Aeromonas hydrophila induction method in adult zebrafish (Danio rerio) as animal infection models.

Background and Aim: Zebrafish are frequently used as model organisms in scientific research as their genes mirror those of humans. Aeromonas hydrophila bacteria can infect humans and animals, mainly fish. This study aimed to identify the concentration and route of A. hydrophila infection in adult zebrafish. Zebrafish had been used as a challenge test by analyzing their hematological profiles, blood glucose levels, and survival rates. Materials and Methods: Induction of cell supernatant free (CSF) from A. hydrophila bacteria in adult zebrafish was carried out via bath immersion (BI), intraperitoneal injection (IPI), intramuscular injection (IMI), and healthy zebrafish as a control (C). The bacterial concentrations were 107, 109, and 1011 colony-forming units (CFU)/mL. At 24 h post-infection, the outcomes of infection were evaluated based on survival rates, hematological profiles, and blood glucose levels. A one-way analysis of variance with a confidence level of 95% was employed to examine the data. Results: In the BI, IPI, and IMI treatment groups, the survival rate of the fish reached a peak of 100%, 22%-100%, and 16%-63%, respectively, compared with the injection technique. In the IMI2 group, a 109 CFU/mL bacterial concentration was determined to correspond to the lethal dosage 50. All infection groups had lower erythrocyte and hemoglobin counts but higher leukocyte counts than the control group. The blood sugar levels of the healthy and infected groups were not significantly different. Conclusion: The route of A. hydrophila infection through Intramuscular injection with a concentration of 109 CFU/mL indicated a high performance compared to other techniques. This method could be developed as a reproducible challenge test.

Methanol extract of Black soldier fly (Hermetia illucens) prepupae against Aeromonas and Staphylococcus aureus bacteria in vitro and in silico.

Background: Staphylococcus and Aeromonas bacteria are pathogens in humans and animals. The therapy disrupts the virulence structure of the bacteria, resulting in bacterial death. Currently, chemical drugs have resulted in many resistant bacteria, so it is necessary to find alternative natural materials that are not toxic and do not quickly induce resistance. Aims: This study aimed to analyze the potential of methanol extract from Black soldier fly (BSF) prepupae as an antibacterial agent against Staphylococcus aureus and Aeromonas through in silico and in vitro tests. Methods: The BSF prepupae methanol extract was analyzed for protein and fatty acid contents. Disc diffusion method, minimal inhibitory concentration, and minimum bactericidal concentration test were used for in vitro tests against Staphylococcis and Aeromonas. Molecular docking of the active ingredients (defensin, chitin, and chitosan as well as fatty acids) in BSF was downloaded from the NCBI database and docked by the Hex Cuda version 8.0 program with Correlation type parameters Shape + Electro and Grid Dimension version 0.6. Docking results were analyzed using the Discovery Studio program version 21.1.1. Results: The highest fatty acid contents in the extract were palmitic acid and myristic acid. Methanol extract from BSF prepupae acted as a bactericidal agent against S. aureus at a concentration of 320 mg/ml, in contrast to Aeromonas, which still showed bacterial growth. The results of the in silico test showed that defensin-aerolysin and defensin-hemolysin was bound to the same active site area. However, the amount of binding energy produced by 69-Defensin-83-aerolysin was higher than all defensin types in BSF against Aeromonas. Chitin and chitosan showed a bond on the active site of aerolysin and hemolysin, but chitosan had a stronger bond than chitin. In silico study also showed the strongest binding affinity of BSF fatty acids to isoleucyl-tRNA synthetase of S. aureus. Conclusion: The study showed that methanol extract from BSF prepupae had potential capability as an antibacterial agent against S. aureus than Aeromonas in vitro and in silico.

Effect of Nauclea subdita (Korth.) Steud. leaf extract on hematological and histopathological changes in liver and kidney of striped catfish infected by Aeromonas hydrophila.

AIM: The present study was conducted to investigate the efficacy of different doses of Bangkal (Nauclea subdita) leaf extract on hematological and histological changes in kidney and liver of catfish (Pangasius hypophthalmus) infected by Aeromonas hydrophila. MATERIALS AND METHODS: Catfish were experimentally infected with A. hydrophila at a dose of 108 cells/mL through intraperitoneal injection, and the hematological and histological changes in the kidney and liver of catfish against the pathogen were observed. RESULTS: Not all concentrations of N. subdita caused a toxic effect in striped catfish. The clinical symptoms of catfish after infection with A. hydrophila and treatment with N. subdita leaf extract included morphological and behavioral changes. N. subdita leaf extract reduced mortality caused by A. hydrophila. Treatment with N. subdita leaf extract was effective in reducing the inflammation by decreasing the activity of neutrophils, monocytes, and lymphocytes. The Hb and Ht levels of catfish significantly decreased after exposure to 108 cells/mL of A. hydrophila and increased significantly after N. subdita treatment. Necrosis percentages in the kidney and liver also decrease after N. subdita treatment. CONCLUSION: The results indicate that N. subdita leaf extract stimulates the immunity and increases the resistance of catfish to A. hydrophila. N. subdita leaf extract may be used as a potential source for future drug development and food applications.

Histopathology of gill, muscle, intestine, kidney, and liver on Myxobolus sp.-infected Koi carp (Cyprinus carpio).

This research aims to investigate the clinical symptoms of Myxobolus sp.-infected Koi carp (Cyprinus carpio) and to observe fish histopathology including histological alteration in the intestine, kidney, and liver organs. Descriptive method was employed in this research. The fish sample was obtained from Fish Farmer Group at Nglegok Village in Blitar City. The main observed parameters were the alteration of intestine, kidney, and liver of Koi infected with Myxobolus sp. parasite. The observation result of the histopathology of the parasite-infected fish indicated that necrosis and cyst occurred in the intestine. Necrosis also occurred in kidney, while hyaline degeneration occurred in tubule cells. Furthermore, necrosis and inflammation were also found in liver. It is obvious from the result that Myxobolus sp. infection resulted in the damage of Koi carp vital organs.