Isolation and characterization of bacteria associated with silkworm gut under antibiotic-treated larval feeding

Abstract

The impact of antibiotics on growth, cocoon production was assessed in addition to isolation and characterization of bacteria associated with silkworm gut of infected larvae. Larval rearing was maintained at recommended conditions of temperature and humidity. Silkworm larvae showing abnormal symptoms were collected from the control group and dissected for gut collection. Bacteria were isolated from the gut content by spreading on agar plates and incubated at 37 °C for 48 hrs. Bacterial identification and phylogenetic analysis were carried out by 16S rRNA gene sequencing. The isolated bacteria were subjected to antimicrobial susceptibility test (disc diffusion methods) by using Penicillin (10 µg/mL), Tetracycline (30 µg/mL), Amoxicillin (25 µg/mL), Ampicillin (10 µg/mL), and Erythromycin (15 µg/mL). All isolated strains showed positive results for the catalase test. We isolated and identified bacterial strains (n = 06) from the gut of healthy and diseased silkworm larvae. Based on the 16S rRNA gene sequence, isolated bacteria showed close relation with Serratia, Bacillus, and Pseudomonas spp. Notably, 83.3% of strains were resistant to Penicillin, Tetracycline, Amoxicillin, Ampicillin, and Erythromycin but 16.6% showed antibiotic susceptibility to the above-mentioned commonly used antibiotics. Silkworm larvae fed on penicillin-treated leaves showed significant improvement in larval weight, larval length, and cocoon production. Significantly higher larval weight (6.88g), larval length (5.84cm), and cocoon weight (1.33g) were recorded for larvae fed on leaves treated with penicillin as compared to other antibiotics. Isolated bacterial strains showed close relation with Serratia spp., Bacillus spp. and Pseudomonas spp.

Evaluation of chitosan and silver nanoparticles Against isolated pathogens from Mulberry Silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) under laboratory conditions

“…Grasseriе (Viral disеase), Muscardine (Fungal disеase), Pеbrine (Micrоsporidian infеction) and Flachеrie, a syndromе inflеctеd by non-occluded virusеs, bactеrial and both in cоmbination are the frequеntly encountеred disеases to silkworm (Tao et al, 2011). Further, bactеrial septicеmia is оne of the most frequent silkworm disеases, which is usually caused by diffеrent types of pathogеnic bactеrium, including Bacillus, Pseudоmonas, Streptococcus and Staphylоcoccus (Jin and Lu, 2001;Tayal and Chauhan, 2017;Javaid et al, 2021).…”