piaB positive at some point during the 4-month study period, with 28 (33%) colonized individuals positive at multiple time points. Carriers reflected the overall study population. No significant demographic characteristics were associated with detection of pneumococcus. Colonized individuals primarily carried serotypes 19F (25.6%) and 3 (12.8%).

During a period of mandatory masking, we identified a cumulative pneumococcal carriage prevalence of 21% among healthcare workers. This study highlights that healthcare workers may act as unrecognized reservoirs of pneumococcus in the population. Despite long-standing pediatric immunization programs, vaccine-targeted serotypes continue to be prevalent among the adult population.