Development and efficacy of feed-based recombinant vaccine encoding the cell wall surface anchor family protein of Streptococcus agalactiae against streptococcosis in Oreochromis sp.

This study was carried out to determine the antibody responses and protective capacity of an inactivated recombinant vaccine expressing the cell wall surface anchor family protein of Streptococcus agalactiae following oral vaccination against streptococcosis in tilapia. Tilapia were vaccinated orally with 106 CFU/mL of the recombinant vaccine incorporated in feed (feed-based recombinant vaccine) (vaccinated group or Group 1), 106 CFU/mL of pET-32 Ek/LIC vector without cell wall surface anchor family protein (control group or Group 2), 106 CFU/mL of formalin-killed cells of S. agalactiae vaccine incorporated in feed was also prepared (feed-based vaccine) (vaccinated group or Group 3), and unvaccinated control group or Group 4 (fed with commercial pellets). During the course of study, serum, mucus and gut lavage fluid were collected to evaluate the antibody levels via enzyme-linked immunosorbent assay (ELISA). The results showed that tilapia immunized with the feed-based recombinant vaccine developed a strong and significantly (P < 0.05) higher IgM antibody response in serum, mucus and gut lavage fluid samples compared to groups 2, 3 and 4. Following heat intervenes and intraperitoneal challenge, the rate of survivors (RPS) was 70% for the vaccinated group, and 0% for the rest of the groups. Therefore, the study revealed that the feed-based recombinant vaccine significantly provides high protection against high dose challenge in heat stress environment and enhances the production of the mucosal and humoral immunity

Molecular characterization of Streptococcus agalactiae strains isolated from fishes in Malaysia

Aims: The aim of this study was to characterize Streptococcus agalactiae strains that were isolated from fishes in Malaysia using random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (REP-PCR) techniques. Methods and Results: A total of 181 strains of Strep. agalactiae isolated from red hybrid tilapia (Oreochromis sp.) and golden pompano (Trachinotus blochii) were characterized using RAPD and REP-PCR techniques. Both the fingerprinting techniques generated reproducible band patterns, differing in the number and molecular mass amplicons. The RAPD technique displayed greater discriminatory power by its production of more complex binding pattern and divided all the strains into 13 groups, compared to 9 by REP-PCR technique. Both techniques showed the availability to differentiate the genetic profiles of the strains according to their geographical location of origin. Three strains of Strep. agalactiae that were recovered from golden pompano showed a genetic dissimilarity from the strains isolated from red hybrid tilapia, while the strain of ATCC 27956 that recovered from bovine displayed a unique profile for both methods. Conclusions: Both techniques possess excellent discriminative capabilities and can be used as a rapid means of comparing Strep. agalactiae strains for future epidemiological investigation. Significance and Impact of the Study: Framework as the guideline in traceability of this disease and in the search for potential local vaccine candidates for streptococcosis in this country

Assessment of bacteria and water quality parameters in cage cultured Pangasius hypophthalmus in Temerloh, Pahang River, Malaysia

Pangasius hypophthalmus or famously known by local Malaysians as Patin Hitam is one of the most important sources of food in Malaysia. It is widely cultured in the Peninsular Malaysia especially in Pahang as Patin and is a popularly consumed freshwater fish. Global economic interest in the fish has increased its demand in the USA and Europe. However, high mortality due to bacterial and viral infections is the main problem that needs to be solved. Therefore, bacteria in P. hypophthalmus in Pahang is being focused with the factors connected to the prevalence of bacteria and virus in P. hypophthalmus. This research was conducted for two cycles (February-September 2016 and January-August 2017) in different farms in Temerloh, Pahang. Bacteria and virus samples were taken from three organs of Patin Hitam which are kidney, liver and spleen. Physical parameters for water quality were measured using a multiparameter probe sensor (YSI, USA) and chemical parameters were analysed with DR900 colorimeter (Hach, USA). Bacteria samples were identified using biochemical test kits, API 20NE and 20E, followed by confirmation of the bacteria using Polymerase Chain Reaction (PCR). Virus samples were identified using conventional PCR. There are several bacteria isolated throughout the culture period. The highest prevalence of Aeromonas hydrophila in Temerloh in the first cycle was in May 2016 (40%), however, was equally evident in four out of the seven months of the second cycle, which was in April, May, June and July 2017 (20%). There was a relationship between the prevalence of A. hydrophila and iron, nitrite and pH in the first cycle in Temerloh. However, there was no relationship in the second cycle. Significantly, these results could contribute to better treatment of fish disease and development of standard operating procedure of future fish culture for early disease prevention