Abstract: 【Aim】 The microbiota of insect guts plays important roles in food digestion, development and environmental suitability. This study aims to study the composition and antibiotic susceptibility of bacteria in the gut of the diamondback moth (DBM), Plutella xylostella (L.). 【Methods】 Bacteria from feces of the 3rd instar larvae of P. xylostella were isolated and identified by 16S rDNA analysis, and the antibiotic susceptibilities of these bacteria were tested by KirbyBauer disk diffusion method. 【Results】 There were six bacterial species of five genera in the gut of the 3rd instar larvae of P. xylostella, including Enterococcus mundtii, two species of Erwinia, Pantoea agglomerans, Paenibacillus sp. and Pseudomonas oryzihabitans, which were different from those known in the midgut of P. xylostella. E. mundtii was the most dominated bacterium. E. mundtii, E. persicina  and P. agglomerans were all resistant to penicillin, ampicillin, medemycin, clarithromycin and jiemycin, while presented similar susceptibilities to fosfomycin, vancomycin, doxycycline and some other antibiotics. 【Conclusion】 The bacterial microflora carried by P. xylostella have the characteristics of diversity and these bacteria have natural resistance to some antibiotics. Our study provides bacterial materials and foundation for the further study on functional bacteria and bacterial microflora in the gut of larval P.xylostella.

Key words: Plutella xylostella, feces, bacteria, antibiotic susceptibility, 16S rDNA, gut