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Molecular characterization of four Haemophilus influenzae serotype a strains isolated from patients in Quebec, Canada

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Four epidemiologically unrelated Haemophilus influenzae serotype a (Hia) strains from patients in Quebec, Canada, were characterized and found to represent 3 distinct groups. One isolate, found to be biotype I and sequence type (ST)-62 by multilocus sequence typing, was shown to possess the copper- and zinc-containing superoxide dismutase gene, sodC, and was suspected to belong to clonal division II. The other 3 isolates were classified as clonal division I based on the absence of the sodC gene. Among the 3 sodC-negative Hia strains, 2 were biotype II and had related STs (ST-23 and ST-403) and highly similar DNA fingerprints, similar to a group of previously described Hia isolates causing invasive disease in Manitoba, Canada. The remaining sodC-negative strain belonged to biotype I and ST-4 and shared no common allele with ST-23, ST-403, or ST-62. This isolate also possessed the IS1016-bexA partial deletion, which is often associated with increased virulence. Despite the small number of isolates used in this study, our finding of 3 distinct groups shows the existence of a potential genetic diversity not previously described for Hia. Whether this genetic diversity is related to the severity and epidemiology of Hia disease requires further studies.

Quatre souches de Haemophilus influenzae de sérotype a (Hia), non reliées d’un point de vue épidémiologique et isolées de patients du Quebec, Canada, ont été caractérisées et représentaient 3 groupes distincts. Un isolat de biotype I et de type 62 selon le typage de séquence multi-locus (ST-62) possédait le gène codant la superoxyde dismutase à cuivre et zinc, sodC, et appartenait vraisemblablement à la division clonale II. Les 3 autres isolats ont été classés parmi la division I sur la base de l’absence du gène sodC. Parmi les 3 Hia sans sodC, 2 appartenaient au biotype II et à des ST reliés (ST-23 et ST-403), avec des empreintes d’ADN hautement similaires, ressemblant ainsi à un groupe d’isolats de Hia invasifs décrit précédemment au Manitoba, Canada. L’autre souche sans sodC appartenait au biotype 1 et au ST-4, et ne partageait aucune allèle avec ST-23, ST-403 ou ST-62. Cet isolat présentait aussi une délétion partielle IS1016-bexA, souvent associée avec une virulence accrue. Malgré le faible nombre d’isolats utilisés dans cette étude, la présence de trois groupes distincts révèle l’existence d’une diversité génétique potentielle jamais décrite chez Hia. Des études additionnelles sont requises afin de déterminer si la diversité génétique est reliée à la sévérité et à l’épidémiologie des infections à Hia.

Document Type: Research Article

Publication date: October 1, 2007

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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