Lesser wax worm, Achroia grisella larvae as an animal model for Escherichia coli infection

Erriah, Pirasannah (2021) Lesser wax worm, Achroia grisella larvae as an animal model for Escherichia coli infection. [Project Paper] (Submitted)

Text FPSK2 2021 36.pdf Download (3MB)

Abstract

Escherichia coli, E. coli, is a rod-shaped Gram-negative bacterium that commonly inhabits the lower intestine of warm-blooded animals. Some E. coli strains are harmful which can cause food poisoning, meningitis, and other infections in humans. As the in vivo model of E. coli infection is lacking and modelling human diseases in animals is complicated, the non-mammalian model is an alternative to simulate human diseases due to its advantages such as reliability and convenience. Achroia grisella, a lesser wax worm, was proposed as an alternative model for studying bacterial diseases. The innate immune response of insects is very comparable to that of vertebrates, though they are lacking an adaptive immune response. Therefore, A. grisella larvae were employed in this study and have assessed the larvae as a potential animal model on the pathological changes at the morphological level. Objective: In this study, we aimed to observe the morphological changes in the A. grisella larvae upon E. coli infection. Methodology: The subcultured E. coli (ATCC 25922) in Luria Bertani (LB) were incubated at 3 different periods to obtain 3 different Optical Density (OD) values which were recorded at 600nm respectively. The cultures were washed twice with 1X Phosphate-Buffered Saline (PBS) by using the centrifugation method. The serial dilution was performed on the 96- wells plate and incubated overnight. Meanwhile, 10 μl of E. coli inoculum of different concentrations was placed onto the Nutrient Agar (NA) for the colony-forming unit (c.f.u) purposes and incubated overnight. Ten last instar stages of A. grisella larvae per group (4 weeks of age) were inoculated with 10 ul of E. coli inoculum each based on three different parameters and incubated at room temperature. The morphological changes were monitored within 5 days of post-infection on the larval activity, cocoon formation, melanization, and survival. Results: An inoculum of E. coli (P3: <1.0 x 108) at the OD value of 0.751 AU has shown the largest decrease in larval viability with a survival percentage of 20% followed by (P1: 3.6 x 107 and P2: 3.0 x 109 larvae-1) with 30% survival at the OD value of 0.167 and 0.406 AU respectively. There were distinctive black spots on the larvae and complete melanization, which led to death. Discussion: The larvae died due to bacterial infection based on the morphological changes when compared to control. The earliest decrease in larval survival is from the highest intensity of infection, from P3: <1.0 x 108, indeed, the rate of melanization is initially higher whereby two larvae have formed dark spots. This shows the immune response of larvae has evoked through melanization at which the deposited melanin in haemolymph surrounds the microbes and aids in pathogen killing. Conclusion: This study has proven that the A. grisella larvae can be used as a model as it has shown morphological changes due to infection, indeed, it can act as an alternative to experimental infection of rodents for pathogenicity evaluation of diseases.

Item Type:	Project Paper
Faculty:	Faculty of Medicine and Health Science
Depositing User:	Ms. Nor Safa'aton Saidin
Date Deposited:	22 Aug 2023 07:17
Last Modified:	22 Aug 2023 07:17
URI:	http://psaspb.upm.edu.my/id/eprint/1144

Actions (login required)

View Item