期刊名称：Annals of Agricultural and Environmental Medicine
印刷版ISSN：1232-1966
电子版ISSN：1898-2263
出版年度：2018
卷号：25
期号：1
页码：186-203
DOI：10.26444/aaem/85651
出版社：Institute of Agricultural Medicine in Lublin
摘要：Streptococcus suis is a re-emerging zoonotic pathogen that may cause severe disease, mostly meningitis, in pigs and in humanshaving occupational contact with pigs and pork, such as farmers, slaughterhose workers and butchers. The first stage of thepathogenic process, similar in pigs and humans, is adherence to and colonisation of mucosal and/or epithelial surface(s) ofthe host. The second stage is invasion into deeper tissue and extracellular translocation of bacterium in the bloodstream,either free in circulation or attached to the surface of monocytes. If S. suis present in blood fails to cause fatal septicaemia,it is able to progress into the third stage comprising penetration into host’s organs, mostly by crossing the blood-brainbarrier and/or blood–cerebrospinal fluid barrier to gain access to the central nervous system (CNS) and cause meningitis.The fourth stage is inflammation that plays a key role in the pathogenesisof both systemic and CNS infections caused byS. suis. The pathogen may induce the overproduction of pro-inflammatory cytokines that cause septic shock and/or therecruitment and activation of different leukocyte populations, causing acute inflammation of the CNS. Streptococcus suiscan also evoke – through activation of microglial cells, astrocytes and possibly other cell types – a fulminant inflammatoryreaction of the brain which leads to intracranial complications, including brain oedema, increased intracranial pressure,cerebrovascular insults, and deafness, as a result of cochlear sepsis.In all stages of the pathogenic process, S. suis interacts with many types of immunocompetent host’s cells, such aspolymorphonuclear leukocytes, mononuclear macrophages, lymphocytes, dendritic cells and microglia, using a rangeof versatile virulence factors for evasion of the innate and adaptive immune defence of the host, and for overcomingenvironmental stress. It is estimated that S. suis produces more than 100 different virulence factors that could be classifiedinto 4 groups: surface components or secreted elements, enzymes, transcription factors or regulatory systems andtransporter factors or secretion systems. A major virulence factor is capsular polysaccharide (CPS) that protects bacteriafrom phagocytosis. However, it hampers adhesion to and invasion of host’s cells, release of inflammatory cytokines andformation of the resistant biofilm which, in many cases, is vital for the persistence of bacteria. It has been demonstrated thatthe arising by mutation unencapsulated S. suis clones, which are more successful in penetration to and propagation withinthe host’s cells, may coexist in the organism of a single host together with those that are encapsulated. Both ‘complementary’clones assist each other in the successful colonization of host’s tissues and persistence therein.S. suis has an open pan-genome characterized by a frequent gene transfer and a large diversity. Of the genetic determinantsof S. suis pathogenicity, the most important are pathogenicity islands (PAI), in particular, a novel DNA segment of 89 kblength with evident pathogenic traits that has been designated as 89K PAI. It has been estimated that more than one-thirdof the S. suis virulence factors is associated with this PAI. It has been proved that the virulent S. suis strains possess smallergenomes, compared to avirulent ones, but more genes associated with virulence. Overall, the evolution of the species mostprobably aims towards increased pathogenicity, and hence the most significant task of the current research is an elaborationof a vaccine, efficient both for humans and pigs.
关键词：Streptococcus suis; pathogenesis; infection stages; interaction with host cells and tissues; virulence factors; genomic;determinants of pathogenicity; biofilm formation
