The persistence of intracellular Staphylococcus aureus in the sinuses: a longitudinal study.

BACKGROUND: Staphylococcus aureus (S. aureus) can reside within the sinonasal mucosa in chronic rhinosinusitis patients and causes recurrent infections. Within the host cell, S. aureus can evade host immune detection enabling its own survival. We hypothesise that S. aureus can persist within the sinonasal epithelium for a prolonged period without immune activation. METHODOLOGY: Patients with chronic rhinosinusitis with nasal polyps (CRSwNP) undergoing two sinus surgeries were included. Immunohistochemistry and Haematoxylin and Eosin stains were used to determine intracellular S. aureus (ICSA) status and inflammatory cell count, respectively. One-way ANOVA and paired t-tests were performed for comparison between ICSA subgroups and within each subgroup, respectively. RESULTS: Histopathological specimens from 34 patients (68 procedures) were included. ICSA positivity (ICSA+) was seen in 43 specimens (63.2%) from 26 (76%) patients. 18 (52.9%) of those were ICSA+ in both operations while 8 (23.5%) patients were ICSA+ in only one of the operations. 8 (23.5%) patients were ICSA negative in both operations. There was no difference in the number of eosinophils, lymphocyte and neutrophils between ICSA subgroups. CONCLUSIONS: This study demonstrated that S. aureus is found intracellularly within CRSwNP tissue at multiple time points without an increase in the number of eosinophils, lymphocytes and neutrophils. This finding supports our hypothesis that ICSA is able to escape from host detection and resides within the sinonasal mucosa despite intense treatment.

Small-colony variants and phenotype switching of intracellular Staphylococcus aureus in chronic rhinosinusitis.

BACKGROUND: Chronic rhinosinusitis (CRS) has been linked to the gram-positive bacteria Staphylococcus aureus (S. aureus) in its biofilm or intracellular forms. Recent evidence suggests that S. aureus also exists in a small-colony variant (SCV) form as a mechanism of altering its virulence capabilities. The aim of this study was to investigate the presence of SCVs in sinonasal mucosa of CRS patients and whether the phenomenon of phenotype switching can be applied to intracellular epithelial infections. METHODS: Sinonasal specimens were examined for the presence of intramucosal S. aureus and characterized to the strain level. An airway epithelial cell culture infection model was utilized to investigate whether bacteria were capable of alterations in virulence phenotype. RESULTS: Intramucosal organisms harvested from sinonasal biopsies demonstrate phenotypic growth patterns and lack of coagulase activity consistent with SCVs. Intracellular infection of airway epithelial cell cultures with S. aureus led to decreased secretion of enterotoxins and phenotypic growth alterations consistent with SCVs. CONCLUSIONS: Regulation of S. aureus virulence factors is a dynamic process, and exposure to the intracellular environment appears to provide the necessary conditions to enable these alterations in an attempt for the bacterium to survive and persist within host tissues. Further work is required to ascertain whether SCVs in CRS hold a clinically relevant pathogenic role in recalcitrant disease.

Inflammasome gene expression alterations in Staphylococcus aureus biofilm-associated chronic rhinosinusitis.

BACKGROUND: The role of inflammasomes in chronic inflammation has been the subject of intense research in recent years. Chronic rhinosinusitis (CRS), a persistent inflammatory disease, continues to be investigated hoping that a clearer pathophysiologic description will guide discovery of future treatment modalities. This study investigates the role of inflammasome complexes in CRS patients with Staphylococcus aureus biofilm infection, a key culprit associated with disease severity and recalcitrance. METHODOLOGY: Sinonasal tissue samples were collected from CRS patients with (P+) and without (P-) polyps and controls. S. aureus biofilm status was obtained using fluorescence in situ hybridization and classified as biofilm positive (B+) or negative (B-). RNA was analysed using a Human Inflammasome PCR array, profiling the expression of 84 genes involved in inflammasome function. RESULTS: Sixteen samples were obtained: 5 B+P+, 5 B-P- and 6 controls. Comparing B+P+ vs. controls showed the greatest number of differentially expressed genes. In particular, Absent in Melanoma 2 (AIM2) was consistently and significantly up-regulated in the B+P+ vs. B-P- and controls. In contrast, when comparing the B-P- vs. controls, no genes showed significant changes. CONCLUSION: Our results indicate the involvement of inflammasome complexes and their signalling pathways in CRS patients with polyps and S. aureus biofilms. In particular, AIM2, activated by intracellular double-stranded DNA, is up-regulated in this group, implying that S. aureus may play a role in intracellular triggering of the inflammasome response. Studies with further patient stratification and assessing corresponding protein expression are needed to further characterize the role of inflammasomes in CRS.

Is nasal steroid spray bottle contamination a potential issue in chronic rhinosinusitis?

BACKGROUND: Intranasal steroids are the first line of treatment for chronic rhinosinusitis. Although contamination of adjunctive devices (e.g. irrigation bottles) has been much investigated, little is known about nasal contamination of the metered-dose spray bottles used to deliver intranasal steroids, and the potential influence on disease chronicity. METHODS: Twenty-five prospectively recruited patients with stable chronic rhinosinusitis underwent microbiological analysis of their nasal vestibule and middle meatus and also of their steroid bottle tip and contents. Additionally, bottle tips were inoculated in vitro with Staphylococcus aureus and various sterilisation techniques tested. RESULTS: For 18 of the 25 (72 per cent) patients, both nasal and bottle tip swabs grew either Staphylococcus aureus or coagulase-negative staphylococci. Staphylococcus aureus was cultured from 7 of the 25 (28 per cent) patients, and 5 of these 7 had concomitant bacterial growth from both nose and steroid bottle. Thus, the cross-contamination rate was 71 per cent for Staphylococcus aureus infected patients and 20 per cent overall. Sterilisation was effective with boiling water, ethanol wipes and microwaving, but not with cold water or dishwashing liquid. CONCLUSION: Nasal steroid spray bottle tips can become contaminated with sinonasal cavity bacteria. Simple sterilisation methods can eliminate this contamination. Patient education on this matter should be emphasised.