Abstract
Streptococcus pyogenes is an important human pathogen, which has recently gained recognition as an intracellular microorganism during the course of severe invasive infections such as necrotizing fasciitis. Although the surface anchored M protein has been identified as a pivotal factor affecting phagosomal maturation and S. pyogenes survival within macrophages, the overall transcriptional profile required for the pathogen to adapt and persist intracellularly is as of yet unknown. To address this, the gene expression profile of S. pyogenes within human macrophages was determined and compared to that of extracellular bacteria using customized microarrays and real-time qRT-PCR. In order to model the early phase of infection involving adaptation to the intracellular compartment, samples were collected 2h post-infection. Microarray analysis revealed that the expression of 145 streptococcal genes was significantly altered in the intracellular environment. The majority of differentially regulated genes were associated with metabolic and energy-dependent processes. Key up-regulated genes in early phase intracellular bacteria were ihk and irr, encoding a two-component gene regulatory system (TCS). Comparison of gene expression of selected genes at 2h and 6h post-infection revealed a dramatic shift in response regulators over time with a down-regulation of ihk/irr genes concurring with an up-regulation of the covR/S TCS. In re-infection assays, intracellular bacteria from the 6h time point exhibited significantly greater survival within macrophages than did bacteria collected at the 2h time point. An isogenic S. pyogenes mutant deficient in ihk/irr displayed significantly reduced bacterial counts when compared to wild-type bacteria following infection of macrophages. The findings illustrate how gene expression of S. pyogenes during the intracellular life cycle is fine-tuned by temporal expression of specific two-component systems.
Highlights
S. pyogenes is an important human pathogen causing an estimated 500,000 deaths yearly [1]
S. pyogenes is often found extracellulary in the host, we and others have demonstrated that the pathogen can reside intracellularly and circumvent bacterial killing in both human macrophages [5,6] and neutrophils [7,8]
All infections were done with the clinical S. pyogenes 5448 isolate of the M1T1 serotype, previously well-characterized with respect to intracellular trafficking and survival in macrophages [6]
Summary
S. pyogenes is an important human pathogen causing an estimated 500,000 deaths yearly [1]. S. pyogenes resides within phagocytic vacuoles that serve as safe-havens and niches for replication [6]; thereby contributing to bacterial persistence during invasive infection. In these phagocytic cells, the bacterial surface anchored M protein was recognized as an important factor contributing to S. pyogenes intracellular survival [6,7]. FasBCAX regulates fibronectin/ fibrinogen binding, hemolytic activity and streptokinase transcription [20], SptR/S has been shown to be important for the persistence of S. pyogenes in human saliva [21] and the Ihk/Irr was recently reported to be important for S. pyogenes resistance to neutrophil killing [22]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
