Production of staphylococcal impetigo-like lesion on human skin explants in culture

Abstract

We produced a highly reproducible experimental impetigo-like lesion in normal human skin explants in culture. The three Staphylococcus aureus strains we used were an isolate from a human impetigo (E strain), an isolate from a human furunculosis (N strain) and ATCC 29213 strain. E strain was a protein A positive, coagulase type V, producer of exfoliative toxin (ET) and β-toxin. N strain was a coagulase type IV, ET non-producer and α-toxin positive. ATCC 29213 was a coagulase type II, ET non-producer, and α-, β-, and δ-toxin positive. Normal human skin samples were obtained from 8 adult skin surgery patients. One specimen was obtained from human oral mucosa. Small pieces of the samples were slightly abraded on the epidermal surface and cultured on lens paper rafts floating in Eagle's Minimum Essential Medium in an atmosphere of 5% CO 2 and 95% air. Fifty microliters of the respective bacterial suspensions were applied to the epidermal surfaces of the explants. The inoculated surfaces were then occluded under sterile plastic plaster. Histologically, the formation of intraepidermal blisters at the granular layer level with acantholytic cells was observed in all 8 of the skin specimens at 10 h after inoculation with E strain. The specimen from an oral mucous membrane did not produce similar changes with any of the three S. aureus strains. Neither N or ATCC strains developed bullae in the epidermis at 6, 10 or 18 h after inoculation. Immunofluorescent examination revealed that the inner surfaces of blisters in the epidermis were lined with anti-ETA antibody. Under the electron microscope, the blisters of the specimens which had been inoculated with strain E contained only a few S. aureus cells. These results suggest that blister formation at the granular layer level with acantholytic cells is mediated by ET action at the granular layer level and occurs without invasion of lymphocytes or neutrophils, or the involvement of any serum components. Therefore, under appropriate conditions, impetigo could develop even in adults.