The new bacterium was identified in a patient with chronic granulomatous disease (CGD), a rare genetic disorder that impairs the immune system. In the patient, the bacterium caused fever, lymph node inflammation, and weight loss, but not death.
The journal also published an editorial entitled, "Extending the Spectrum of Human Pathogens," which comments on the significance of the discovery.
Usually, our immune systems fight off most bacteria and fungi with everyday ease, thwarting infection. But patients with CGD cannot control attacks by certain bacteria and fungi. The disorder prevents immune cells called neutrophils from functioning properly, and recurrent --and potentially life-threatening-- infections result.
The team isolated the new bacterium from the patient's swollen lymph nodes and demonstrated its pathogenesis. "Our first concern was to determine whether this organism was truly associated with his clinical syndrome," the team wrote.
Despite ineffective neutrophil immune cells, the patient's immune system still tagged the bacterium as an invader. Researchers also exposed CGD mice to the bacterium, recreating the appearance of the patient's infection. Researchers were then able to retrieve the bacteria from the mice's spleens, which are disease-fighting organs. These factors all support the pathogenic nature of the bacterium.
Because the bacterium does not cause death, it may be provide useful comparison with more menacing bacteria and fungi in CGD patients. "Given its apparent low virulence, further investigation of this organism may shed light on the mechanisms of microbial killing in CGD. Comparing the genome of this organism to other 13 available genomes of CGD pathogens may provide clues to virulence properties that they share in common," according to the article.
The research team, composed of scientists from the National Institutes of Health and Rush Medical College, have proposed Granulobacter bethesdensis as the bacterium's name.