Cellular interactions of covR/S mutant group A Streptococci

Transcriptome and metabolome profiling to elucidate the mechanism underlying the poor growth of Streptococcus suis serotype 2 after orphan response regulator CovR deletion

The deletion of orphan response regulator CovR reduces the growth rate of Streptococcus suis serotype 2 (S. suis 2). In this study, metabolome and transcriptome profiling were performed to study the mechanisms underlying the poor growth of S. suis 2 caused by the deletion of orphan response regulator CovR. By comparing S. suis 2 (ΔcovR) and S. suis 2 (SC19), 146 differentially accumulated metabolites (upregulated: 83 and downregulated: 63) and 141 differentially expressed genes (upregulated: 86 and downregulated: 55) were identified. Metabolome and functional annotation analysis revealed that the growth of ΔcovR was inhibited by the imbalance aminoacyl tRNA biosynthesis (the low contents of L-lysine, L-aspartic acid, L-glutamine, and L-glutamic acid, and the high content of L-methionine). These results provide a new insight into the underlying poor growth of S. suis 2 caused by the deletion of orphan response regulator CovR. Metabolites and candidate genes regulated by the orphan response regulator CovR and involved in the growth of S. suis 2 were reported in this study.

Inflammasome activation and IL-1β signalling in group A Streptococcus disease

Group A Streptococcus (GAS) is a Gram-positive bacterial pathogen that causes significant morbidity and mortality worldwide. Recent clinical evidence suggests that the inflammatory marker interleukin-1β (IL-1β) plays an important role in GAS disease progression, and presents a potential target for therapeutic intervention. Interaction with GAS activates the host inflammasome pathway to stimulate production and secretion of IL-1β, but GAS can also stimulate IL-1β production in an inflammasome-independent manner. This review highlights progress that has been made in understanding the importance of host cell inflammasomes and IL-1 signalling in GAS disease, and explores challenges and unsolved problems in this host-pathogen interaction. TAKE AWAY: Inflammasome signalling during GAS infection is an emerging field of research. GAS modulates the NLRP3 inflammasome pathway through multiple mechanisms. SpeB contributes to IL-1β production independently of the inflammasome pathway. IL-1β signalling can be host-protective, but also drive severe GAS disease.

A current review of pathogenicity determinants of Streptococcus sp

The genus Streptococcus comprises important pathogens, many of them are part of the human or animal microbiota. Advances in molecular genetics, taxonomic approaches and phylogenomic studies have led to the establishment of at least 100 species that have a severe impact on human health and are responsible for substantial economic losses to agriculture. The infectivity of the pathogens is linked to cell-surface components and/or secreted virulence factors. Bacteria have evolved sophisticated and multifaceted adaptation strategies to the host environment, including biofilm formation, survival within professional phagocytes, escape the host immune response, amongst others. This review focuses on virulence mechanism and zoonotic potential of Streptococcus species from pyogenic (S. agalactiae, S. pyogenes) and mitis groups (S. pneumoniae).

Rheumatic heart disease: A review of the current status of global research activity

Rheumatic heart disease (RHD) is a serious and long-term consequence of acute rheumatic fever (ARF), an autoimmune sequela of a mucosal infection by Streptococcus pyogenes (Group A Streptococcus, Strep A). The pathogenesis of ARF and RHD is complex and not fully understood but involves host and bacterial factors, molecular mimicry, and aberrant host innate and adaptive immune responses that result in loss of self-tolerance and subsequent cross-reactivity with host tissues. RHD is entirely preventable yet claims an estimated 320 000 lives annually. The major burden of disease is carried by developing nations and Indigenous populations within developed nations, including Australia. This review will focus on the epidemiology, pathogenesis and treatment of ARF and RHD in Australia, where: streptococcal pyoderma, rather than streptococcal pharyngitis, and Group C and Group G Streptococcus, have been implicated as antecedents to ARF; the rates of RHD in remote Indigenous communities are persistently among the highest in the world; government register-based programs coordinate disease screening and delivery of prophylaxis with variable success; and researchers are making significant progress in the development of a broad-spectrum vaccine against Strep A.

Microbes and Infection turns 20

The journal Microbes and Infection is celebrating its vigintennial anniversary and has reunited for this occasion two dozen reviews illustrating achievements of the past as well as future challenges in the field of infectious diseases. From top-notch vaccine development strategies, to high-throughput powered analysis of complex host-pathogen interactions, to innovative therapeutic designs, this issue covers the entire spectrum of pathogens and areas of their confrontation with the host.