TABLE 2.

Quantitative assessment of interactions between serotype M49 GAS wild-type or lsp operon mutant bacteria and immobilized matrix proteins or A549 eukaryotic cells

Parametera	Mean ± SEM
	Wild type	lsp mutant	ORF2 mutant
% Binding to:
Fibronectin	100 ± 18	50 ± 38	105 ± 30
Laminin	100 ± 29	59 ± 13*	64 ± 22*
Collagen I	100 ± 22	95 ± 27	103 ± 21
% Eukaryotic cell attachment	11.3 ± 5.7	5.8 ± 2.8*	3.0 ± 1.2*
% Eukaryotic cell internalization	5.5 ± 3.7	2.5 ± 0.9*	1.4 ± 1.3*

^aBinding to immobilized human matrix proteins during a 1-h incubation period was measured by utilizing FITC-labeled whole bacteria cultured to the stationary phase. Values obtained with wild-type bacteria were arbitrarily defined as 100%. Values of lsp and ORF2 mutants were calculated in relation to the corresponding wild-type values. Eukaryotic cell attachment and internalization were assessed by using stationary-phase bacteria and A549 epithelial cells according to a protocol for a classical antibiotic protection assay. The initial inoculum and the ratio of adherent to internalized bacteria were quantitated by viable counts. The initial inoculum was arbitrarily defined as 100%, and adherent/internalized bacteria were calculated in relation to the corresponding initial inoculum. Each assay was repeated on at least four independent occasions. Variation between assays is shown as a standard deviation of the mean. Values marked with asterisks indicate statistically significant differences (P < 0.05) according to the Mann-Whitney U test.