Direct Quantitative Transcript Analysis of the agr Regulon of Staphylococcus aureus during Human Infection in Comparison to the Expression Profile In Vitro
Lung Diseases
Staphylococcus aureus
0303 health sciences
Cystic Fibrosis
Reverse Transcriptase Polymerase Chain Reaction
Bacterial Toxins
Sputum
Staphylococcal Infections
Regulon
3. Good health
Hemolysin Proteins
03 medical and health sciences
Bacterial Proteins
Chronic Disease
Trans-Activators
Humans
RNA, Messenger
Staphylococcal Protein A
Transcription Factors
DOI:
10.1128/iai.68.3.1304-1311.2000
Publication Date:
2002-07-27T10:01:19Z
AUTHORS (6)
ABSTRACT
ABSTRACT
Bacteria possess a repertoire of distinct regulatory systems promoting survival in disparate environments. Under in vitro conditions it was demonstrated for the human pathogen
Staphylococcus aureus
that the expression of most virulence factors is coordinated by the global regulator
agr
. 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 (
gyr
). Using sputum from cystic fibrosis (CF) patients infected with
S. aureus
we examined the transcription of the effector molecule RNAIII of
agr
, of
spa
(protein A), generally repressed by
agr
, and of
hla
(alpha-toxin), generally activated by
agr
. In the CF lung RNAIII was expressed poorly, indicating an inactive
agr
in vivo. Despite the low level of RNAIII expression,
spa
was detectable only in minute amounts and an irregular transcription of
hla
was observed in all sputum samples. After subculturing of patient strains
agr
-deficient isolates and isolates with unusual expression profiles, i.e., not consistent with those obtained from prototypic strains, were observed. In conclusion, the
agr
activity seems to be nonessential in CF, and from the described expression pattern of
spa
and
hla
, other regulatory circuits aside from
agr
are postulated in vivo.
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