Transmission of Streptococcus pneumoniae in an urban slum community.

Background: Inhabitants of slum settlements represent a significant proportion of the population at risk for pneumococcal disease in developing countries.

Methods: We conducted a household survey of pneumococcal carriage among residents of a slum community in the city of Salvador, Brazil.

Results: Among 262 subjects, 95 (36%) were colonized with Streptococcus pneumoniae. Children <5 years of age (OR, 8.0; 95% CI, 3.5-18.6) and those who attended schools (OR, 2.7, 95% CI, 1.2-6.0) had significantly higher risk of being colonized. Of 94 isolates obtained from colonized individuals, 51% had serotypes included in the seven-valent pneumococcal conjugate vaccine. Overall, 10% (9 of 94 isolates) were nonsusceptible to penicillin and 28% (27 of 94 isolates) were resistant to cotrimoxazole. BOX-PCR, PFGE and MLST analyses found that 44% of the carriage isolates belonged to 14 distinct clonal groups. Strains of the same clonal group were isolated from multiple members of 9 out of the 39 study households. Nineteen carriage isolates had genotypes that were the same as those identified among 362 strains obtained from active surveillance for meningitis.

Conclusions: The study's findings indicate that there is significant intra- and inter-household spread of S. pneumoniae in the slum community setting. However, a limited number of clones encountered during carriage among slum residents were found to cause invasive disease.