Oral Presentation Australian Microbial Ecology 2022

Assessing the Role of Pharyngeal Cell Surface Glycans in Group A Streptococcus Biofilm Formation (#47)

Heema Vyas 1 2 3 , Anuk Indraratna 2 3 , Arun Everest-Dass 4 , Nicolle Packer 4 5 , David De Oliveira 6 , Marie Ranson 2 3 , Jason McArthur 2 3 , Martina Sanderson-Smith 2 3
  1. The University of Sydney, Redfern, NSW, Australia
  2. llawarra Health and Medical Research Institute, Wollongong, NSW, Australia
  3. School of Chemistry and Molecular Bioscience, Molecular Horizons, The University of Wollongong, Wollongong, NSW, Australia
  4. Institute for Glycomics, Griffith University, Southport , Queensland, Australia
  5. Department of Molecular Sciences, Macquarie University, Sydney, NSW, Australia
  6. School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia

Streptococcus pyogenes (Group A Streptococcus; Group A streptococci; GAS) causes 700 million infections and accounts for half a million deaths per year. Antibiotic treatment failure rates of 20–40% have been observed. The role host cell glycans play in GAS biofilm formation in the context of GAS pharyngitis and subsequent antibiotic treatment failure has not been previously investigated. GAS serotype M12 GAS biofilms were assessed for biofilm formation on Detroit 562 pharyngeal cell monolayers following enzymatic removal of all N-linked glycans from pharyngeal cells with PNGase F. Removal of N-linked glycans resulted in an increase in biofilm biomass compared to untreated controls. Further investigation into the removal of terminal mannose and sialic acid residues with α1-6 mannosidase and the broad specificity sialidase (Sialidase A) also found that biofilm biomass increased significantly when compared to untreated controls. Increases in biofilm biomass were associated with increased production of extracellular polymeric substances. Furthermore, it was found that M12 GAS biofilms grown on untreated pharyngeal monolayers exhibited a 2500-fold increase in penicillin tolerance compared to planktonic GAS. Pre-treatment of monolayers with exoglycosidases resulted in a further doubling of penicillin tolerance in resultant biofilms. Lastly, an additional eight GAS emm-types were assessed for biofilm formation in response to terminal mannose and sialic acid residue removal. As seen for M12, biofilm biomass on monolayers increased following the removal of terminal mannose and sialic acid residues, however, significant increases in biofilm biomass were both strain and terminal glycan residue dependent. Collectively, these data demonstrate the effect of host glycosylation on GAS biofilm formation, and GAS biofilm formation as an important proponent in penicillin tolerance.