The ability of Group A streptococcus to adhere to immortalized human skin versus throat cell lines does not reflect their predicted tissue tropism.

OBJECTIVES: To determine if emm pattern-inferred tissue tropisms of Group A streptococcus strains is reflected in their ability to adhere to immortalized human HaCat (keratinocyte) and Detroit 562 (pharyngeal) cell lines.

METHODS: Human epithelial cell line monolayers were inoculated with Group A streptococcus, and the percentage of adhered bacteria after a 1-h incubation period was calculated.

RESULTS: Of the 21/69 inferred-skin-tropic, and the 25/69 inferred-throat-tropic isolates no preferential adherence was observed to a particular cell line. The 23/69 strains classified as 'generalists', however, showed an overall greater ability to adhere to both cell lines.

CONCLUSIONS: Predicted tissue-tropism based on emm patterns is not reflected by preferential adherence to a specific cell line, suggesting that early adhesion events may not be as important in establishing infection at a particular ecological niche than originally expected.