Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
<jats:italic>Staphylococcus aureus</jats:italic>
superantigens (SAgs) are highly potent T cell mitogens. Antibodies against non-enterotoxin gene cluster (non-
<jats:italic>egc</jats:italic>
) SAgs are common in healthy adults, whereas neutralizing antibodies against
<jats:italic>egc</jats:italic>
SAgs are rare. We investigated the infecting
<jats:italic>S. aureus</jats:italic>
strains and the anti-SAg antibody response during
<jats:italic>S. aureus</jats:italic>
bacteremia (SAB). This prospective clinical study (
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="url" xlink:href="www.clinicaltrials.gov">www.clinicaltrials.gov</jats:ext-link>
,
<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="clintrialgov" xlink:href="NCT00548002">NCT00548002</jats:ext-link>
) included 43 injection drug users (IDUs) and 44 group-matched nonaddicts with SAB.
<jats:italic>spa</jats:italic>
genotypes and SAg gene patterns (multiplex PCR) of the
<jats:italic>S. aureus</jats:italic>
isolates were determined. The neutralizing capacities of sera obtained at the acute phase and the convalescent phase of SAB were tested against the SAg cocktail of the respective infecting strain and a panel of recombinant SAgs. The lineages CC59 and CC30 were more prevalent among bacteremia strains from IDUs than among strains from nonaddicts. SAg gene patterns in isolates from IDUs and nonaddicts were similar. At the acute phase of bacteremia, IDUs had more neutralizing antibodies against non-
<jats:italic>egc</jats:italic>
SAgs than did nonaddicts. Antibody titers frequently increased during infection. In contrast, there were no neutralizing antibodies against
<jats:italic>egc</jats:italic>
SAgs at disease onset and such antibodies were not induced by SAB. SAB triggers an antibody response only against non-
<jats:italic>egc</jats:italic>
SAgs. Preimmunization in IDU patients is probably due to previous exposure to the infecting strain.
</jats:p>