Individual strains of group A streptococci (GAS) differ in virulence, but the reasons for these differences are incompletely understood. To determine if the ability of GAS to cause invasive disease corresponded with their capacity to adhere to or invade epithelial cells, 63 clinical isolates of GAS (40 from patients with systemic infection and 23 from superficial disease) were examined in quantitative assays of bacterial adhesion to and invasion of HEp-2 cells, a continuous line of human pharyngeal epithelial cells. The results showed that individual isolates of GAS varied considerably in their ability to adhere to and penetrate HEp-2 cells. However, on the whole, strains from patients with invasive disease adhered to cells in numbers 1.5 greater than those from superficial infection. Paradoxically, strains from patients with invasive disease invaded HEp-2 cells to a significantly lesser extent than those from superficial sites, with a two-fold difference in invasion index (defined as the percentage of cell-associated bacteria located intracellularly). To determine if these differences were caused by differences in the production of hyaluronic acid capsule or M protein by the two groups of bacteria, the adherence and invasive capacities of bacteria carrying defined mutations in the genes for these factors were examined. Although M18-protein-deficient bacteria were less adherent to HEp-2 cells than the wild-type, neither the hyaluronic acid capsule nor the M protein had a significant influence on the ability of GAS to adhere to or invade HEp-2 cells. The results of this study demonstrate that there are biological differences between GAS isolates associated with invasive and superficial diseases and that these differences can be demonstrated by an assay of bacterial adherence to and invasion of HEp-2 epithelial cells.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error