868. Relevance of Capsular Polysaccharide and Pilus Protein Expression to Design of Group B Streptococcal (GBS) Vaccines for Adults
Session: Poster Abstract Session: Bacterial Infections: Pathogenesis and Immunity
Friday, October 9, 2015
Room: Poster Hall
Background:  In 2013, there were 28,500 reported cases of invasive GBS disease in the US; 93% were in adults.  Capsular polysaccharides (CPS) and pilus proteins are protective surface-associated GBS virulence factors but their expression in blood isolates from adults is unknown.  We aimed to define clinical features and expression of CPS and pilus proteins in a large cohort of adults with invasive GBS infection.

Methods:  Prospective, laboratory-based surveillance from 7 Houston hospitals (between 3/2012 and 10/2014) identified adults with GBS bacteremia.  Demographic and clinical information were collected from consenting patients.  Capsular typing of blood isolates was performed by capillary precipitin and FACS analysis and genotype by multiplex PCR.  Pilus island (PI) expression was determined by FACS and pilus gene analysis by PCR.

Results:  102 adults were enrolled.  Their mean age was 59 years (25-91). 59% were male; 45% were white, 30% black and 25% Hispanic.  All had at least one underlying condition, including diabetes mellitus (58%), renal insufficiency/end stage renal disease (20%), cirrhosis/hepatic failure (17%) or other (5%).  Clinical syndromes included cellulitis (38%), bacteremia without focus (17%), osteomyelitis/arthritis (14%), abscess (10%) and endocarditis/endovascular infection (9%).  CPS type Ia predominated (24% of isolates), followed by III (16%), IV (14%), V (12%), Ib (12%), and II (9%). 14% of strains did not express CPS, including 4 type II and 7 type V strains.  Most strains (55%) carried PI-1+PI-2a and 33% only PI-2a (23/34 were type Ia).  91%of isolates expressed at least one pilus type; most expressed PI-2a alone (44%) or with PI-1 (23%).  PI-2b was expressed only by types III and IV (12%). Genes for PI-1+PI-2a were present in most (8/11) of the 11% of isolates not expressing pilus proteins.  All GBS strains expressed CPS, PI or both.

Conclusion:  Invasive GBS infection in adults is clinically diverse.  More strains than previously reported did not express CPS and type IV has emerged as a substantial cause of disease.  A subset did not express CPS (14%) or pilus proteins (11%) but all expressed one of these, suggesting that candidate GBS glycoconjugate vaccines for adults should incorporate each of these potentially protective antigens.

Morven Edwards, MD, FIDSA, FPIDS1, Marcia Rench, BSN1, C. Daniela Rinaudo, PhD2, Monica Fabbrini, PhD2, Giovanna Tuscano, PhD2, Carol J. Baker, MD, FIDSA, FSHEA, FPIDS1 and Immaculada Margarit, PhD2, (1)Pediatrics, Baylor College of Medicine, Houston, TX, (2)Novartis Vaccines and Diagnostics S.r.l. (A GSK Company), Siena, Italy


M. Edwards, None

M. Rench, None

C. D. Rinaudo, None

M. Fabbrini, None

G. Tuscano, None

C. J. Baker, None

I. Margarit, None

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