ABSTRACT
Objective To construct a mutant strain of Nocardia farcinica ( N. farcinica ) IFM10152 with mammalian cell entry 4A gene (mce4A) deletion and to analyze the function of that gene dur-ing infection. -ethods The mutant strain of N. farcinica was constructed through in-frame deletion without antibiotic labeling and verified by PCR and sequencing analysis. To analyze the function of mce4A gene in the interaction between N. farcinica and host cells, in vitro growth experiment, macrophage killing experi-ment using THP-1 ( a human leukemia mononuclear cell line) as the model and adhesion and invasion exper-iments using HeLa cells ( cervical cancer epithelial cells) were carried out. Results The mutant strain with mce4A gene deletion was successfully constructed and named △mce4A. No significant difference in growth rate was observed between the mutant and the wild-type strains. After knocking out the mce4A gene, the ability of N. farcinica to resist macrophage killing was obviously weakened as well as its ability to adhere and invade. Conclusions The mutant strain of N. farcinica with mce4A gene deletion was successfully construc-ted. The mce4A gene might play an important role in the adhesion and invasion of N. farcinica to host cells and its survival in macrophages.