New research sheds light on how the bacteria behind typhoid fever can hide in the body and may help explain how "Typhoid Mary" remained asymptomatic while infecting dozens of New Yorkers in the 1900s.
Mary Mallon was the world's most famous asymptomatic carrier of typhoid fever. She was arrested in the early 1900s after health inspectors realized she had worked as a cook in several contaminated houses from 1900 to 1907.
Investigators at the time discovered through urine and bowel samples that Mallon was shedding large amounts of the bacteria, even though she remained healthy. Although Mallon pledged to stop working as a cook, she was later caught preparing food in a hospital with a typhoid fever outbreak and ultimately sent to live out her life in a hospital bungalow on North Brother Island.
Salmonella typhi—the bacteria that causes typhoid fever—has long been known to infect the gallbladder. In a study published this month in Cell Host & Microbe, Stanford University and UC-San Francisco researchers explained how the bacteria also can "hack" into macrophages, the immune system "attack cells" that usually consume invading bacteria.
In experiments with mice, they found that S. typhi use the genetic programming of macrophages generally associated with the later stages of infection to trigger the production of glucose, which it then feeds off of (McNeil, New York Times, 8/26; Mohan, "Science Now," Los Angeles Times, 8/14).