Abstract
Haemophilus influenzae and Streptococcus pyogenes colonize overlapping regions of the nasopharynx and oropharynx. The effect of 10 H. influenzae strains (5 non-piliated parent strains and 5 piliated daughter strains) on adherence of S. pyogenes to human respiratory epithelial cells was assessed in this study. A 39.6% and 49.0% increase in the number of adherent S. pyogenes was observed in Chang epithelial cells if the cells were already colonized with 2 out of 5 non-piliated strains of H. influenzae (p <0.05). Four out of 5 piliated strains of H. influenzae enhanced the adherence of S. pyogenes to Chang cells by 103.5%, 113.6%, 109.7% (p<0.01) and 53.4% (p<0.05). With A549 epithelial cells, non-piliated strains of H. influenzae did not affect the adherence of S. pyogenes (p>0.05), but a 36.9% (p<0.05), 62.9% (p<0.01) and 32.1% (p<0.05) increase in the number of adherent S. pyogenes was found with 3 out of 5 piliated strains of H. influenzae. These results indicate that increases of S. pyogenes adherence to epithelial cells may be modulated species-specifically by H. influenzae, especially by piliated H. influenzae.