Detection of virulence factors of South African Lactococcus garvieae isolated from rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract

Lactococcus garvieae is a Gram-positive bacterium that causes mortalities in freshwater and marine fish worldwide and therefore results in severe economic losses in the aquaculture industry. Apart from the apparent integral role of the exopolysaccharide (EPS) capsule in pathogenesis, factors associated with virulence of this bacterium are poorly understood. However, recent studies have indicated that the ability of L. garvieae to cause disease does not depend on the presence of the EPS capsule. Lack of knowledge of virulence factors, pathogenesis and serology of L. garvieae is an impediment to the development of effective typing methods and control measures. This study, therefore, aimed to detect the presence of EPS capsules and other putative virulence factors in South African L. garvieae fish pathogenic isolates and a non-virulent isolate, and to identify possible candidates for subunit vaccine development. No indication of the presence of the EPS capsule was detected by negative staining or amplification of the EPS biosynthesis gene cluster in the virulent isolates or the avirulent strain, discrediting the notion that the EPS capsule is the sole determinant of virulence. However, a set of putative virulence factor genes was detected in all isolates, and candidates for subunit vaccine development (enolase, lactate dehydrogenase phosphoenolpyruvate-protein phosphotransferase) were identified by identification of extracellular proteins of virulent strains.

First identification, molecular characterization, and pathogenicity assessment ofLactococcus garvieaeisolated from cultured pompano in Taiwan

“…Previously, it was believed that pathogenic L. garvieae isolates possessed capsules (KG−/agglutinating), whereas non‐capsulated isolates (KG+/non‐agglutinating) were non‐pathogenic (Barnes & Ellis, 2004; Ooyama et al, 2006). However, recent isolates have proven this assumption incorrect, as non‐capsulated strains have also been found to be virulent in fish (Meyburgh et al, 2018; Shahi et al, 2018). Multiplex PCR confirmed the absence of a capsule gene cluster.…”

A review of the implications of Lactic Acid Bacteria and Bifidobacteria in human and animal diseases

“…This bacterium was resistant to multiple antibiotics. Eiji et al, (68) reported virulence genes in L. garvieae from different sources using comparative genomic analysis and recently, this bacterium isolated from diseased rainbow trout was reported to have carried important virulence genes such as haemolysins 1,2,3, NADH oxidase, phosphoglucomutase, adhesins, superoxide dismutase, enolase, among others (69,70).…”

Comparative Genomic Analyses of Lactococcus garvieae Isolated from Bovine Mastitis in China

“…Bacterial pathogenicity is primarily determined by virulence genes: some facilitate adhesion and invasion, whereas antimicrobial resistance (AMR), particularly multidrug resistance, is an important threat to public health ( 21 ). For L. garvieae , several virulence genes and antimicrobial resistance genes were identified using traditional methods (e.g., PCR) targeted at specific virulence genes ( 22 – 24 ). However, a comprehensive profiling of its virulence and antimicrobial resistance genes is lacking.…”