Dataset Information

Experimental infection of Enterococcus faecalis in red tilapia (Oreochromis hybrid) revealed low pathogenicity to cause streptococcosis.

ABSTRACT:

Background

Streptococcosis, as a bacterial disease with broad tropism in fish and one of the causes of septicemia. Enterococcus faecalis is one of the causative agents of streptococcosis that can be isolated in tilapia.

Aim

This study was undertaken to complete the reporting gap on the pathogenicity profile and clinical symptoms of E. faecalis bacterial infection in red tilapia (Oreochromis hybrid). The study is expected to provide enriching information regarding recognizable clinical signs in the field that can lead to the diagnosis of streptococcosis caused by E. faecalis, especially in the Indonesian aquaculture environment.

Methods

The method used in this artificial infection study using red tilapia, which were divided into two types of route groups infection, namely intraperitoneal (IP) and peroral (PO) with bacterial concentrations given for each route of infection to be 2.1 × 10⁸ CFU ml^-1; 2.1 × 10⁷ CFU ml^- ¹; and 2.1 × 10⁶ CFU ml^-1. One group was given brain heart infusion broth media sterile as a non-infectious control. Clinical symptoms, changes in swimming habits and consuming feed, external and internal organ lesion, and leukocytes profile changes were observed during the observation period along 14 days to evaluate the infectious effect of each treated fish group. The lethal dose 50 (LD⁵⁰) was estimated with the Spearman-Kärber method. The evaluation of the leukocyte profile was performed to find leukocytosis as the clinical sign of infection.

Results

The results showed variations in clinical symptoms inflicted on fish through death or the moribund stage. The highest mortality occurred in the treatment group of 2.1 × 10⁸ CFU ml^-1 with the PO route. The bacterial concentration of 2.1 × 10⁷ CFU ml^-1 given either as PO or IP can cause mild infection symptoms but did not cause mortality. The LD₅₀ of the PO and IP route was obtained at 1.99 × 10⁸ CFU ml^-1 and 0.79 × 10⁸ CFU ml^-1, respectively. The total leukocytes in the infected fish group increased significantly (p < 0.05) by twofold when compared with the non-infectious group. The bacteria's discovery on the blood smear examination was taken from fresh dead fish or moribund fish in the treatment group of 2.1 × 10⁸ CFU ml^-1, for both PO and IP.

Conclusion

Enterococcus faecalis with low pathogenicity can lead to septicemia, characterized by a total increase in leukocytes, bacteria's discovery on the blood smear examination, and various clinical symptoms systemically found in the treated fish.

SUBMITTER: Rizkiantino R

PROVIDER: S-EPMC8288741 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Generally, the injection method is recommended as the best efficient method for vaccine applications in fish. However, labor-intensive and difficult injection for certain fish sizes is always considered as a limitation to aquatic animals. To demonstrate the effectiveness of a novel oral delivery system for the piscine vaccine with nano-delivery made from nano clay, halloysite nanotubes (HNTs) and their modified forms were loaded with killed vaccines, and we determined the ability of the system in releasing vaccines in a mimic digestive system. The efficaciousness of the oral piscine vaccine nano-delivery system was evaluated for its level of antibody production and for the level of disease prevention in tilapia. Herein, unmodified HNTs (H) and modified HNTs [HNT-Chitosan (HC), HNT-APTES (HA) and HNT-APTES-Chitosan (HAC)] successfully harbored streptococcal bivalent vaccine with inactivated S. agalactiae, designated as HF, HAF, HCF and HACF. The releasing of the loading antigens in the mimic digestive tract demonstrated a diverse pattern of protein releasing depending on the types of HNTs. Remarkably, HCF could properly release loading antigens with relevance to the increasing pH buffer. The oral vaccines revealed the greatest elevation of specific antibodies to S. agalactiae serotype Ia in HCF orally administered fish and to some extent in serotype III. The efficacy of streptococcal disease protection was determined by continually feeding with HF-, HAF-, HCF- and HACF-coated feed pellets for 7 days in the 1st and 3rd week. HCF showed significant RPS (75.00 ± 10.83%) among the other tested groups. Interestingly, the HCF-treated group exhibited noticeable efficacy similar to the bivalent-vaccine-injected group (RPS 81.25 ± 0.00%). This novel nano-delivery system for the fish vaccine was successfully developed and exhibited appropriated immune stimulation and promised disease prevention through oral administration. This delivery system can greatly support animals' immune stimulation, which conquers the limitation in vaccine applications in aquaculture systems. Moreover, this delivery system can be applied to carrying diverse types of biologics, including DNA, RNA and subunit protein vaccines.