Study on E. coli and Salmonella biofilms from fresh fruits and vegetables

Abstract

Foodborne outbreaks associated with fresh fruits and vegetables are on the rise worldwide. Biofilm formation is one of the important traits of pathogens making them strongly attached to substrates as well as express virulence phenotypes. Present study investigates the biofilm forming ability of E. coli and Salmonella sp. isolated from fresh fruits and vegetables. A total of 53 strains, including 35 E. coli and 18 Salmonella sp. isolated from different fruit and vegetable samples were taken into account for the study. Initial screening for biofilm formation was done using Congo Red agar plate test. Results revealed that 22.8% E. coli and 22.2% Salmonella sp. were potential biofilm formers. However, the MTP (Micro-Titre Plate) assay suggested more isolates of both E. coli and Salmonella sp. were moderate to strong biofilm producers. Agar plate diffusion assay with Agrobacterium tumefaciens NTL-4 showed the production of quorum signaling molecules (AHLs) by three isolates of E. coli and one Salmonella sp. Two E. coli isolates showed a significant amount of EPS production indicating higher biofilm forming potential. The Presence of LUX R homologue gene (sdiA) in two of the Salmonella isolates were confirmed by PCR which demonstrated their potential pathogenicity. Results of the work underline the biofilm forming and potentially virulent capacities of isolates from the surface of fruits and vegetables.

Genotypic and phenotypic characteristics associated with biofilm formation in Escherichia coli and Salmonella spp. isolated from ulam in Terengganu

“…While 2 (8.7%) E. coli isolates were recognized as saw morphotypes and did not produce biofilm. The current results were in accordance to previous authors that described the correlation between a phenotypic appearance on congo red agar and biofilm formation (Bokranz et al, 2005;Milanov, Prunic, Velhner, Todorovic et al, 2015;Amrutha et al,2017). Bokranz et al (2005) demonstrated that E. coli strains expressing rdar morphotype showed a higher capacity to form biofilms than saw strains.…”

Biofilm Formation by Multidrug-Resistant Serotypes of Salmonella Isolated from Fresh Products: Effects of Nutritional and Environmental Conditions

“…isolated from humans, animals, or food [5,33]. Amrutha et al [36] reported that 50% of Salmonella spp. isolated from different fruits and vegetables were strong biofilm producers/ while the rest were found to be moderate or weak biofilm producers.…”

Conventional and non-conventional disinfection methods to prevent microbial contamination in minimally processed fruits and vegetables

“…Biofilm formation starts with the microbial adhesion to the plant, being accessible for the bacteria that have flagella, allowing chemotaxis and swimming motility for colonization through surface adhesion ( McLandsborough et al, 2006 ). Researchers have demonstrated that Bacillus, Salmonella, Listeria, Staphylococcus, and Escherichia presented in FV are capable of biofilm formation, which is crucial for the virulence of the pathogenic strains ( Amrutha et al, 2017 ). Recently, Sun, Ye, et al (2021) demonstrated that E. coli O157:H7 formed a denser biofilm on cucumber tissues, especially in the vascular tissues.…”