Background

Quantification of Streptococcus pneumoniae (Sp) carriage density and identification of serotypes in contacts contribute to understanding Sp transmission and thus evaluating pneumococcal conjugate vaccine impact.

Methods

266 lytA-positive nasopharyngeal samples (NPS) taken during season 1 (of 2, October-December 2017) of the Transmission of Pneumococcus (TOP) study (see abstract 715) were analysed by microarray. NPS were collected from 120 families, 2-weekly over 2 months.

Results

83/120 index children (2-year-olds) were lytA positive at baseline (visit 1): the three most common serotypes were 11A, 15B and 35F (n=83) (Graph 1).

In 17/28 families (28 index children, 45 contacts: 26 <16-year-olds and 19), index children shared ≥1 strain/serotype with ≥1 household contact.

40% (107/266) of lytA-positive NPS analysed had multiple serotypes/strains.

Sp was not detected in some lytA-positive samples but rather related streptococcal species, particularly from participants aged ≥5 years (Table 1).

Conclusions

NP carriage of the same Sp serotypes by multiple household members suggests that household Sp transmission occurs.

Multiple serotype carriage was observed in a significant proportion of participants.

Among young children, the age group most likely to transmit Sp, lytA was more predictive of true Sp infection than it was among older persons.