Abstract
The von Willebrand factor binding protein in Staphylococcus lugdunensis (vWbl) comprises four major regions: the signal peptide (S), the non-repetitive (A) region, the repeat (R) region, and the wall-associated (W) region. Previous studies have demonstrated that the R region contains 10 copies of repeating sequences; however, we reveal that the copy number of repeats in the vWbl gene varies among different S. lugdunensis isolates. In this study, an epidemiological surveillance was conducted to determine whether the copy number of repeats in vWbl in different isolates of S. lugdunensis correlates with their infectivity. The number of repeats was estimated in a total of 212 isolates, consisting of 162 isolates of oxacillin-sensitive S. lugdunensis (OSSL) and 50 isolates of oxacillin-resistant S. lugdunensis (ORSL). Our data showed that 72.5% (116/162) of OSSL isolates contained 9 (25, 15.4%), 12 (43, 26.5%), or 13 (48, 29.6%) repeats, and 90% (45/50) of ORSL isolates had 9 (32, 64%) or 13 (13, 26%) repeats. In addition, 89.6% (26 of 29) of the sequence type (ST)27 strain had 12 repeats, and 86.8% (13 of 15) of the ST4 strain had 14 repeats. Twenty-seven of the 28 isolates with nine repeats were of the staphylococcal cassette chromosome mec (SCCmec) V or Vt type and belonged to ST3, and all isolates with 13 repeats were of SCCmec II type and belonged to ST6. All isolates with nine repeats had a stop codon at the 18th codon of the third repeat, suggesting that these isolates coded for nonfunctional vWbl. Further, western blot analysis confirmed that all strains translated vWbl, and only vWbl proteins coded by genes with nine repeats were exported outside the cell. These results suggest that number of vWbl repeats in S. lugdunensis have clonal specificities and may correlate with potential pathogenicity.
Highlights
Staphylococcus lugdunensis is a member of the coagulasenegative staphylococcal species (CoNS) and has been reported to cause a wide variety of diseases, such as skin and soft tissue infections, bone and joint infections, bacteremia, and infective endocarditis (Wu et al, 2011; Yeh et al, 2015; Douiri et al, 2016; Yeh et al, 2016)
The number of sequence repeats in the R region of vWbl was determined based on the size of the sequenced PCR products, which ranged from 1739 bp (8 repeats) to 3146 bp (15 repeats) among the various isolates (Figure 1)
Most of the repeat copy numbers and their neighboring repeat copy numbers belonged to the same sequence type (ST) or neighboring STs, that is they belonged to the two founder STs, ST6 and ST29, and the STs connected to them
Summary
Staphylococcus lugdunensis is a member of the coagulasenegative staphylococcal species (CoNS) and has been reported to cause a wide variety of diseases, such as skin and soft tissue infections, bone and joint infections, bacteremia, and infective endocarditis (Wu et al, 2011; Yeh et al, 2015; Douiri et al, 2016; Yeh et al, 2016). Previous studies have identified that the von Willebrand factor binding protein (vWbp), which is secreted by S. aureus, mediates the binding of S. aureus to platelets to form an aggregated complex (Bjerketorp et al, 2002). The vWbl share partially similarities with vWbp in S. lugdunensis (Nilsson et al, 2004), which was identified by an affinity selection study of a phage display library against the von Willebrand factor (vWf) in S. lugdunensis. An initial study investigating the vWbl gene in S. lugdunensis reported 10 sequence repeats in the R region (Nilsson et al, 2004). We conducted an epidemiological study to determine whether the number of repeats in the R region of isolates of S. lugdunensis correlates with their clonality
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