Meningococcal colonization and infection in children and their household contacts.

A bacteriologic survey was performed to estimate the prevalence and duration of meningococcal carriage in children in Montreal, Canada. Infants and children with proven meningococcal infection, or with asymptomatic meningococcal nasopharyngeal (NP) carriage, and their household contacts, were also studied to define communicability. N. meningitidis was present in 30 (2.4%) of the NP cultures from 1238 asymptomatic infants and children in this civilian population during a non-epidemic period. Meningococcal carriage was not found in 278 subjects 1--60 days of age; there was no difference in carriage rates between the sexes and between hospitalized and non-hospitalized children in all age groups. Meningococci were initially isolated from 11 of 106 household contacts of 29 ill index cases and from 15 of 104 contacts of 29 asymptomatic carriers; 35% of all contacts (index cases and carriers) were colonized by the eighth week of surveillance. Duration of NP carriage was longer (mean 15.2 weeks) in disease-free families than in families of ill patients (mean 5.5 weeks). Serogroups B and C were most commonly isolated from both ill and asymptomatic subjects. Resistance to sulfadiazine (MIC greater than or equal to mg/100 ml) was present in 6.5% and 39.4% of group B and group C strains, respectively. Although chemoprophylaxis was not used, there were no secondary cases among the 29 families of index cases.