Joseph W. St. Geme, III, MD

faculty photo
Professor of Pediatrics (Infectious Diseases)
Attending Physician, Pediatric Infectious Diseases, General Pediatrics, The Children's Hospital of Philadelphia
Leonard & Madlyn Abramson Endowed Chair in Pediatrics , The Children's Hospital of Philadelphia
Department: Pediatrics
Graduate Group Affiliations

Contact information
The Children’s Hospital of Philadelphia
Physician-in-Chief Suite, Room 9NW67
34th St. and Civic Center Blvd.
Philadelphia, PA 19104

1205D Abramson Research Center
3615 Civic Center Blvd.
Philadelphia, PA 19104
Philadelphia, PA 19104-4399
Office: 215-590-2766
Lab: 267-426-8374
Stanford University, Stanford, CA, 1979.
M.D. (Medicine)
Harvard Medical School, Boston, MA, 1984.
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Description of Research Expertise

The St. Geme laboratory is interested in understanding the molecular and cellular determinants of bacterial pathogenicity, with a particular focus on Haemophilus influenzae and Kingella kingae. H. influenzae is a common commensal in the nasopharynx and represents the leading cause of otitis media and sinusitis in children and exacerbations of chronic obstructive pulmonary disease in adults. K. kingae is a common commensal in the posterior pharynx and has emerged as a major cause of bone and joint infections in young children. We are using a combination of genetic methods, protein chemistry, X-ray crystallography, high-resolution microscopy, and animal models to study H. influenzae and K. kingae as model mucosal pathogens, aiming to understand how these organisms: 1) initiate infection; 2) establish a state of commensalism; and 3) transition from a state of commensalism to produce disease.

Shipping Address

The CHOP Research Institute
Attn: Joseph W. St. Geme
Lab 1205D Abramson Research Center
3615 Civic Center Blvd
Philadelphia, PA 19104

Description of Research

Adherence to host tissue is an important first step in the process of bacterial colonization and the pathogenesis of bacterial disease, and a detailed understanding of the determinants of adherence may lead to medical interventions aimed at preventing disease. The St. Geme lab investigates the molecular determinants of adherence by nontypeable (nonencapsulated) Haemophilus influenzae and Kingella kingae, two common pediatric pathogens.

1. H. influenzae

Nontypeable H. influenzae is a common cause of otitis media and sinusitis in children and is also an important etiology of exacerbations of underlying lung disease, such as cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease. Isolates of nontypeable H. influenzae express a variety of adhesive proteins that interact with the host respiratory epithelium and facilitate the process of colonization. Examples under study in the St. Geme lab include HMW1, HMW2, Hia, and Hap, all of which are transported to the bacterial surface via the type V secretion system as either members of a two-partner secretion system or autotransporters.

HMW1 and HMW2 are highly homologous glycoproteins that are prototypic members of a two-partner secretion system and are translocated across the outer membrane by cognate outer membrane proteins called HMW1B and HMW2B, respectively. The HMW1 and HMW2 adhesins form short helical fibers on the bacterial surface and facilitate high levels of adherence to cultured human respiratory epithelial cells. HMW1 and HMW2 have another partner involved in their maturation, a glycosyltransferase encoded by the hmw1C or hmw2C gene. HMW1 and HMW2 are modified in the cytoplasm with monosaccharides and disaccharides at multiple sites and are then transported into the periplasm by the Sec secretion system. In the periplasm the N-terminal TPS domain targets HMW1 and HMW2 to HMW1B and HMW2B, facilitating translocation across the outer membrane and localization on the bacterial surface. In ongoing research we are investigating the recognition between HMW1 and HMW1B and between HMW2 and HMW2B, the mechanism of HMW1 and HMW2 tethering to the bacterial surface, the purpose of glycosylation of HMW1 and HMW2, and the conservation of HMW1C-like glycosyltransferases in other gram-negative bacteria. We are also examining the immunologic properties and the vaccine potential of HMW1 and HMW2.

The Hia adhesin is a trimeric autotransporter and is present in approximately 25% of nontypable H. influenzae strains, including almost all H. influenzae strains that lack HMW1 and HMW2 adhesins. Like other trimeric autotransporters, Hia has an N-terminal signal peptide, an internal passenger domain, and a C-terminal translocator domain (also designated a -domain) and folds into a trimeric structure with three identical faces. The Hia passenger domain harbors two homologous binding domains referred to as HiaBD1 and HiaBD2 and mediates high affinity adherence to human respiratory epithelial cells. The presence of three identical faces provides potential for three identical binding pockets and a multivalent interaction with the host cell surface, resulting in increased avidity and more stable interaction compared with a monovalent interaction. This increase in avidity may be especially important in allowing organisms to overcome mechanical forces in the host, including the mucociliary escalator, coughing, and sneezing. Beyond facilitating multivalent binding, a trimeric architecture may also confer stability to proteases and detergents. In ongoing research, we are investigating the Hia host cell receptor and are examining the relationship between Hia-mediated adherence and epithelial cell cytokine production.

Hap is a conventional autotransporter protein and has an N-terminal signal peptide, an internal passenger domain, and a C-terminal translocator domain in a monomeric architecture. This protein was first identified based on its capacity to promote bacterial adherence and entry in assays with cultured human epithelial cells. In addition, Hap mediates bacterial adherence to extracellular matrix proteins and bacterial aggregation and microcolony formation. The C-terminal 511 amino acids of the Hap passenger domain are responsible for interactions with fibronectin, laminin, and collagen IV, and the C-terminal 311 amino acids of the Hap passenger domain are responsible for interactions with epithelial cells and for mediating Hap-Hap interaction, triggering bacterial aggregation and microcolony formation. Hap also contains an N-terminal serine protease domain, with a canonical chymotrypsin family catalytic triad including His98, Asp140, and Ser243. The serine protease domain mediates autoproteolysis and release of the Hap passenger domain from the bacterial surface, modulating bacterial adherence and aggregation. Autoproteolytic activity is inhibited by secretory leukocyte inhibitor (SLPI), a serine protease inhibitor that is present in varying amounts in the upper and lower respiratory tract and that results in enhanced Hap adhesive activity. In ongoing work, we are examining the relationship between Hap-mediated microcolony formation and biofilm formation, the mechanism by which lipopolysaccharide biosynthesis affects Hap stability in the outer membrane, and the influence of Hap on HMW1- and HMW2-mediated adherence.

2. Kingella kingae

Kingella kingae is an emerging pediatric pathogen that is being recognized increasingly as a cause of septic arthritis, osteomyelitis, and bacteremia in young children. The St. Geme lab is currently studying the interplay between three surface factors that influence K. kingae adherence to host tissue, namely, type IV pili, a trimeric autotransporter called Knh, and a polysaccharide capsule. Using genetic, biochemical, cell biological, and microscopy approaches, we have established that type IV pili mediate the initial interaction with the host cell surface and then undergo retraction, drawing the organism closer to the host cell and displacing the polysaccharide capsule. Displacement of the capsule exposes Knh, allowing Knh to interact with an as yet unknown host cell receptor. In additional work, we are characterizing the structural and antigenic heterogeneity and the functional properties of the K. kingae polysaccharide capsule. There are a total of 4 different K. kingae polysaccharide capsules, designated types a-d. The type a and type b capsules account for over 95% of invasive isolates. Assays with normal human serum and human neutrophils have demonstrated that the polysaccharide capsule mediates serum resistance and interferes with neutrophil killing. In additional work, we have identified an exopolysaccharide that also mediates serum resistance and blocks neutrophil killing. There are at least 2 structurally distinct exopolysaccharides, designated type 1 and type 2.

We are using an infant rat model of invasive disease to examine the contribution of a variety of putative virulence factors to K. kingae virulence.

Lab Personnel:
• Eric Porsch – Research Associate II
• Nina Montoya – Graduate Student
• Nadia Kadry – Graduate Student
• Alexandra Perry – Graduate Student

Personnel at Duke:
• Sue Grass – Research Associate

Selected Publications

Muñoz VL, Porsch EA, St. Geme JW 3rd: Kingella kingae surface polysaccharides promote resistance to neutrophil phagocytosis and killing. mBio 10(3): e00631-19, June 2019 Notes: doi: 10.1128.

Muñoz VL, Porsch EA, St. Geme JW 3rd: Kingella kingae surface polysaccharides promote resistance to human serum and virulence in a juvenile rat model. Infect Immun 22(6): e00100-18, May 2018 Notes: doi: 10.1128/IAI.00100-18.

Kern B, Porsch EA, St. Geme JW 3rd: Defining the mechanical determinants of Kingella kingae adherence to host cells. J Bacteriol 199: e00314-17, 2017.

Porsch EA, Starr K, Yagupsky P, St. Geme JW 3rd: The type a and type b polysaccharides capsules predominate in an international collection of invasive Kingella kingae isolates. mSphere 2(2): e00060-17, 2017.

Starr F, Porsch EA, Seed PC, Heiss C, Naran R, Forsberg LS, Amit U, Yagupsky P, Azadi P, St. Geme JW 3rd: Kingella kingae expresses four structurally distinct polysaccharide capsules that differ in their correlation with invasive disease. PLoS Pathogens 12(10), 2016 Notes: e1005944.

Rempe KA, Porsch EA, Wilson J, St. Geme JW 3rd: The Haemophilus influenzae HMW1 and HMW2 adhesins promote upper respiratory tract colonization in rhesus macaque monkeys. Infect Immun 84: 2771-2778, 2016.

Starr KF, Porsch EA, Seed PC, and St. Geme JWIII. : Genetic and molecular basis of Kingella kingae encapsulation. Infection and Immunity. 84: 1775-1784, 2016.

McCann JR, Mason SN, Auten RW, St. Geme JWIII, Seed PC.: Early life intranasal colonization with nontypeable Haemophilus influenzae exacerbates juvenile airways disease in mice. Infection and Immunity. 84: 2022-2030, 2016.

Grass S, Rempe KA, St. Geme JWIII. : Structural determinants of the interaction between the TpsA and TpsB proteins in the Haemophilus influenzae HMW1 two-partner secretion system. Journal of Bacteriology. 197: 1769-1780, 2015.

Rempe KA, Spruce LA, Porsch EA, Seeholzer SH, Nørskov-Lauritsen N, St. Geme JWIII. : Unconventional N-linked glycosylation promotes trimeric autotransporter function in Kingella kingae and Aggregatibacter aphrophilus. mBio 6 (4): 1206-1215, 2015.

Kehl-Fie TE, Miller SE, St. Geme JWIII: Kingella kingae expresses type IV pili that mediate adherence to respiratory epithelial and synovial cells. Journal of Bacteriology 190: 7157-7163, 2008.

Meng G, St. Geme JWIII, Waksman G: Crystal structures of Hia fragments reveal a repetitive architecture in the Haemophilus influenzae Hia trimeric autotransporter. Journal of Molecular Biology 384: 824-36 2008.

Kehl-Fie TE, Porsch EA, Miller SE, St. Geme JWIII: Expression of Kingella kingae type IV pili is regulated by sigma54, PilS, and PilR. Journal of Bacteriology 191: 4976-4986, 2009.

Meng G, Spahich N, Kenjale R, Waksman G, St. Geme JWIII: Crystal structure of the Haemophilus influenzae Hap adhesin reveals an intercellular oligomerization mechanism for bacterial aggregation. EMBO Journal 30: 3864-3874, 2011

Kawai F, Grass S, Kim Y, Choi K-J, St. Geme JWIII, Yeo H-J: Structural insights into the glycosyltransferase activity of the Actinobacillus pleuropneumoniae HMW1C-like protein. Journal of Biological Chemistry 286: 38546-38557, 2011.

Spahich NA, Hood DW, Moxon ER, St. Geme JWIII: Inactivation of Haemophilus influenzae LPS biosynthesis genes interferes with outer membrane localization of the Hap autotransporter. Journal of Bacteriology 194: 1815-1822, 2012.

Porsch EA, Kehl-Fie TE, St. Geme JWIII: Modulation of Kingella kingae adherence to human epithelial cells by type IV pili, capsule, and a novel trimeric autotransporter. mBio 3(5): 00372, 2012.

St. Geme JWIII, Yeo H-J: A prototype two-partner secretion pathway: the Haemophilus influenzae HMW1 and HMW2 adhesin systems. Trends in Microbiology 17: 355-360, 2009.

Yagupsky P, Porsch E, St. Geme JWIII: Kingella kingae: An emerging pathogen in young children. Pediatrics 127: 557-565, 2011.

Starr, KF, Porsch EA, Heiss C, Black I, Azadi I, St. Geme JWIII : Characterization of the Kingella kingae Polysaccharide Capsule and Exopolysaccharide PLoS One. 8(9), 2013 Notes: doi:10.1371/journal.pone.0075409.

Porsch EA, Johnson MD, Broadnax AD, Garrett CK, Redinbo MR, St. Geme JW 3rd.: Calcium binding properties of the Kingella kingae PilC1 and PilC2 proteins have differential effects on type IV pilus-mediated adherence and twitching motility. J Bacteriol 195(4): 886-95, Feb 2013.

Kenjale R, Meng G, Fink DL, Juehne T, Ohashi T, Erickson HP, Waksman G, St Geme JWIII: Structural determinants of autoproteolysis of the Haemophilus influenzae Hap autotransporter. Infect Immun. 77: 4704-13, Aug 2009 Notes: doi: 10.1128/IAI.00598-09.

McCann JR, Sheets AJ, Grass S, St. Geme JWIII: The Haemophilus cryptic genospecies Cha adhesin has at least two variants that differ in host cell binding, bacterial aggregation, and biofilm formation properties. Journal of Bacteriology 196(9): 1780-8, 2014.

Spahich NA, Kenjale R, McCann JR, Ohashi T, Erickson H, St. Geme JWIII: Structural determinants of the interaction between the Haemophilus influenzae Hap autotransporter and fibronectin. Microbiology 160(Pt 6): 1182-90, Jun 2014 Notes: doi: 10.1099/mic.0.077784-0.[Epub ahead of print]

Lei J, Cai X, Ma X, Zhang L, Li Y, Dong X, St. Geme JWIII, Meng G: Recombinant expression, purification, crystallization and preliminary X-ray diffraction analysis of Haemophilus influenzae BamD and BamCD complex. Acta Crystallography F71: 234-238, 2015.

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Last updated: 04/02/2020
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