First identification and characterization of Streptococcus iniae obtained from tilapia (Oreochromis aureus) farmed in Mexico

Abstract

This is the first study to isolate, identify and characterize Streptococcus iniae as the causative disease agent in two tilapia (Oreochromis aureus) populations. The populations were geographically isolated, of distinct origins, and did not share water sources. Affected fish showed various external (e.g., exophthalmia and cachexia, among others) and internal (e.g., granulomatous septicaemia and interstitial nephritis, among others) signs. All internal organ samples produced pure cultures, two of which (one from each farm, termed S-1 and S-2) were subjected to biochemical, PCR and 16S rRNA sequencing (99.5% similarity) analyses, confirming S. iniae identification. The two isolates presented genetic homogeneity regardless of technique (i.e., RAPD, REP-PCR and ERIC-PCR analyses). Pathogenic potentials were assessed through intraperitoneal injection challenges in rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio). Rainbow trout mortalities were respectively 40% and 70% at 10 and 10 CFU per fish with the S-1 isolate, while 100% mortality rates were recorded in zebrafish at 10 and 10 CFU per fish with the S-2 isolate. The obtained data clearly indicate a relationship between intensified aquaculture activities in Mexico and new disease appearances. Future studies should establish clinical significances for the tilapia industry.

In vitro assessment of potential probiotic characteristics of indigenous Lactococcus lactis and Weissella oryzae isolates from rainbow trout ( Oncorhynchus mykiss Walbaum)

“…(2000) reported for the first time the disease in a rainbow trout farm in Mazanderan Province in North of Iran. This infection has also been reported in other species such as Tilapia ( Oreochromis aureus ) and Siberian sturgeon ( Acipenser baerii ) (Deng et al 2017; Ortega et al 2018). Moreover this infection has been recognized as a zoonotic agent, causing human disease (Ortega et al 2018).…”

“…This infection has also been reported in other species such as Tilapia ( Oreochromis aureus ) and Siberian sturgeon ( Acipenser baerii ) (Deng et al 2017; Ortega et al 2018). Moreover this infection has been recognized as a zoonotic agent, causing human disease (Ortega et al 2018). In fish, the clinical symptoms include lethargy, swimming erratically and exophthalmia (Soltani et al 2005).…”

Phenotypic and genotypic characterization of Streptococcus spp. isolated from tilapia (Oreochromis spp.) cultured in river‐based cage and earthen ponds in Northern Thailand

“…Different among sections of the river and in the sources of the fry may be responsible for the variation in phenotype. Biochemical methods are not adequate for the identification of Streptococcus spp., especially for S. iniae (Ortega et al, ). Serological tests showed no agglutination when S. iniae was tested for the Lancefield grouping.…”

“…Globally, streptococcosis has become one of the most serious aquatic diseases, resulting in massive mortality (up to 50%) and economic losses in the aquaculture industry. Streptococcus agalactiae (GBS) and Streptococcus iniae ( S. iniae ) have been recognized as the two primary species responsible for economic losses in tilapia (Kayansamruaj, Pirarat, Katagiri, Hirono, & Rodkhum, ; Ortega et al, ). Outbreaks of GBS and S. iniae in tilapia have been reported in various countries especially in tropical regions including Thailand, where it represents a major threat to the tilapia industry (Jantrakajorn, Maisak, & Wongtavatchai, ).…”

Isolation characterization, virulence potential ofWeissella cetiresponsible for weissellosis outbreak in rainbow trout (Oncorhynchus mykiss) cultured in Mexico

“…Commercial farming began in the early 1970s and now comprises 984 commercial farms and 170 subsistence farms (Ortega & Valladares, ). Intensified aquaculture farming is provoking the appearance of diseases, such as the recently confirmed francisellosis (Ortega et al., ) and streptococcosis in tilapia ( Oreochromis aureus ) (Ortega et al., ), as well as rainbow trout fry syndrome ( Flavobacterium psychrophilum ) (Castillo et al., ). Continuing this trend, this study is the first report on W. ceti ‐associated septicaemia processes in Mexican‐farmed rainbow trout.…”