Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
The
<jats:italic>sodC</jats:italic>
gene has been reported to be a useful marker for differentiating nontypeable (NT)
<jats:italic>Haemophilus influenzae</jats:italic>
from
<jats:italic>Haemophilus haemolyticus</jats:italic>
in respiratory-tract samples, but discrepancies exist as to the prevalence of
<jats:italic>sodC</jats:italic>
in NT
<jats:italic>H. influenzae</jats:italic>
. Therefore, we used a microarray-based, “library-on-a-slide” method to differentiate the species and found that 21 of 169 (12.4%) NT
<jats:italic>H. influenzae</jats:italic>
strains and all 110 (100%)
<jats:italic>H. haemolyticus</jats:italic>
strains possessed the
<jats:italic>sodC</jats:italic>
gene. Multilocus sequence analysis confirmed that the 21 NT
<jats:italic>H. influenzae</jats:italic>
strains were
<jats:italic>H. influenzae</jats:italic>
and not
<jats:italic>H. haemolyticus</jats:italic>
. An inactive
<jats:italic>sodC</jats:italic>
gene has been reported in encapsulated
<jats:italic>H. influenzae</jats:italic>
strains belonging to phylogenetic division II. Capsule-specific Southern hybridization and PCR and a lack of copper/zinc-cofactored superoxide dismutase (CuZnSOD) expression indicated that 6 of the 21
<jats:italic>sodC</jats:italic>
-containing NT
<jats:italic>H. influenzae</jats:italic>
strains in our study were likely capsule-deficient mutants belonging to phylogenetic division II. DNA sequence comparisons of the 21
<jats:italic>H. influenzae sodC</jats:italic>
genes with
<jats:italic>sodC</jats:italic>
from
<jats:italic>H. haemolyticus</jats:italic>
or encapsulated
<jats:italic>H. influenzae</jats:italic>
demonstrated that the
<jats:italic>sodC</jats:italic>
genes of the six
<jats:italic>H. influenzae</jats:italic>
capsule-deficient mutants were, on average, 99% identical to
<jats:italic>sodC</jats:italic>
from encapsulated
<jats:italic>H. influenzae</jats:italic>
but only 85% identical to
<jats:italic>sodC</jats:italic>
from
<jats:italic>H. haemolyticus</jats:italic>
. The
<jats:italic>sodC</jats:italic>
genes from 2/15 NT
<jats:italic>H. influenzae</jats:italic>
strains were similarly more closely related to
<jats:italic>sodC</jats:italic>
from encapsulated strains, while
<jats:italic>sodC</jats:italic>
genes from 13 NT
<jats:italic>H. influenzae</jats:italic>
strains were almost 95% identical to
<jats:italic>sodC</jats:italic>
genes from
<jats:italic>H. haemolyticus</jats:italic>
, suggesting the possibility of interspecies recombination in these strains. In summary, this study demonstrates that
<jats:italic>sodC</jats:italic>
is not completely absent (9.2%) in true NT
<jats:italic>H. influenzae</jats:italic>
strains.
</jats:p>