Abstract
Streptococcus agalactiae, often referred to as group B streptococci (GBS), is a severe pathogen that can infect humans as well as other animals, including tilapia, which is extremely popular in commercial aquaculture. This pathogen causes enormous pecuniary loss, and typical symptoms of streptococcosis—the disease caused by S. agalactiae—include abnormal behavior, exophthalmos, and meningitis, among others. Multiple studies have examined virulence factors associated with S. agalactiae infection, and vaccines were explored, including studies of subunit vaccines. Known virulence factors include capsular polysaccharide (CPS), hemolysin, Christie-Atkins-Munch-Peterson (CAMP) factor, hyaluronidase (HAase), superoxide dismutase (SOD), and serine-threonine protein kinase (STPK), and effective vaccine antigens reported to date include GapA, Sip, OCT, PGK, FbsA, and EF-Tu. In this review, I summarize findings from several studies about the etiology, pathology, virulence factors, and vaccine prospects for S. agalactiae. I end by considering which research areas are likely to yield success in the prevention and treatment of tilapia streptococcosis.
Highlights
Streptococcus agalactiae (S. agalactiae), commonly referred to as group B streptococcus (GBS), is a severe pathogen that can infect humans and a diversity of other animals, including reptiles, frogs, bovines, fish, and pigs, among others [1,2,3].Streptococcosis—the disorder caused by group B streptococci (GBS) infection—is a major obstacle faced by the tilapia aquaculture industry: in 2011, streptococcosis caused the loss of $40 million in the tilapia industry in China, owing to high morbidity and mortality, which can reach up to80% in outbreaks [4,5]
Streptococcosis—the disorder caused by GBS infection—is a major obstacle faced by the tilapia aquaculture industry: in 2011, streptococcosis caused the loss of $40 million in the tilapia industry in China, owing to high morbidity and mortality, which can reach up to
Besides the aforementioned virulence factors, there are other virulence factors, which have not been experimentally confirmed in tilapia GBS infections, but, which have been widely studied in mammalian GBS infections, including, for example, fibrinogen receptor (FbsA, FbsB and FbsC) [62], superoxide dismutase (SOD), serine-threonine protein kinase (STPK), C5a peptidase [14], serine-rich repeat glycoproteins [63], β-hemolysin/cytolysin [64], pili [65], proteins Cα [66], neul [67], and α-like protein (Alp) [68], among others
Summary
Streptococcus agalactiae (S. agalactiae), commonly referred to as group B streptococcus (GBS), is a severe pathogen that can infect humans and a diversity of other animals, including reptiles, frogs, bovines, fish (including tilapia), and pigs, among others [1,2,3]. Among GBS virulence factors, a large number are known to affect adherence and invasion of host cells, as well as evasion of host immunity [7]. Studies of GBS isolated from humans have split virulence factors into pore-forming toxins, factors for immune evasion, resistance to antimicrobial peptides (AMPs), host-cell adherence and invasion, and other virulence factors [7,8,9]. GBS can encode several virulence factors that promote immune evasion. The adherent factors, such as fibrinogen-binding protein (FbsA/B/C), laminin-binding protein (Lmb), the immunogenic bacterial adhesin (BibA), Pili (PilA/B/C), 4.0/). Vaccines—which induce adaptive immune responses—can overcome some of these challenges Given their potent efficacy, the development of vaccines for preventing GBS outbreaks has been widely investigated, including inactivated vaccines, attenuated vaccines, subunit vaccines, and DNA vaccines
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