[Correlation study of Staphylococcus aureus superantigens and formation of human ear keloid]

Objective: To investigate the correlation of Staphylococcus aureus superantigens and human ear keloid formation. Methods: The retrospective case-control study method was used. The discarded keloid tissue was collected from 10 patients (9 females and 1 male, aged 19-59 years) with ear keloid after core excision of ear keloid, and the discarded normal skin tissue was collected from 3 female patients (aged 20-24 years) with pigmented nevus after operation, who were admitted to affiliated Hospital of Nantong University from June 2017 to March 2018. The exudation from ear keloid surface was collected for bacteria culture and identification. The keloid and normal skin tissue were collected to detect the protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+toxic shock syndrome toxin-1 (TSST-1) by Western blotting, and the keloid was divided into superantigen positive group and superantigen negative group according to the protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+TSST-1. The protein expressions of T cell receptor (TCR) V β of keloid in 2 groups were detected by Western blotting. Collagen fibers formation and inflammatory cells infiltration in keloid dermis of 2 groups were observed by Masson and hematoxylin eosin staining, respectively. Enzyme-linked immunosorbent assay method was used to detect expression of Staphylococcus aureus enterotoxin A, enterotoxin B, and TSST-1 in keloids with superantigen positive. Data were statistically analyzed with paired sample t test. Results: Bacteria were cultured from the exudation on ear keloid surface, hemolysis was observed around the dominant bacteria after being cultured for 24 hours, and the colony was white or golden yellow, which was identified as Staphylococcus aureus. The protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+TSST-1 of normal skin was negative in 3 patients, and the protein expression was 0.267±0.016. The protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+TSST-1 of keloid was positive in 4 patients, with the protein expression of 0.472±0.016, which was included into superantigen positive group, and the protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+TSST-1 of keloid was negative in 6 patients, with the protein expression of 0.255±0.004, which was included into superantigen negative group. The protein expression of Staphylococcus aureus enterotoxin A+enterotoxin B+TSST-1 of keloid in superantigen positive group was obviously higher than that of keloid in superantigen negative group and that in normal skin (t=15.22, 8.63, P＜0.01). The protein expression of TCR Vβ in keloid of superantigen positive group was 0.389±0.023, which was significantly higher than 0.169±0.014 in superantigen negative group (t=8.62, P＜0.01). Masson staining showed that a large number of collagen fibers existed in dermis of keloid in 2 groups. HE staining showed that there were a small number of inflammatory cells infiltration around the blood vessels of keloid dermis in superantigen negative group and a large number of inflammatory cells infiltration around the blood vessels of keloid in superantigen positive group. Among the 4 patients with superantigen positive keloid, Staphylococcus aureus enterotoxin A was positive in 2 patients, Staphylococcus aureus enterotoxin B was positive in 2 patients, and among that Staphylococcus aureus enterotoxin A and enterotoxin B were both positive in 1 patient, with no TSST-1 detected in any patient. Conclusions: The superantigen secreted by Staphylococcus aureus is one of the many causes of ear keloid, which may be related to the activation of keloid signal pathway by superantigen of Staphylococcus aureus.