Haemophilus influenzae and Haemophilus haemolyticus in tonsillar cultures of adults with acute pharyngotonsillitis

Objective: The aim of this study was to evaluate the clinical implication of Haemophilus haemolyticus, one of the closest relative of Haemophilus influenzae, on acute pharyngotonsillitis. Methods: We applied polymerase chain reaction (PCR) for 16S ribosomal DNA (rDNA) and IgA protease gene (iga) to distinguish H. haemolyticus and H. influenzae. Results: Among the 199 Haemophilus spp. isolated from 214 patients with acute pharyngotonsillitis, 52 (24.3%) H. influenzae strains and 23 (10.7%) H. haemolyticus strains were identified by polymerase chain reaction (PCR) for 16S rDNA and IgA protease gene (iga). All H. haemolyticus strains showed hemolysis on horse blood agar and there were no other Haemophilus spp., nonhemolytic H. haemolyticus and H. influenzae variant strains that had absent iga gene. H. hemolyticus showed close genetic relationship with H. influenzae evaluated by pulsed field gel electrophoresis (PFGE). The cases of acute pharyngotonsillitis showing WBC=7000/mm³ or CRP=8mg/dl were frequently found among cases with H. influenzae rather than cases with H. haemolyticus. Conclusion: H. haemolyticus is a pharyngeal commensal that is isolated frequently from adults with acute pharyngotonsillitis.