Psk-1 virulence gene-induced pulmonary and systemic tuberculosis in a young female with normal immune function

Abstract

Background Tuberculosis is a chronic infectious disease and an important public health threat. Despite China’s achievements in controlling tuberculosis, the prevalence of this disease is still very high, with 895,000 new cases annually. This case report aimed to ascertain why a Mycobacterium tuberculosis strain caused such a severe infection in a young adult with normal immune function. Case presentation: We present the case of a young female with normal immune function without the history of receiving bacillus Calmette–Guérin vaccine, who suffered from severe pulmonary tuberculosis and secondary systemic disseminated tuberculosis. The M. tuberculosis was isolated from the bronchoalveolar lavage fluid of the patient. Further, we analysed the whole-genome sequence of the strain and designated it BLM-A21. Additional M. tuberculosis genomes were selected from the Virulence Factor Database (http://www.mgc.ac.cn/cgi-bin/VFs/genus.cgi?Genus=Mycobacterium), developed by the bioinformatics research team of the Institute of Pathogenic Biology, Chinese Academy of Medical Science. The evolutionary tree of disseminated tuberculosis was then built using the PhyML maximum likelihood software. Further gene analysis revealed that BLM-A21 has similar virulence genes to the strains CDC 1551 and H37Rv, which have lower dissemination, except for the pks-1 gene, which may be the key virulence gene responsible for the high dissemination ability of this M. tuberculosis strain. Conclusions We speculated that the pks-1 virulence gene of this strain induced severe pulmonary tuberculosis and secondary systemic disseminated tuberculosis in this adult female with normal immune function.