The vast majority of E. coli strains that colonize plant matter such as leafy greens are non-pathogenic, according to new research from scientists at the UK-based Institute of Food Research.
In a paper published in Environmental Microbiology, lead researcher Sacha Lucchini, PhD, and colleagues at the IFR took what they say is the first comprehensive look at the differences between E. coli populations on crop plants and those in the mammalian gut. In more than 100 isolates from leafy vegetables grown in fields in England—mostly spinach and arugula (Eruca sativa)—the researchers found no shiga toxin-producing E. coli strains.
“Only a tiny minority had genes that are sometimes associated with virulence,” Dr. Lucchini said. But recent outbreaks have clearly shown that E. coli strains do colonize on produce.
One observation made by Dr. Lucchini’s team may help future efforts to prevent such colonization. They found that E. coli can more easily thrive in the mammalian gut than on a leaf surface, where it faces the dangers of drying out and fluctuating temperatures. The researchers noted that thriving E. coli populations from plants tended to form biofilms—complex structures of bacteria connected by a matrix of proteins and sugars. These biofilms are believed to protect the bacteria from drying and help them to adhere to a surface, Dr. Lucchini added.
“While it would be very difficult to develop a technique to prevent E. coli from sticking to a plant’s surface, we are now exploring whether or not the data we have generated on these strains will help us to identify a possible contamination source and allow us to prevent the bacteria from ending up on plants in the first place,” Dr. Lucchini added.