Low occurrence of ‘non-haemolytic Haemophilus haemolyticus’ misidentified as Haemophilus influenzae in cystic fibrosis respiratory specimens, and frequent recurrence of persistent H. influenzae clones despite antimicrobial treatment

Complete Deletion of the Fucose Operon in Haemophilus influenzae Is Associated with a Cluster in Multilocus Sequence Analysis-Based Phylogenetic Group II Related to Haemophilus haemolyticus: Implications for Identification and Typing

“…Consequently, strains lacking fucK cannot be assigned a sequence type by the MLST scheme. fucK-negative strains of H. influenzae appear to be rare, and prior to this study, only 17 such isolates were reported (12,28,30). Interestingly, 13 of the 17 previously reported isolates are located on the same branch in phylogenetic group II as the 13 isolates from the present study.…”

“…While up to 20% of presumptive H. influenzae nasopharyngeal isolates can be identified as H. haemolyticus by molecular characterization (7)(8)(9), H. haemolyticus is rarely cultured from middle ear fluid (10,11), supporting the view that H. haemolyticus, in contrast to NTHi, is a respiratory commensal infrequently associated with otitis media. Reinvestigation of presumptive H. influenzae isolates, cultured from lower respiratory tract samples from cystic fibrosis patients (12) or from unselected clinical samples submitted to the laboratory on suspicion of lower respiratory tract infection (13), detected that Ͻ1% were misidentified strains, further supporting a minor pathogenic role for H. haemolyticus.…”

Difficult identification ofHaemophilus influenzae, a typical cause of upper respiratory tract infections, in the microbiological diagnostic routine

“…In sputum of COPD patients, up to 39.5% H. haemolyticus isolates were observed, at least if no association with acute exacerbations was guaranteed [5,45]. Frequency of H. haemolyticus isolates in respiratory samples of cystic fi brosis patients ranged from 0.5% [4] to 10% [38] in recent studies.…”

“…In oropharyngeal swabs of Australian indigenous children with bronchiectasis, even more H. haemolyticus strains than H. infl uenzae strains were observed [46]. A very low detection rate of only 0.5% H. haemolyticus in cystic fi brosis patients was described for Denmark [4]. For mixed upper respiratory patient samples from Germany, a frequency of H. haemolyticus isolations between 1.2% and 16.2% was calculated [14].…”

“…As shown for patients with cystic fi brosis, some persistent H. infl uenzae clones show frequent recurrence despite antimicrobial therapy [4]. Accordingly, chronic infl ammation may consequently result.…”