A recent study by Dr Yolanda Moreno and colleagues from Universitat Politècnica de València in Spain looking at organically grown vegetables showed that during growth, harvest, transportation, and further processing and handling, fresh produce can be contaminated with pathogens from human or animal sources, through contact with soil, irrigation water, air, rain, insects, and during industrial produce-washing.
“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 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. Moreover, the FLA species Vermamoeba vermiformis which commonly causes severe infections in humans was found in a fifth (19%) of vegetable samples; and Acanthamoeba castellanii, which can cause blindness and encephalitis were identified in almost two thirds (63%) of samples.”
This introduces the need to thoroughly was organic vegetables before consumption, however that process could lead to releasing Legionella bacteria as well as other opportunistic pathogens into the environment if not carried out safely. This means that commercial (and domestic) kitchens could be an unwitting source of illness and so should be risk assessed.
Dr. Moreno said “Contamination can arise as a consequence of treating soil with organic fertilisers such as manure and sewage sludge and from irrigation water. Leafy greens are particularly susceptible to faecal contamination due to their proximity to the ground and the likelihood of humans consuming them without cooking”
Whilst we are talking about eating your greens…
A study entitled “Tissue remodelling by an opportunistic pathogen triggers allergic inflammation” by Karen Agaronyan et al (DOI:https://doi.org/10.1016/j.immuni.2022.04.001). has shown that Pseudomonas aeruginosa can manipulate our immune system into producing mucus when it shouldn’t. They do this in our nose which can be a significant problem for patients with Cystic Fibrosis. The clever trick not only allows the microbe to avoid destruction but also gives it a rich source of fuel to keep growing.
Both Legionella and Pseudomonas aeruginosa are relatively common opportunistic pathogens in workplace environments which is why two British Standards exist to help risk assess their presence. These British Standards are BS8580 Part 1: 2019 “Water quality – Risk assessments for Legionella control – Code of practice” and BS 8580Part 2:2022 “Water quality. Part 2: Risk assessments for Pseudomonas aeruginosa and other waterborne pathogens— Code of practice”. These two documents provide detailed guidance on how to carry out risk assessments for opportunistic pathogens in engineered water systems
Collaton Consultancy Limited is a specialist water treatment consultancy offering training, expert witness, Legionella and Pseudomonas consultancy and Authorising Engineer (Water) services. If you require any help or advice contact us via general@collatonconsultancy.com
Legionella Risk Management 