Deletion of licD2 gene leads to reduced virulence of Streptococcus pneumoniae

    LAN Kai, SHAN Youª²Lan, YUAN Jun, MENG Jiangª²Ping, ZHANG Xueª²Mei, YIN Yiª²Bing

    Department of Laboratory Medicine, Chongqing University of Medical Sciences, Chongqing 400016, China

    ¡¾Abstract¡¿AIM: To assess the role of licD2 gene in the virulence of Streptococcus pneumoniae. METHODS: licD2ª²deficient strain was constructed and identified by PCR. Relative quantitative RTª²PCR was applied to measure the expression levels of virulent factors and the virulence was studied by mice survival test. RESULTS: The expression of virulent factors in licD2ª²deficient strain was lower than that of wideª²type strain (P<0.05). The transformation capability of licD2ª²deficient decreased obviously, even completely lost. Mice virulence experiments showed that the survival time of wideª²type strain was less than 1 d, while that of licD2 mutation was more than 2 weeks (P<0.001). The elimination speed of licD2 mutation in mice blood was faster than that of the wideª²type. CONCLUSION: The deficiency of licD2 gene leads to decreased transformation capability and the expression of virulent genes, thus markedly reducing the bacterial virulence. ......