The research team also analyzed samples from a similar lethal case of a 31-year-old man in 2002 with so much skin damage that he was first admitted to a hospital burn unit.
Telltale fingerprint points to new species
Han and M. D. Anderson colleagues diagnose infections in cancer patients. Han developed in 2002 a way to identify unusual bacteria by analyzing small but significant differences in the 16S ribosomal RNA gene. "This is like a fingerprint analysis to solve crimes," Han said. He has discovered and named several new bacterial species that cause unusual infections.
Across a group of bacteria called mycobacteria, the 16S rRNA gene is 93 to 100 percent identical. There are 110 species of mycobacteria, with those causing tuberculosis and leprosy the best known. Sequencing the 16S rRNA gene is a fast and accurate way to identify mycobacteria, which usually grow slowly, Han noted. Accurate identification improves patient care decisions.
Han and colleagues compared the lethal bacterium's 16S rRNA gene and five other genes to other mycobacteria. They found that the bacterium had the most in common with Mycobacterium leprae, previously thought to be the sole cause of leprosy.
Yet there were also significant differences with M. leprae. The lethal bacterium's 16S rRNA gene sequence differed by 2.1 percent. "That may sound like a small difference, but to anyone familiar with mycobacteria, it's huge," Han said. In all previously studied M. leprae strains, no variation in the 16S rRNA gene had been noted at all.
Analysis of the other five genes turned up more differences. The researchers named the new species Mycobacterium lepromatosis. They have since confirmed M. lepromatosis as the cause of two lethal cases of DLL in Singapore.
What's next for M. lepromatosis
The team is working to better
|Contact: Scott Merville|
University of Texas M. D. Anderson Cancer Center