Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the primary vector of Candidatus Liberibacter asiaticus (Las), which causes the devastating disease Huanglongbing (HLB) in Asian citrus. To examine the effects of pathogens on the diversity and structure of insect-associated bacterial communities, we carried out a molecular analysis using healthy D.citri and Las-infected D.citri as a vector-pathogen model. 16S rRNA Illumina sequencing analysis of D.citri revealed shifts in its microbial diversity in response to pathogen infection. The phylum Proteobacteria predominated in D.citri representing 89.40 and 91.73% of the bacterial communities, while remaining bacterial sequences were mainly assigned to the phyla Actinobacteria, Firmicutes, Bacteroidetes and Acidobacteria. The relative proportions of different groups of bacteria changed significantly after pathogen infection. The relative abundance of bacterial communities between healthy D.citri and Las-infected D.citri were different, and the relative abundance of most dominant bacteria decreased, such as Oscillospira, Lactobacillus and Rubrobacter. However, the relative abundance of Wolbachia increased from 1.81 to 2.14%, and there was no difference in the abundance of Carsonella. In pairwise comparisons, the clone library from healthy D.citri contained greater 16S rRNA gene diversity, as reflected by the higher Shannon index at 2.937 versus 2.756 for the healthy and Las-infected clone libraries, respectively. These data indicated that Las infection has a profound effect on the structure and composition of the bacterial community associated with D.citri.