Preliminary study finds organic vegetables contaminated with widespread pathogenic microorganisms

New research to be presented at this year's European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Lisbon, Portugal (April 23), shows that the pathogenic amoeba that lives in organic vegetables can shelter human pathogens such as Pseudomonas, Salmonella, Helicobacter pylori and a potential risk to public health

Foodborne illnesses from consuming contaminated fresh produce are common and can have serious implications for human health, especially when eaten raw

Vegetables can be contaminated with certain protozoa (single-celled organisms), such as free-living amoeba (FLA), which feed on bacteria and can act as a source of pathogenic bacteria (so-called "Trojan horses") that resist FLA digestion.

"Food and the food-related environment create the ideal meeting place for free-living amoeba and pathogenic bacteria," explained Dr.

To conduct a preliminary study of the FLA microbiota isolated from organic vegetables, the researchers collected 17 lettuce and spinach samples from a local supermarket in Valencia between November 2020 and May 2021

To investigate the extent of contamination, the researchers used a metagenomic technique to identify the DNA of all bacteria within the FLA

The main bacterial types identified were Flavobacterium (found in 10% of vegetable samples) and Pseudomonas (10%), many of which do not cause disease in humans

In addition, the FLA species Vermamoeba vermiformis, which typically causes severe human infection, was found in one-fifth (19%) of vegetable samples; blindness and encephalitis were found in nearly two-thirds (63%) of samples.

Dr Moreno said: "Free-living amoeba harbors bacteria of concern to public health, suggesting that they are easily vectors of pathogens that can reach humans and cause health problems through contaminated organic vegetables.

Despite these important findings, the authors note that this study included only a small sample of leafy organic vegetables from one Spanish city, and larger studies from different countries are needed to learn more about the microbial quality and safety of organic vegetables