These data reveal that phenotypic diversity among ST-1 GBS is mainly driven by small genetic changes rather than extensive recombination, thereby extending knowledge into how pathogens adapt to humans. Group B Streptococcus (GBS) is a common colonizer of humans that emerged in the 1970s as the leading cause of invasive bacterial disease in neonates and infants less than 3 mo of age ( 7). GBS is divided into 10 serotypes based on the carbohydrate composition of its sialic acid containing capsule, but gene content at the genomic level does not necessarily correlate with capsular serotype ( 8, 9). A seven-gene multilocus sequence typing (MLST) allows for the classification of the majority of GBS strains isolated from humans into five major clonal complexes (CCs) with a recent study by Da Cunha et al. showing that the major GBS CCs are primarily derived from a limited number of tetracycline-resistant clones, suggesting a key role of tetracycline resistance in GBS strain emergence ( 10, 11). CC-17 GBS strains have been particularly well studied given their role as the major cause of severe, invasive infant disease ( 10, 12). In contrast, serotype V strains cause a larger percentage of invasive disease in nonpregnant adults compared with neonates ( 13– 15). Importantly, rates of invasive GBS disease have been increasing during the past 25 y in nonpregnant adults, with a significant part of the rise resulting from serotype V GBS strains ( 15– 17).ĭespite the clear and increasing impact of serotype V strains, data are limited regarding molecular epidemiology of serotype V GBS causing invasive disease in nonpregnant adults ( 14, 15, 18). Only a few studies of serotype V strains have investigated the noncapsular genetic makeup of the strains, and those that have done so have included colonizing and invasive GBS strains isolated from infants or have not described the clinical origin of the tested strains ( 18, 19). Thus, we sought to analyze a large cohort of clinically well-defined, geographically distinct, and temporally disparate GBS isolates by using a whole-genome approach to elucidate the population structure of serotype V GBS causing invasive disease in nonpregnant adults.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |