Roni Dengler in Discover:
In 1984, bacteria started showing up in patients’ blood at the University of Wisconsin Hospital and Clinic. Bacteria do not belong in the blood and such infections can quickly escalate into septic shock, a life threatening condition. Ultimately, blood samples revealed the culprit: A microbe that normally lives in the gut called Enterococcus faecalis had somehow infiltrated the patients’ bloodstreams. Doctors typically treat infections with antibiotics, but these bugs proved resistant to the drugs. The outbreak in the Wisconsin hospital lasted for four years.
Now researchers have finally figured out how this friendly gut bacteria morphed into a vicious pathogen in the blood. The discovery shows not only how the bacteria evolved new ways to survive in an environment entirely different from the gut, but it also shows how E. faecalis skirted both antibiotics and the immune system and sparked the outbreak.
More here.