Initial steps of the pathogenesis of the infection caused by Streptococcus suis: fighting against nonspecific defenses

Abstract

Edited by Wilhelm JustInteractions between a bacterial pathogen and its potentially susceptible host are initiated with the colonization step. During respiratory/oral infection, the pathogens must compete with the normal microflora, resist defense mechanisms of the local mucosal immunity, and finally reach, adhere, and breach the mucosal epithelial cell barrier in order to induce invasive disease. This is the case during infection by the swine and zoonotic pathogen Streptococcus suis, which is able to counteract mucosal barriers to induce severe meningitis and sepsis in swine and in humans. The initial steps of the pathogenesis of S. suis infection has been a neglected area of research, overshadowed by studies on the systemic and central nervous phases of the disease. In this Review article, we provide for the first time, an exclusive focus on S. suis colonization and the potential mechanisms involved in S. suis establishment at the mucosa, as well as the mechanisms regulating mucosal barrier breakdown. The role of mucosal immunity is also addressed. Finally, we demystify the extensive list of putative adhesins and virulence factors reported to be involved in the initial steps of pathogenesis by S. suis.

Transcriptomic Analysis Reveals Selective Metabolic Adaptation of Streptococcus suis to Porcine Blood and Cerebrospinal Fluid

“…In healthy pigs, S. suis is a frequent commensal of the upper respiratory tract. Thus, colonization and interaction of S. suis with epithelial cells is proposed to be the first step for invasive infection [3]. After breaching of the epithelial barrier, streptococci enter the bloodstream and disseminate within the host [4,5].…”

Porcine Dendritic Cells as an In Vitro Model to Assess the Immunological Behaviour of Streptococcus suis Subunit Vaccine Formulations and the Polarizing Effect of Adjuvants

“…The pathogenesis of S. suis infection is not fully understood. In swine, the main port of entry for S. suis is the upper respiratory tract [7]. Subsequently, this pathogen can overthrow the immune system, through an arsenal of virulence factors, including the CPS [8], to cause acute septicemia that may lead to septic shock or different clinical outcomes depending on the colonized organ via mechanisms that are only partially elucidated to date [9].…”

IgM cleavage by Streptococcus suis reduces IgM bound to the bacterial surface and is a novel complement evasion mechanism

“…S. suis colonizes the mucosal surfaces of healthy pigs but can lead to invasive disease, mainly in growing piglets of approximately five to ten weeks of age [2,3]. These piglets might develop suppurative meningitis, arthritis, endocarditis, serositis and septicemia upon S. suis infection [1].…”