Whole-genome sequencing of rough <i>Brucella melitensis</i> in China provides insights into its genetic features

<i>Brucella</i> spp. can cause the zoonosis brucellosis, which affects public health and safety and even economic development. <i>B. melitensis</i> has a smooth phenotype, while 28 <i>B. melitensis</i> isolates had a rough phenotype in 2018. In this study, rough phenotype detection and whole genome sequencing methods were used to analyze the genetic features of rough <i>B. melitensis</i>. A drug susceptibility test was also performed. The results showed that the rough <i>B. melitensis</i> strains originated from strains isolated in China rather than from foreign strains. Furthermore, an MS tree showed that 9 complexes to be epidemic in China. For the rough <i>B. melitensis</i> strains, expression of the metabolic function genes varied in the earlier stages of evolution compared to the cellular process and signalling function genes. Expression of some transcriptional regulatory factors also varied in the later stages of evolution, and compared to MFS transporter genes, ABC transporter genes varied in the earlier stages. Moreover, as there was no significant difference in rifampicin, doxycycline and streptomycin susceptibility between the smooth and rough <i>B. melitensis</i> strains, treatment of brucellosis was not affected by strain type. This study provided important information for understanding the genetics and evolution of rough <i>B. melitensis</i> in China.