Site of Isolation Determines Biofilm Formation and 1 Virulence Phenotypes of Serotype 3 Streptococcus 2 pneumoniae Clinical Isolates 3 4

18 Streptococcus pneumonaie is a diverse species causing invasive as well as localized infections 19 that result in massive global morbidity and mortality. Strains vary markedly in pathogenic 20 potential, but the molecular basis is obscured by the diversity and plasticity of the 21 pneumococcal genome. In the present study, S. pneumoniae serotype 3 blood (n = 12) or ear 22 (n = 13) isolates were multi-locus sequence typed (MLST) and assessed for biofilm 23 formation and virulence phenotype. Blood and ear isolates exhibited similar MLST type 24 distribution, but differed markedly in phenotype. Blood isolates formed robust biofilms 25 only at pH 7.4, which was enhanced in Fe(III)-supplemented medium. Conversely, ear 26 isolates formed biofilms only at pH 6.8, and Fe(III) was inhibitory. Biofilm formation 27 paralleled luxS expression and genetic competence. In a mouse intranasal challenge model, 28 blood isolates did not stably colonize the nasopharynx, but spread to the blood; none 29 spread to the ear. Ear isolates colonized the nasopharynx at higher levels and also spread to 30 the ear compartment in a significant proportion of animals; none caused bacteremia. Thus, 31 pneumococci of the same serotype and MLST type exhibit distinct phenotypes in 32 accordance with clinical site of isolation, indicative of stable niche-adaptation within a 33 clonal lineage. 34 35 on O cber 8, 2017 by gest http/iai.asm .rg/ D ow nladed fom