Streptococcus pneumoniae isolates in healthy children attending day-care centers in 12 states in Mexico

The aim of this study was to determine the prevalence of asymptomatic nasopharyngeal carriage of Streptococcus pneumoniae, which is a major factor in the transmission of this bacterium. Nasopharyngeal cultures were performed on children attending 32 day-care centers in 12 states in Mexico. Streptococcus pneumoniae was isolated from the nasopharynx of 829 out of 2,777(29.9%) subjects aged two months to six years. All children lived in urban areas and 80% spent more than six hours daily in a day-care center. Streptococcus pneumoniae serotypes most frequently identified were: 19F (23%), 6B (15.6%), 23F (11.2%) and 6A (14.9%). Thirty-six percent of the isolates were susceptible to penicillin. Serotype distribution suggests the possible benefits that could be obtained from the heptavalent pneumococcal conjugate vaccine.