Screening for staphylococcal superantigen genes shows no correlation with the presence or the severity of chronic rhinosinusitis and nasal polyposis

Abstract

Background: Staphylococcus aureus secretes numerous exotoxins which may exhibit superantigenic properties. Whereas the virulence of several of them is well documented, their exact biological effects are not fully understood. Exotoxins may influence the immune and inflammatory state of various organs, including the sinonasal mucosa: their possible involvement in chronic rhinosinusitis has been suggested and is one of the main trends in current research. The aim of this study was to investigate whether the presence of any of the 22 currently known staphylococcal exotoxin genes could be correlated with chronic rhinosinusitis.

Methodology/principal findings: We conducted a prospective, multi-centred European study, analysing 93 Staphylococcus aureus positive swabs taken from the middle meatus of patients suffering from chronic rhinosinusitis, with or without nasal polyposis, and controls. Strains were systematically tested for the presence of the 22 currently known exotoxin genes and genotyped according to their agr groups. No direct correlation was observed between chronic rhinosinusitis, with or without nasal polyposis, and either agr groups or the presence of the most studied exotoxins genes (egc, sea, seb, pvl, exfoliatins or tsst-1). However, genes for enterotoxins P and Q were frequently observed in nasal polyposis for the first time, but absent in the control group. The number of exotoxin genes detected was not statistically different among the 3 patient groups.

Conclusions/significance: Unlike many previous studies have been suggesting, we did not find any evident correlation between staphylococcal exotoxin genes and the presence or severity of chronic rhinosinusitis with or without nasal polyposis.

Figure 1. Genotyping tree.

MLVA genotyping of isolates recovered from patients suffering chronic rhinosinusitis from five different geographic locations (B. Brugg; Z. Zagreb; P. Paris; L. London; G. Geneva). Control isolates (CTL) from Geneva patients are also depicted (a single isolate per patient is shown). Categories are indicated between brackets. Scale displays the relations between isolates. Isolates with a maximal distance 0.1 are considered as clonal. CRSsNP = Chronic Rhinosinusitis without Nasal Polyposis group; NP1-2-3 = Nasal Polyposis grade 1-2-3 groups; Ctl = control group.

Figure 2. Rates of patients carrying S. aureus.

Percentage, per group of patients, of S. aureus with (se +) or without (se −) exotoxin gene.

Figure 3. Identified exotoxins.

Number of different staphylococcal exotoxins identified in the CRSwNP, CRSsNP and control groups, in percentage per groups' population, in order to compare the three groups equally.