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Title: Effect of curli expression and hydrophobicity of E. coli O157:H7 on attachment to fresh produce surfaces

Author
item Patel, Jitu
item Sharma, Manan
item RAVISHANKAR, SADHANA - University Of Arizona

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2010
Publication Date: 2/8/2011
Citation: Patel, J.R., Sharma, M., Ravishankar, S. 2011. Effect of curli expression and hydrophobicity of E. coli O157:H7 on attachment to fresh produce surfaces. Journal of Applied Microbiology. 110:737-745.

Interpretive Summary: Bacterial attachment to produce surface is the first step of contamination event. We evaluated the effect of curli expression and cell hydrophobicity on attachment of E. coli O157:H7 to intact and cut lettuce and cabbage surfaces. Curli expressing E. coli O157:H7 strains 4406 and 4407 were more hydrophobic and attached to intact and cut cabbage surfaces at higher numbers than that of other strains. Differences in E. coli O157:H7 populations attached to these produce surfaces were not significant (P > 0.05). All E. coli O157:H7 strains attached rapidly on intact and cut produce surfaces. E. coli O157:H7 attached preferentially to cut surface of all produce; however, the difference between E. coli O157:H7 populations attached to intact and cut surfaces was similar (P > 0.05) in most cases. E. coli O157:H7 attachment and attachment strength to intact and cut produce surfaces increased with time. Increased attachment of E. coli O157:H7 on cut surfaces necessitates effective produce wash to kill E. coli O157:H7 on produce. Understanding the attachment mechanisms of E. coli O157:H7 to produce surfaces will be helpful in developing new intervention strategies to prevent produce outbreaks.

Technical Abstract: Aim: To investigate the effect of curli expression on cell hydrophobicity, biofilm formation, and attachment to cut and intact fresh produce surfaces. Methods and Results: Five E. coli O157:H7 strains were evaluated for curli expression, hydrophobicity, biofilm formation, and attachment of E. coli O157:H7 strains to intact and cut fresh produce (cabbage, Iceberg lettuce and Romaine lettuce) leaves were determined. Biofilm formation was stronger when E. coli O157:H7 were grown in diluted TSB (1:10). Curli expressing E. coli O157:H7 strains 4406 and 4407 were more hydrophobic and attached to intact and cut cabbage surfaces at higher numbers than that of other strains. Differences in E. coli O157:H7 populations attached to these produce surfaces were not significant (P > 0.05). All E. coli O157:H7 strains attached rapidly on intact and cut produce surfaces. E. coli O157:H7 attached preferentially to cut surface of all produce; however, the difference between E. coli O157:H7 populations attached to intact and cut surfaces was similar (P > 0.05) in most cases. E. coli O157:H7 attachment and attachment strength (SR) to intact and cut produce surfaces increased with time. Conclusions: Curli producing E. coli O157:H7 strains attaches at higher numbers on produce surfaces. Increased attachment of E. coli O157:H7 on cut surfaces necessitates effective produce wash to kill E. coli O157:H7 on produce. Significance and Impact of the Study: Understanding the attachment mechanisms of E. coli O157:H7 to produce surfaces will be helpful in developing new intervention strategies to prevent produce outbreaks.