Emergence of a clone of invasive fucK-negative serotype e Haemophilus influenzae in British Columbia.

Background: Introduction of the Haemophilus influenzae serotype b (Hib) conjugate vaccine has changed the epidemiology of invasive H. influenzae disease, with most infections now caused by non-typeable (non-encapsulated) and non-Hib encapsulated strains. Methods: We describe nine invasive serotype e H. influenzae (Hie) from British Columbia that were determined to have complete deletion of their fucose operon genes. These nine isolates were recovered from blood cultures of three female and six male patients during 2011-2018, with eight recovered in the past 4 years. Results: All nine isolates were biotype IV, with eight showing identical pulsed field gel electrophoresis (PFGE) profiles, whereas the ninth showed 95% similarity. PFGE analysis also showed these fucose operon-negative Hie to be most (94%) similar to the multi-locus sequence type (ST)-18, the most common ST among Hie in British Columbia. These nine fucose operon-negative Hie represented 27.3% of the 33 invasive Hie isolated in British Columbia from 2010 to 2018. Conclusion: Deletion of the fucose operon did not appear to impact the transmission ability of these strains or their ability to cause invasive disease.

Historique:  L'adoption du vaccin conjugué contre l'Haemophilus influenzae de sérotype b (Hib) a modifié l'épidémiologie de la maladie à H. influenzae invasive, car la plupart des infections sont désormais causées par des souches non typables (non encapsulées) plutôt que par des souches encapsulées non Hib. Méthodologie: Les auteurs décrivent neuf cas d'H. influenzae de sérotype e (Hie) invasif de la Colombie-Britannique, dont la délétion des gènes de l'opéron fucose était considérée comme complète. Ces neuf isolats ont été prélevés dans les hémocultures de trois patientes et de six patients entre 2011 et 2018, dont huit récupérés dans les quatre années précédentes. Résultats: Les neuf isolats étaient de biotype IV, et huit possédaient un profil d'électrophorèse sur gel à champ pulsé (PFGE) identique, alors que le neuvième était similaire à 95 %. L'analyse PFGE a également révélé que les Hie négatifs à cet opéron fucose sont les plus (94 %) semblables au typage génomique multilocus (ST)-18, qui sont les ST les plus fréquents dans les souches de Hie en Colombie-Britannique. Ces neuf Hie négatifs à l'opéron fucose représentaient 27,3 % des 33 Hie invasifs isolés en Colombie-Britannique entre 2010 et 2018. Conclusion: La délétion de l'opéron fucose ne semblait pas avoir d'effet sur la capacité de transmission de ces souches ni sur la capacité de provoquer d'autres maladies invasives.

Nonencapsulated or nontypeable Haemophilus influenzae are more likely than their encapsulated or serotypeable counterparts to have mutations in their fucose operon.

Population biology of Haemophilus influenzae can be studied by multilocus sequence typing (MLST), and isolates are assigned sequence types (STs) based on nucleotide sequence variations in seven housekeeping genes, including fucK. However, the ST cannot be assigned if one of the housekeeping genes is absent or cannot be detected by the current protocol. Occasionally, strains of H. influenzae have been reported to lack the fucK gene. In this study, we examined the prevalence of this mutation among our collection of H. influenzae isolates. Of the 704 isolates studied, including 282 encapsulated and 422 nonencapsulated isolates, nine were not typeable by MLST owing to failure to detect the fucK gene. All nine fucK-negative isolates were nonencapsulated and belonged to various biotypes. DNA sequencing of the fucose operon region confirmed complete deletion of genes in the operon in seven of the nine isolates, while in the remaining two isolates, some of the genes were found intact or in parts. The significance of these findings is discussed.

Canadian beta-lactamase-negative Haemophilus influenzae isolates showing decreased susceptibility toward ampicillin have significant penicillin binding protein 3 mutations.

Nineteen beta-lactamase-negative ampicillin-resistant (BLNAR) and 2 beta-lactamase-positive amoxicillin-clavulanic acid-resistant Canadian Haemophilus influenzae strains were characterized. All 21 isolates were found to have the N526K mutations in their ftsI genes, and their ampicillin MIC(50) values were 4-8 times that of beta-lactamase-negative ampicillin-susceptible strains. The difficulty in detection of BLNAR strains was discussed.