Molecular Characterization and Biofilm Formation of Escherichia coli from Vegetables

Abstract

Escherichia coli can cause diarrheal and extraintestinal illnesses in humans. Diarrheagenic E. coli can be transmit to human through consumption of contaminated food, including vegetables. Biofilm produced by E. coli during food processing plays a role in development of foodborne illnesses. Vegetables have often been involved in diarrheal E. coli infections. A total of 40 E. coli isolates from vegetables were tested to determine biofilm formation at 12°C, 25°C and 37°C by the crystal violet and MTT assays. All isolates were performed for the production of curli fimbriae and cellulose associated with biofilm formation on Congo red agar. Biofilm formation at 37°C, 25°C and 12°C was detected in 87.5%, 70% and 70% of the isolates, respectively. Biofilm formation among the E. coli isolates using the crystal violet and MTT assays showed a statistically significant difference between 12°C and 25°C as well as 12°C and 37°C (p < 0.05). However, no significant difference between 25 and 37°C (p > 0.05) was obtained. Three different morhotypes (bdar, pdar and saw) were identified based on the expression of curli fimbriae and cellulose. The incidence of the bdar morhotype was 27.5% and 50% at 25°C and 37°C, respectively. Prevalence of the pdar morphotype was 50% and 70% at 25°C and 37°C, respectively. At 25°C, only one isolate (2.5%) showed the saw morphotype. All isolates tested expressed curli fimbriae or cellulose, only three of which were non-biofilm producer using the crystal violet assay. This study demonstrated that the presence of biofilm forming E.coli isolates in vegetables may cause a risk to human health and food safety.