Via LiveScience.com: Super Salmonella Bacteria Found. Excerpt:
Certain Salmonella bacteria, the microbes that cause food poisoning, have the potential to become as much as 100 times more virulent than normal, recent research has found.
In the study, these super-bugs overcame the protective effects of a Salmonella vaccine, killing vaccinated mice.
The scientists found that some of the bacteria have the potential to become much nastier than others, a result that has implications for averting outbreaks among humans and animals, they write in a study published April 12 in the journal PLoS Pathogens.
Led by Douglas Heithoff of the University of California, Santa Barbara, they used a technique called animal passage, in which a pathogen is weakened or strengthened by infecting an animal with it. In recent research that created a more transmissible version of the H5N1 flu virus, scientists passed it between ferrets. In this case, the scientists created more virulent forms of the bacteria by infecting mice.
They found that certain strains had the potential to become hyperinfectious and were among the most virulent Salmonella ever reported, they write.
To measure the nastiness of the strain, the team looked at how much was required to kill half of the infected animals. The hypervirulent strains required a dose as little as 100-fold lower than normal to be that lethal.