Increase in invasive Haemophilus influenzae serotype A infections during the COVID-19 pandemic in New South Wales, Australia

Winkie Fong; Elena Martinez; Verlaine Timms; Andrew Ginn; Trang Nguyen; Hossinur Rahman; Vitali Sintchenko

doi:10.1016/j.pathol.2024.02.013

Increase in invasive Haemophilus influenzae serotype A infections during the COVID-19 pandemic in New South Wales, Australia

Pathology. 2024 May 6:S0031-3025(24)00122-3. doi: 10.1016/j.pathol.2024.02.013. Online ahead of print.

Authors

Winkie Fong¹, Elena Martinez², Verlaine Timms³, Andrew Ginn⁴, Trang Nguyen², Hossinur Rahman², Vitali Sintchenko⁵

Affiliations

¹ Centre for Infectious Diseases and Microbiology - Public Health, Westmead Hospital, Westmead, NSW, Australia; Sydney Institute of Infectious Diseases, The University of Sydney, Camperdown, NSW, Australia. Electronic address: winkie.fong@health.nsw.gov.au.
² Centre for Infectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and Medical Research, New South Wales Health Pathology, Sydney, NSW, Australia.
³ Sydney Institute of Infectious Diseases, The University of Sydney, Camperdown, NSW, Australia; School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW, Australia.
⁴ Centre for Infectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and Medical Research, New South Wales Health Pathology, Sydney, NSW, Australia; Douglass Hanly Moir Pathology, Macquarie Park, NSW, Australia.
⁵ Centre for Infectious Diseases and Microbiology - Public Health, Westmead Hospital, Westmead, NSW, Australia; Sydney Institute of Infectious Diseases, The University of Sydney, Camperdown, NSW, Australia; Centre for Infectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and Medical Research, New South Wales Health Pathology, Sydney, NSW, Australia.

PMID: 38777739
DOI: 10.1016/j.pathol.2024.02.013

Abstract

Haemophilus influenzae, a causative agent of severe invasive infections such as meningitis, sepsis and pneumonia, is classified into encapsulated or typeable (represented by serotypes A to F) and non-typeable varieties (NTHi) by the presence or absence of the polysaccharide capsule. Invasive disease caused by H. influenzae type B (HIB) can be prevented through vaccination which remains the main disease control intervention in many countries. This study examined the genomic diversity of circulating H. influenzae strains associated with invasive disease in New South Wales, Australia, before and during the COVID-19 pandemic. Ninety-six isolates representing 95 cases of invasive H. influenzae infections (iHi) diagnosed between January 2017 and September 2022 were typed and characterised using whole genome sequencing. These cases were caused by serotypes A (n=24), B (n=35), E (n=3), F (n=2) and NTHi (n=32). There was an apparent decline in the number of iHi infections during the COVID-19 pandemic, with a corresponding increase in the proportion of iHi cases caused by serotype A (HIA), which returned to pre-pandemic levels in 2022. Fifteen isolates associated with HIB or non-typeable iHi were resistant to β-lactams due to a PBP3 mutation or carriage of bla_TEM-1. Further, capsular gene duplication was observed in HIB isolates but was not found in HIA. These findings provide important baseline genomic data for ongoing iHi surveillance and control.

Keywords: COVID-19 pandemic; Haemophilus influenzae; genome sequencing; invasive disease; molecular epidemiology.