Staphylococcus aureus Induces Eosinophil Cell Death Mediated by α-hemolysin

Staphylococcus aureus, a major human pathogen, exacerbates allergic disorders, including atopic dermatitis, nasal polyps and asthma, which are characterized by tissue eosinophilia. Eosinophils, via their destructive granule contents, can cause significant tissue damage, resulting in inflammation and further recruitment of inflammatory cells. We hypothesised that the relationship between S. aureus and eosinophils may contribute to disease pathology. We found that supernatants from S. aureus (SH1000 strain) cultures cause rapid and profound eosinophil necrosis, resulting in dramatic cell loss within 2 hours. This is in marked contrast to neutrophil granulocytes where no significant cell death was observed (at equivalent dilutions). Supernatants prepared from a strain deficient in the accessory gene regulator (agr) that produces reduced levels of many important virulence factors, including the abundantly produced α-hemolysin (Hla), failed to induce eosinophil death. The role of Hla in mediating eosinophil death was investigated using both an Hla deficient SH1000-modified strain, which did not induce eosinophil death, and purified Hla, which induced concentration-dependent eosinophil death via both apoptosis and necrosis. We conclude that S. aureus Hla induces aberrant eosinophil cell death in vitro and that this may increase tissue injury in allergic disease

Serum eosinophil cationic protein in children with atopic dermatitis

BACKGROUND: Eosinophil cationic protein (ECP) is a cytotoxic agent secreted by activated eosinophils during allergic and inflammatory processes. The aim of the study was to determine the ECP level, absolute and relative eosinophil count and IgE antibodies in children with atopic dermatitis (AD) compared with those of nonatopic children, and to assess the correlation of these laboratory parameters with the clinical severity of AD. ----- METHODS: This prospective study comprised 70 children. There were 49 children with AD aged 3-36 months, and the control group comprised 21 children with a negative personal and family history for atopic diseases. Detailed history, serum ECP levels (UniCAP FEIA), relative and absolute eosinophil counts and total serum IgE antibodies were determined in both groups. In the children with AD, skin involvement was measured by the SCORAD index. ----- RESULTS: The calculated SCORAD index was between 16 and 83. IgE antibodies, relative and absolute eosinophil counts showed a significantly wider range of values and a statistically higher median (P 0.05). The same was found for the correlation of serum ECP and intensity of skin changes (r = -0.095) and serum ECP and subjective symptoms (r = -0.045). The correlation was positive, but weak and statistically not significant for the serum ECP and extent of the skin lesions (r = 0.079, P > 0.05). ----- CONCLUSION: Elevated levels of ECP, relative and absolute eosinophil counts, as well as IgE antibodies were determined in the patients with AD. As these laboratory findings did not correlate with the severity of AD, they can be considered only as additional methods in the evaluation of patients with AD