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. 2022 Nov 17:13:1030242.
doi: 10.3389/fmicb.2022.1030242. eCollection 2022.

Evaluation of molecular typing for national surveillance of invasive clinical Haemophilus influenzae isolates from Denmark

Hans-Christian Slotved  1 , Thor Bech Johannesen  1 , Marc Stegger  1 , Kurt Fuursted  1
Affiliations

Evaluation of molecular typing for national surveillance of invasive clinical Haemophilus influenzae isolates from Denmark

Hans-Christian Slotved et al. Front Microbiol. .

Abstract

Haemophilus influenzae is a gram-negative coccobacillus known to cause respiratory and invasive infections. It can possess a polysaccharide capsule that can be categorized into six different serotypes (i.e., Hia, Hib, Hic, Hid, Hie, and Hif) and non-encapsulated strains that are defined as non-typeable. Furthermore, H. influenzae can be characterized into eight biotypes (I-VIII). Traditionally, isolates have been serotyped and biotyped using phenotypic methods; however, these methods are not always reliable. In this study, we evaluate the use of whole-genome sequencing (WGS) for national surveillance and characterization of clinical Danish H. influenzae isolates. In Denmark, all clinical invasive isolates between 2014 and 2021 have been serotyped using a traditional phenotypic latex agglutination test as well as in silico serotyped using the in silico programs "hinfluenzae_capsule_characterization" and "hicap" to compare the subsequent serotypes. Moreover, isolates were also biotyped using a phenotypic enzyme test and the genomic data for the detection of the genes encoding ornithine, tryptophan, and urease. The results showed a 99-100% concordance between the two genotypic approaches and the phenotypic serotyping, respectively. The biotyping showed a 95% concordance between genotyping and phenotyping. In conclusion, our results show that in a clinical surveillance setting, in silico serotyping and WGS-based biotyping are a robust and reliable approach for typing clinical H. influenzae isolates.

Keywords: Denmark; Haemophilus influenzae; capsular genes; genotyping; serotyping.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
A total of six hundred thirty-eight Haemophilus influenzae isolates were included in the study. The majority of the isolates were from blood samples (91.8%, 586), 6.1% (39) were from cerebrospinal fluid, and information on the origin of 2% (13) of isolates was not available.
FIGURE 2
FIGURE 2
Phylogenetic tree of all isolates. For each isolate, data are presented for the serotype (genotype with color), biotype (biotype with color), and clonal complex. Isolate Hinf Rd KW20 (GenBank nb. L42023) was used as a reference strain in the SNP alignment. Scale bar indicate substitutions per side.
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