Figure 1. Analysis of NTHi strain collections to ascertain the proportion of isolates containing phase variable modA alleles.

(a–d) Presents the four separate strain collections that were analysed to ascertain the distribution of phase variable modA alleles in NTHi populations; (a) collection containing a broad selection of NTHi isolates from a variety of sources (for example, culture collections, OM-prone individuals)⁶; (b) samples of paired isolates of NTHi isolated from patients presenting with chronic/recurrent OM¹⁷; (c) sample collection of NTHi isolates taken from OM-prone individuals¹⁸; (d) NTHi isolates from the nasopharynx of healthy children (collected as part of this study); and (e) the five modA alleles most commonly associated with OM—modA2, modA4, modA5, modA9 and modA10. Each modA gene is represented as a white arrow, with the DRD represented by a coloured box that matches the colour in panels a–d. The black box to the right of each gene represents the 5′ region of the downstream gene (an inactive restriction endonuclease). The blue arrow to the left of each modA gene represents the 3′ end of the gene upstream of each modA (in all the cases, a ribonuclease, rnhB). Details of the strain collections used in c and d are presented in Supplementary Table 1.