Organic vegetables are often contaminated with harmful bacteria that cause disease, a new study warns. According to scientists, people who buy products that have been treated with organic fertilizers such as manure may regret their choice.
More than 50 species of potentially harmful bacteria have been found on samples of organic spinach and lettuce. Organic fruits and vegetables are becoming increasingly popular as more people eat healthy diets and avoid pesticides, fertilizers and herbicides.
But now scientists in Spain have discovered that they could be contaminated with harmful bacteria of human or animal origin. These are likely transferred to vegetables during growing, harvesting, transportation, processing and handling.
Vegetables in particular can contain single-celled organisms like free-living amoebas (FLA), which feed on bacteria, some of which can be extremely harmful to humans. These nasty bacteria, nicknamed Trojan horses, resist the body’s digestion and pose a serious threat to anyone who eats them.
Dr Yolanda Moreno from the Universitat Politècnica de València said: “Food and food-related environments create an ideal meeting place for free-living amoebas and pathogenic bacteria. vegetables and their role in the transmission of human pathogens.
Lettuce and spinach samples were taken from local supermarkets in Valencia between November 2020 and May 2021. A special scientific technique was then used to identify the DNA of any bacteria found inside the amoebas.
The main types of bacteria identified were Flavobacterium and Pseudomonas, which do not usually cause disease in humans. But 52 types of harmful bacteria, including Legionella, Salmonella and Arcobacter, were found in a third of the samples.
These can cause serious illnesses like pneumonia and gastrointestinal illnesses. Another species called Vermamoeba vermiformis which often causes serious infections was found in one fifth of the vegetable samples. Acanthamoeba castellanii, a bacterium capable of causing blindness and encephalitis, was also recorded in nearly two-thirds of the samples – 63%.
Dr Moreno said: “The presence of bacteria of public health concern contained inside free-living amoebae suggests that they are vehicles that can readily transmit pathogens capable of reaching humans and causing health problems. health through contaminated organic vegetables. Contamination can occur as a result of treating the soil with organic fertilizers such as manure and sewage sludge and irrigation water.”
Larger studies are needed in different countries to better understand the quality and safety of organic vegetables. Dr Moreno said: “Leafy greens are particularly susceptible to fecal contamination due to their proximity to soil and the likelihood of humans consuming them uncooked. Our findings also underscore the need to educate the public on the safe and proper handling of fresh organic vegetables before eating them fresh or lightly cooked.
The results were to be presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Lisbon, Portugal.
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