Person-to-person transmission of Kingella kingae among day care center attendees

Fifty Kingella kingae organisms, isolated from tonsillar cultures of day ca re center attendees during an 11-month period, and 60 isolates derived from epidemiologically unrelated individuals, including 19 isolates from respir atory carriers and 41 isolates from patients with invasive infections, were typed by immunoblotting, pulsed-held gel electrophoresis, and ribotyping, One strain, defined by unique immunoblotting, pulsed-field gel electrophore sis, and ribotyping patterns, represented 14 day care isolates (28%) and wa s frequently isolated during the first half of the follow-up period; a seco nd strain represented 23 (46%) isolates and prevailed during the last 5 mon ths. Children frequently carried the same strain continuously or intermitte ntly for weeks or months, when it was replaced by a new strain. Epidemiolog ically unrelated organisms showed greater variability, and no strain repres ented >5% of isolates. The present results support person-to-person transmi ssion of K. kingae among young children in the day care setting.