Fbl-Typing of Staphylococcus lugdunensis: A Frontline Tool for Epidemiological Studies, but Not Predictive of Fibrinogen Binding Ability.

Sandrine Dahyot,Jérémie Lebeurre,Floriane Laumay,Gilles Prévost,Martine Pestel-Caron,Patrice François,Ludovic Lemée,Xavier Argemi,Charline Dubos

doi:10.3389/fmicb.2019.01109

Abstract

Staphylococcus lugdunensis is increasingly recognized as a potent pathogen, responsible for severe infections with an outcome resembling that of Staphylococcus aureus. Here, we developed and evaluated a tool for S. lugdunensis typing, using DNA sequence analysis of the repeat-encoding region (R-domain) in the gene encoding the fibrinogen (Fg)-binding protein Fbl (fbl-typing). We typed 240 S. lugdunensis isolates from various clinical and geographical origins. The length of the R-domain ranged from 9 to 52 repeats. fbl-typing identified 54 unique 18-bp repeat sequences and 92 distinct fbl-types. The discriminatory power of fbl-typing was higher than that of multilocus sequence typing (MLST) and equivalent to that of tandem repeat sequence typing. fbl-types could assign isolates to MLST clonal complexes with excellent predictive power. The ability to promote adherence to immobilized human Fg was evaluated for 55 isolates chosen to reflect the genetic diversity of the fbl gene. We observed no direct correlation between Fg binding ability and fbl-types. However, the lowest percentage of Fg binding was observed for isolates carrying a 5′-end frameshift mutation of the fbl gene and for those harboring fewer than 43 repeats in the R-domain. qRT-PCR assays for some isolates revealed no correlation between fbl gene expression and Fg binding capacity. In conclusion, this study shows that fbl-typing is a useful tool in S. lugdunensis epidemiology, especially because it is an easy, cost-effective, rapid and portable method (http://fbl-typing.univ-rouen.fr/). The impact of fbl polymorphism on the structure of the protein, its expression on the cell surface and in virulence remains to be determined.

Highlights

Staphylococcus lugdunensis is a member of the coagulase-negative staphylococci (CoNS)
Staphylococcus lugdunensis is increasingly recognized as a potent pathogen, responsible for severe infections with an outcome resembling that of Staphylococcus aureus
We examined the complete sequence variation of the fbl gene in published S. lugdunensis genomes, and discovered a 4 bp deletion occurring at position 12 from the start codon for two isolates (Figure 1B)

Summary

Introduction

Staphylococcus lugdunensis is a member of the coagulase-negative staphylococci (CoNS) It belongs to the normal human skin flora, colonizing several distinct niches such as perineal and inguinal areas (Bieber and Kahlmeter, 2010) but is increasingly recognized as a potent human pathogen (Frank et al, 2008). S. lugdunensis can cause various types of infections, ranging from localized to systemic diseases (Zinkernagel et al, 2008; Heldt Manica and Cohen, 2017) It has mainly been reported in skin and soft tissue infections (Papapetropoulos et al, 2013), but it is responsible for catheter-related bloodstream infections, bone and joint infections (Argemi et al, 2017) and severe infective endocarditis (Non and Santos, 2017). Some in vitro studies have suggested the existence of several virulence factors, including hemolysins, adhesion proteins [Fg-binding protein Fbl (Mitchell et al, 2004) and von Willebrand factor-binding protein vWbl (Nilsson et al, 2004b)] and iron-regulated surface determinant proteins (Heilbronner et al, 2016)

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