Invasive serotype a Haemophilus influenzae infections with a virulence genotype resembling Haemophilus influenzae type b: emerging pathogen in the vaccine era?

E. E. Adderson, C. L. Byington, L. Spencer, A. Kimball, M. Hindiyeh, K. Carroll, S. Mottice, E. K. Korgenski, J. C. Christenson, A. T. Pavia

Research output: Contribution to journalArticle

78 Scopus citations

Abstract

OBJECTIVE: Haemophilus influenzae type b causes severe disease in nonimmune infants and young children; other serotypes are uncommon pathogens and thought to have low virulence. Some have hypothesized that with the virtual elimination of H influenzae type b, other serotypes might acquire virulence traits and emerge as important pathogens of children. We describe the clinical, epidemiologic, and molecular biologic features of 5 cases of severe disease attributable to Haemophilus influenzae type a. METHODS: After observing 4 cases of invasive disease caused by H influenzae type a, we reviewed microbiology records at 3 reference laboratories that perform all serotyping in Utah and surveillance databases. Strains of H influenzae type a and control strains were examined by Southern blotting with the use of the cap probe pUO38 and by pulsed-field gel electrophoresis. The putative virulence mutation, the IS1016-bexA deletion, was detected by polymerase chain reaction amplification and sequencing. RESULTS: During a 10-month period, we observed 5 children with severe invasive disease caused by H influenzae type a. No isolates of H influenzae type a had been submitted to the reference laboratories between 1992 and 1998. The median age of patients was 12 months (range: 6-48 months). Four of 5 had meningitis and bacteremia; 1 had purpura fulminans. Three isolates, representing 1 of 2 pulsed-field gel electrophoresis patterns, contained the IS1016-bexA deletion and were associated with particularly severe disease. CONCLUSIONS: We describe an unusual cluster of severe disease caused by H influenzae type a that resembles the clinical and epidemiologic features of H influenzae type b disease. Our data support the hypothesis that the IS1016-bexA deletion may identify more virulent strains of H influenzae. Haemophilus influenzae, epidemiology, virulence, serotyping, pathogenicity.

Original languageEnglish (US)
Pages (from-to)E18
JournalPediatrics
Volume108
Issue number1
StatePublished - Jul 2001

    Fingerprint

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

Cite this

Adderson, E. E., Byington, C. L., Spencer, L., Kimball, A., Hindiyeh, M., Carroll, K., Mottice, S., Korgenski, E. K., Christenson, J. C., & Pavia, A. T. (2001). Invasive serotype a Haemophilus influenzae infections with a virulence genotype resembling Haemophilus influenzae type b: emerging pathogen in the vaccine era? Pediatrics, 108(1), E18.