Study of Arcobacter spp. contamination in fresh lettuces detected by different cultural and molecular methods

Arcobacters are considered potential emerging food and waterborne pathogens. However, there is no data on the presence of Arcobacter spp. in fresh vegetables. Therefore the objective of this research was to study the presence of Arcobacter spp. in fresh lettuces.Fifty fresh lettuces purchased from different local shops in Valencia (Spain) were analyzed. The assay was performed simultaneously by cultural and molecular methods. Isolates were identified by real-time, multiplex PCR and restriction fragment length polymorphism analysis of PCR-amplified DNA fragment (PCR-RFLP). Finally, all the isolates were genotyped using the randomly amplified polymorphic DNA (RAPD-PCR) method.Arcobacter sp. was detected in 10 of the 50 samples (20%) by real-time PCR, being A. butzleri the unique detected species by mPCR. The detection levels obtained by conventional PCR (7 samples/50, 14%) were slightly lower. These seven samples were found to be positive also by culture isolation. All 19 obtained isolates were identified as A. butzleri by multiplex PCR and PCR-RFLP. Great genetic heterogeneity among the isolates was observed by RAPD-PCR profiling.To our knowledge, this is the first study in which Arcobacter spp. is detected in fresh vegetables such as lettuces. Although these foods are generally considered safe, given the large quantities consumed and the fact that further cooking is absent, lettuce could be a source of Arcobacters of public health concern.

Research highlights
► First study in which Arcobacter spp. is detected in fresh vegetables such as lettuces.
► All the Arcobacter-positive lettuces had been purchased from the same retail shop.
► Arcobacter sp. was detected in 10 of the 50 samples (20%) by real-time PCR. A. butzleri was the only detected species in all of the 10 PCR-positive samples.
► Seven samples were found to be positive by culture. A total of 19 isolates were obtained from these samples, and all of them were identified as A. butzleri.
► A total of 9 different RAPD-PCR profiles could be distinguished among the 19 A. butzleri isolates. DNA patterns of the isolates showed a substantial intra-species genetic heterogeneity.