Varghese, Alyssa; Crandall, Hillary; Blaschke, Anne (University of Utah)
Faculty Advisor: Crandall, Hillary (University of Utah, Department of Pediatrics); Blaschke, Anne (University of Utah, Department of pediatrics)
Haemophilus influenzae serotype b (Hib) causes serious bacterial infections in children associated with high morbidity and mortality. The incidence of Hib disease decreased with widespread vaccination in the mid-1980's. However, other H. influenzae serotypes, such as serotype a (Hia), have emerged in specific pediatric populations, including Utah and indigenous populations in Alaska and Canada. Hia appears to cause disease similar to Hib in both severity and disease presentations.
Cases of invasive H. influenzae disease in children <18 years were identified via a search of electronic medical records within the Intermountain Healthcare system. Phylogenetic division was determined using sodC PCR. Whole genome sequencing (WGS) was performed on available isolates. Gene presence and absence data from resulting assemblies were utilized to build a relationship tree from all available Hia isolates, as well as select Hib, H. influenzae serotype f (Hif), and non-typeable H. influenzae (NTHi) isolates. Multi-locus sequence type (ST) was extracted from WGS data for each isolate.
118 cases of invasive H. influenzae disease were identified from 2007 to 2017. Fifty-one (43.2%) cases were Hia and 11 (9.3%) were Hib. Twenty-eight of 51 (56%) Hia isolates were available for further molecular analysis. Three STs were identified: ST56, ST62, and ST576. Twenty-one isolates (75%) belonged to ST62, clonal division II. The relationship tree indicates that ST62 Hia isolates are most closely related to each other and more closely related to Hif than to other Hia and Hib.
The molecular epidemiology of invasive Hia disease in Utah is unique, with a predominance of ST62 strains, a ST that has been infrequently reported in other studies of invasive Hia. Further genomic analysis will help us understand genetic determinants of virulence. These analyses will be critical in characterizing the clinical and molecular features of invasive H. influenzae disease in Utah.