Predictors of upper respiratory Streptococcus pneumoniae colonization among working-age adults with prevalent exposure to overcrowding

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Background The epidemiology of adult pneumococcal carriage remains poorly understood. We assessed risk factors for pneumococcal carriage among adults in socioeconomically-disadvantaged farmworker communities with prevalent overcrowding. Methods From July-November 2020, we administered surveys and collected saliva from working-age adults within clinical and community settings throughout Monterey County, California. We detected pneumococci via qPCR assays targeting lytA and piaB genes. We evaluated predictors of pneumococcal carriage detection via conditional logistic regression. Results Among 1,283 participants, 117 (9.1%) had any detectable pneumococcal carriage and 53 (4.1%) carried pneumococci at a higher density threshold ( lytA and piaB c T < 35). Pneumococcal carriage was more common among individuals of lower socioeconomic status, as signified by indigenous background (odds ratio [OR]=3.94 [95% confidence interval: 2.36-6.60]), engagement in fieldwork (OR=2.01 [1.12-3.63]), and lacking high school-level education (OR=0.48 [0.26-0.90]). Within the household, carriers were more likely than non-carriers to be exposed to children aged <5 years (OR=1.45 [0.95-2.20]), and to be exposed to crowding (OR=1.48 [0.96-2.30] and 2.84 [1.20-6.73], respectively, for participants living in households with >2-4 and >4 persons per bedroom vs. ≤2 persons per bedroom). Household crowding was independently associated with increased risk of carriage among participants not exposed to children aged <5 years (OR=2.05 [1.18-3.59] for participants living in households with >2 vs. ≤2 persons per bedroom). Exposure to children aged <5 years and exposure to household crowding were each associated with increased pneumococcal density among carriers ( piaB c T difference of 2.04 [0.36-3.73] and 2.44 [0.80-4.11], respectively). Conclusions While exposure to young children was an important risk factor for pneumococcal carriage, the association of crowding with increased risk of carriage in households without young children suggests transmission among adults may also occur in crowded congregate settings.