Journal Club - Organic Vegetables are Contaminated with Microbes

People are consuming organic vegetables not only because organic production help reduce public health risks, but mounting evidence shows that food grown organically are rich in nutrients,  such as Vitamin C, iron, magnesium, and phosphorus, with less exposure to nitrates and pesticide residues in organically grown fruits, vegetable.     

HOWEVER New research presented at this year's European Congress of Clinical Microbiology & Infectious Diseases in Lisbon, Portugal suggests that disease-causing amoebas that live on 1,10 organic leafy vegetables can shelter human pathogens like Pseudomonas, Salmonella, and  Helicobacter and are a potential risk to public health. The study is by Dr Yolanda Moreno FROM SPAIN.

There is a growing demand for organically grown fruit and vegetables as people strive to eat healthy diets and amid concerns over potential contamination from pesticides, chemical fertilisers and herbicides.

Foodborne illness from consuming contaminated fresh produce is common and can have serious effects on human health, especially when eaten raw. Vegetables can become contaminated with certain protozoa (single-celled organisms) such as free-living amoebae (FLA), that  feed on bacteria and can act as hosts to pathogenic bacteria (the so-called "Trojan horses") which resist FLA digestion and could be a threat to public health.

To conduct a preliminary study of the FLA microbiome isolated from organic vegetables, Researchers collected 17 samples of lettuce and spinach between November 2020 and May 2021.

To investigate the degree of contamination, researchers used a  metagenomic technique that identifies DNA in all bacteria present inside FLA. The results were assessed to determine what kinds of microbes (Microbiome) were in each sample.

The main bacterial types identified were with Flavobacterium (found in 10% of vegetable samples) and Pseudomonas (10%) , many of which do not cause disease in humans. However, a third of samples (34%) contained 52 potentially disease-causing types of bacteria including  Legionella, Salmonella, and Arcobacter. The resulting infections can cause illnesses—including pneumonia and gastrointestinal illness.

Dr. Moreno Said "The presence of bacteria of public health concern contained inside the free- living amoebae suggests that they are vehicles that can easily transmit pathogens capable of reaching humans and causing health problems through contaminated organic vegetables". "Contamination can arise as a consequence of treating the soil with organic fertilizers such as manure and sewage sludge and from irrigation water. Our results also stress the need to educate the public on safe and proper handling of fresh organic vegetables before eating them fresh or slightly cooked."