Direct Quantitative Transcript Analysis of the agr Regulon of Staphylococcus aureus during Human Infection in Comparison to the Expression Profile In Vitro
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Media type:
E-Article
Title:
Direct Quantitative Transcript Analysis of the agr Regulon of Staphylococcus aureus during Human Infection in Comparison to the Expression Profile In Vitro
Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Bacteria possess a repertoire of distinct regulatory systems promoting survival in disparate environments. Under in vitro conditions it was demonstrated for the human pathogen
<jats:italic>Staphylococcus aureus</jats:italic>
that the expression of most virulence factors is coordinated by the global regulator
<jats:italic>agr</jats:italic>
. To monitor bacterial gene regulation in the host, we developed a method for direct transcript analysis from clinical specimens. Quantification of specific transcripts was performed by competitive reverse transcription-PCR, and results were normalized against the constitutively expressed gene for gyrase (
<jats:italic>gyr</jats:italic>
). Using sputum from cystic fibrosis (CF) patients infected with
<jats:italic>S. aureus</jats:italic>
we examined the transcription of the effector molecule RNAIII of
<jats:italic>agr</jats:italic>
, of
<jats:italic>spa</jats:italic>
(protein A), generally repressed by
<jats:italic>agr</jats:italic>
, and of
<jats:italic>hla</jats:italic>
(alpha-toxin), generally activated by
<jats:italic>agr</jats:italic>
. In the CF lung RNAIII was expressed poorly, indicating an inactive
<jats:italic>agr</jats:italic>
in vivo. Despite the low level of RNAIII expression,
<jats:italic>spa</jats:italic>
was detectable only in minute amounts and an irregular transcription of
<jats:italic>hla</jats:italic>
was observed in all sputum samples. After subculturing of patient strains
<jats:italic>agr</jats:italic>
-deficient isolates and isolates with unusual expression profiles, i.e., not consistent with those obtained from prototypic strains, were observed. In conclusion, the
<jats:italic>agr</jats:italic>
activity seems to be nonessential in CF, and from the described expression pattern of
<jats:italic>spa</jats:italic>
and
<jats:italic>hla</jats:italic>
, other regulatory circuits aside from
<jats:italic>agr</jats:italic>
are postulated in vivo.
</jats:p>