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Non-typeable Haemophilus influenzae infective endocarditis in a renal transplant recipient: compromised host or
Lauren A Bertelle-Ibrahim1, Timothy F Murphy, Charmaine Kirkham
1Infectious Disease Division, Department of Veterans Affairs Western New York Healthcare System, State University of New York at Buffalo, Buffalo, New York, USA.
Abstract:
Non-typeable Haemophilus influenzae (NTHI) rarely cause endocarditis. Of the limited reports of H influenzae endocarditis, most have been due to encapsulated organisms or have had limited bacterial characterisation. We encountered a transplant recipient with native valve NTHI endocarditis and were intrigued to find no previous descriptions of this entity. Although it was tempting to ascribe this infection to our patient's immunocompromised status, we investigated his pathogen further and found that it displayed features common to invasive NTHI strains including gene expression for two IgA proteases and serum resistance. Multilocus sequence typing grouped our NTHI strain with MLST 159, a group associated with invasive NTHI infections. Our strain shared identical outer membrane protein P2 sequences and protein patterns with MLST 159 strains. Aside from providing the first characterisation of native valve NTHI infection, our investigation reveals features of epidemiologically unrelated, clonal NTHI strains that have a predilection for invasive infections.
Insights
Non-typeable Haemophilus influenzae (NTHI) rarely causes endocarditis. This study details the first case of native valve NTHI endocarditis, revealing invasive strain characteristics.
Area of Science:
- Infectious Diseases
- Microbiology
- Cardiology
Background:
- Endocarditis is uncommon with Non-typeable Haemophilus influenzae (NTHI).
- Previous cases often involved encapsulated strains or lacked detailed characterization.
- NTHI infections are typically associated with respiratory tract infections.
Observation:
- A unique case of native valve endocarditis caused by NTHI in a transplant recipient was identified.
- The NTHI strain exhibited genetic and protein expression features associated with invasive NTHI.
- These features included IgA protease production and serum resistance.
Findings:
- Multilocus sequence typing (MLST) placed the NTHI strain within the invasive MLST 159 group.
- The strain shared identical outer membrane protein P2 sequences and patterns with other MLST 159 strains.
- This represents the first characterization of native valve NTHI endocarditis.
Implications:
- The findings highlight NTHI's potential to cause invasive infections like endocarditis, even in native valves.
- Epidemiologically distinct NTHI strains may share clonal characteristics predisposing them to invasive disease.
- This case broadens the understanding of NTHI virulence factors and clinical presentations.
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