Cell wall-associated protein A as a tool for immunolocalization of Staphylococcus aureus in infected human airway epithelium

Staphylococcus aureus is a common human pathogen involved in non-bronchial diseases and in genetic and acquired bronchial diseases. In this study, we applied an immunolabeling approach for in vivo and in vitro detection of S. aureus, based on the affinity of staphylococcal protein A (SpA) for the Fc region of immunoglobulins, especially IgG. Most strains of S. aureus, incl uding clinical strains, can be detected with this labeling technique. The a pproach can be used for detection and localization with transmission electr on microscopy or light-fluorescence microscopy of S. aureus in infected tis sues such as human bronchial tissue from cystic fibrosis (CF) patients. The methodology can also be applied to cell culture models with the aim of cha racterizing bacterial adherence to epithelial cells in backscattered electr on imaging with scanning electron microscopy. Application to the study of S . aureus adherence to airway epithelium showed that the bacteria did not ad here in vivo to intact airway epithelium. In contrast, bacteria adhered to the basolateral plasma membrane of columnar cells, to basal cells, to the b asement membrane and were identified beneath the lamina propria when the ep ithelium was injured and remodeled, or in vitro when the epithelial cells w ere dedifferentiated.