Backgrounds:

Understanding streptococcal pneumoniae (Sp) carriage and transmission is fundamental to preventing invasive pneumococcal disease.

Microarray provides highly sensitive/specific serotype data, potentially useful in elucidating transmission pathways.

Methods

Across 10 UK-sites, 405 household family units (1378 participants; a unit = 2-year-old (index) child + 2+ household contacts) were enrolled as part of the Transmission of Pneumococcus Study. 5 serial nasopharyngeal samples (NPS) were collected 2-weekly over 2 months from each participant (October-December 2017 and 2018). LAIV was given to the index child on either day 0 or day 28.

Results:

At baseline, 274/405 index children were lytA positive and analysed by microarray.

240 samples were carrying Sp serotypes.

The four most common serotypes were 15B/C, 11A, 21 and 35F, present in 102 index participants (table 1).

71 of these index children had household contacts with lytA-positive samples. These were then also analysed by microarray (330 samples).

In 45/71 families, index children shared ≥1 serotypes with ≥1 household contacts. 43% of lytA NPS analysed had multiple serotype/strain carriage.

Table 1. The 4 most carried Sp serotypes (index, baseline)

Conclusions/Learning Points:

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

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

Further data analysis is investigating the role of Sp density in serotype commonality and Sp vs non-Sp streptococci.