Glycomics Microarrays Reveal Differential In Situ Presentation of the Biofilm Polysaccharide Poly-N-acetylglucosamine on Acinetobacter baumannii and Staphylococcus aureus Cell Surfaces.

Andrea Flannery,Gerald B Pier,Marie Le Berre,Michelle Kilcoyne,James P O’Gara

doi:10.3390/ijms21072465

Abstract

The biofilm component poly-N-acetylglucosamine (PNAG) is an important virulence determinant in medical-device-related infections caused by ESKAPE group pathogens including Gram-positive Staphylococcus aureus and Gram-negative Acinetobacter baumannii. PNAG presentation on bacterial cell surfaces and its accessibility for host interactions are not fully understood. We employed a lectin microarray to examine PNAG surface presentation and interactions on methicillin-sensitive (MSSA) and methicillin-resistant S. aureus (MRSA) and a clinical A. baumannii isolate. Purified PNAG bound to wheatgerm agglutinin (WGA) and succinylated WGA (sWGA) lectins only. PNAG was the main accessible surface component on MSSA but was relatively inaccessible on the A. baumannii surface, where it modulated the presentation of other surface molecules. Carbohydrate microarrays demonstrated similar specificities of S. aureus and A. baumannii for their most intensely binding carbohydrates, including 3′ and 6′sialyllactose, but differences in moderately binding ligands, including blood groups A and B. An N-acetylglucosamine-binding lectin function which binds to PNAG identified on the A. baumannii cell surface may contribute to biofilm structure and PNAG surface presentation on A. baumannii. Overall, these data indicated differences in PNAG presentation and accessibility for interactions on Gram-positive and Gram-negative cell surfaces which may play an important role in biofilm-mediated pathogenesis.

Highlights

Biofilms are formed by bacteria to adapt to environmental changes and protect themselves from the host immune system and other environments
We describe the use of a lectin microarray to examine the in-situ presentation of PNAG on the cell surface of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains and a clinical isolate of A. baumannii
We suggest that succinylated WGA (sWGA) may be a better indicator for the presence of PNAG in S. aureus cultures or biofilms, but a recognition molecule that is specific for the PNAG structure itself, such as monoclonal antibody (mAb) for PNAG, may be the best identification molecule across bacterial species

Summary

Introduction

Biofilms are formed by bacteria to adapt to environmental changes and protect themselves from the host immune system and other environments. Gram-positive Staphylococcus aureus and Gram-negative Acinetobacter baumannii are leading causes of hospital-acquired biofilm infections and members of the antibiotic-resistant ‘ESKAPE’ group of pathogens [4]. Both S. aureus and A. baumannii produce poly-N-acetylglucosamine (PNAG, Figure 1a) as a major component of their biofilm matrix as well as retaining PNAG on their cell surfaces. Correlations have been made between S. aureus antibiotic susceptibility and PNAG production, and between antibiotic susceptibility and biofilm formation in A. baumannii [7,8,9]. A better understanding of the presentation and accessibility of this important biofilm component on the bacterial cell surface could help to shed light on host–pathogen interactions and immune evasion

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Discussion

Conclusion