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Infection and Immunity, March 2000, p. 1304-1311, Vol. 68, No. 3
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Direct Quantitative Transcript Analysis of the agr Regulon of Staphylococcus aureus during Human Infection in Comparison to the Expression Profile In Vitro

Christiane Goerke,1 Silvia Campana,2 Manfred G. Bayer,3 Gerd Döring,1 Konrad Botzenhart,1 and Christiane Wolz1,*

Allgemeine Hygiene und Umwelthygiene, Universität Tübingen, Tübingen,1 and 4base Lab GmbH Advanced Molecular Analysis, Reutlingen,3 Germany, and Dipartimento di Pediatria "Cesare Cocci," Ospedale Meyer, Florence, Italy2

Received 25 October 1999/Returned for modification 16 November 1999/Accepted 16 December 1999

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.

* Corresponding author. Mailing address: Allg. Hygiene und Umwelthygiene, Universität Tübingen, Wilhelmstraße 31, 72074 Tübingen, Germany. Phone: 49-7071-2980187. Fax: 49-7071-293011. E-mail: christiane.wolz{at}uni-tuebingen.de.

Infection and Immunity, March 2000, p. 1304-1311, Vol. 68, No. 3
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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