Identification and characterization of “Haemophilus quentini” strains causing invasive disease in Ontario, Canada (2016-2018).

Haemophilus influenzae is a well-established human pathogen capable of causing a range of respiratory and invasive diseases. Since the 1970s it has been observed that a non-typeable cryptic genospecies of H. influenzae, most often biotype IV has been associated with the genitourinary tract of females and invasive neonatal infections. This distinct genospecies has been provisionally named “Haemophilus quentini”. Here we report seven invasive cases of “H. quentini” disease in patients from Ontario, Canada over a 2 year period. Significantly, to date while most reports of invasive disease with “H. quentini” have been in neonates, we observed 5 cases in adults (3 women of childbearing age, and 2 seniors) as well as 2 in neonates. Identification of “H. quentini” is challenging and was not possible by frontline laboratories requiring work at the reference laboratory level. We describe in detail the biochemical, MALDI-Tof MS, PCR results for several targets including16S rRNA gene and multi-locus sequence typing (MLST) of the seven Ontario “H. quentini” isolates and several controls. Our data combined with that of other publications supports the fact that “H. quentini” is distinct from H. influenzae and Haemophilus haemolyticus. This organism is recognized as a pathogen of neonates but we hypothesize that it may be under-recognized as an important pathogen in adults as well, particularly pregnant women. By sharing the detailed descriptions of these isolates, we hope to enable other laboratories to better identify “H. quentini” so that the true prevalence of this organism and disease can be explored.