Detection of Helicobacter pylori in vegetables (Lettuces Salads).
l. Bayas Morrejon; A. Gonzalez Pellicer; L. Moreno Mesonero; Y. Moreno Trigos; M. A. Ferrus Perez
Universitat Politecnica de Valencia, Valencia, Spain
Helicobacter pylori has been classihed as a Class 1 carcinogen by W.H.O. Although H. pylori is a major waterborne pathogen, its occurrence in vegetables is unknown. Therefore, the goal of this work was to study its presence in fresh vegetables.
One hundred vegetables samples (21 spinach, 34 chards, 41 lettuces and 4 cabbages) were analyzed by conventional PCR, using specific primers to amplify a 394-bp fragment from vacA gene of H. pylori. Presumptive PCR positive samples were also studied by real-time PCR using the same primers. To confirm the identification, amplicons were run in a gel and the specific bands were excised, purified and sequenced. The homology of the sequence with the corresponding H. pylori vacA gene fragment was determined by a BLAST alighment.
By conventional PCR, in 5 of the 100 samples the specific 394-bp band was obtained, but with a dim staining. Results of real-time PCR of these five samples showed the expected Tm values (85.52-83.98)of the amplicon. However, only in one lettuce sample the amplified fragment showed the specific H. pylori expected sequence. By BLAST alignment, the sample was 99-100% similar to the H. pylori vacA gene sequence obtained from GenBank. It is the first time that H. pylori has been detected in a vegetable sample in Spain.
Although more studies are necessary, lettuces could play an important role in Helicobacter transmission to humans, because they are usually consumed without cooking and they are the vegetable-type most consumed in salads.