Isolation and identification of bacterial pathogens causing infections in Bombyx mori

The present study was planned to assess the influence of Morus alba, Morus nigra and mixed mulberry leaves diet on the health and disease susceptibility to Bombyx mori. 5g of dried leaves samples of Morus alba, Morus nigra and mixed mulberry leaves were used to done proximate analysis. The silkworms were reared for 32 days under semi-controlled conditions, with an optimum temperature of 25-28°C and humidity maintained at 70-80% throughout the experimental period. Diseased silkworms showing clinical signs such as dark brown bodies, slow growth, secretions from the body, slow movement, and shrinkages of the body were collected from the experimental site and were used for bacterial enumeration and isolation. The bacteria were isolated from the gut, whole body, and outer body surface. The isolation of bacteria from diseased silkworms revealed 157 distinct colonies from different sources. The highest number of colonies was observed in samples taken from the gut (62 colonies), followed by the whole body (53 colonies) and the outer body surface (42 colonies). The Pearson’s correlation analysis (Pearson’s r = 0.87, p < 0.001) revealed a strong association between the severity of disease symptoms and bacterial load, especially in the gut-derived samples. Preliminary identification based on colony morphology, growth characteristics, and simple biochemical tests suggested the presence of potential bacterial pathogens such as Staphylococcus spp., and Escherichia coli. It is suggested that adopting mixed mulberry leaves diets and enhancing sanitary measures can improve overall health and productivity in sericulture.