Autoinducer-2 activity of gram-negative foodborne pathogenic bacteria and its influence on biofilm formation.
This study evaluated whether autoinducer-2 (AI-2) activity would be associated with biofilm formation by Salmonella and Escherichia coli O157:H7 strains on food contact surfaces. In study I, a Salmonella Typhimurium DT104 strain and an E. coli O157:H7 strain, both AI-2 positive, were individually inoculated into 50 mL of Luria-Bertani (LB) or LB + 0.5% glucose (LBG) broth, without or with stainless steel or polypropylene (Salmonella) coupons. At 0, 14 (Salmonella), 24, 48, and 72 h of storage (25 degrees C), cells in suspension and detached cells from the coupons, obtained by vortexing, were enumerated on tryptic soy agar. In study II, a Salmonella Thompson AI-2-positive strain and an AI-2-negative strain, and an E. coli O157:H7 AI-2-positive strain and an AI-2-negative strain were inoculated into LB broth with stainless steel coupons. Cells were enumerated as in study I. In both studies, AI-2 activity was determined in cell-free supernatants. Cell numbers of S. Typhimurium DT104 on biofilms were higher (P < 0.05) in LB than those in LBG, while the E. coli O157:H7 strain showed no difference (P>or= 0.05) in biofilm cell counts between LB and LBG after storage for 72 h. Both S. Typhimurium DT104 and E. coli O157:H7 strains produced higher (P < 0.05) AI-2 activity in LBG than LB cell suspensions. Cell counts of AI-2-positive and-negative S. Thompson and E. coli O157:H7 strains were not different (P>or= 0.05) within suspensions or coupons (study II). The results indicated that, under the conditions of this study, AI-2 activity of the pathogen strains tested may not have a major influence on biofilm formation on food contact surfaces, which was similar between AI-2-positive and -negative strains.
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Center for Meat Safety and Quality, Department of Animal Sciences, 1171 Campus Delivery, Colorado State University, Fort Collins, CO 80523, USA.
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D001422:Bacterial Adhesion; D018441:Biofilms / Q000254:growth & development*; D018533:Biomass; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D019453:Escherichia coli O157 / Q000472:pathogenicity / Q000502:physiology*; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods; D006714:Homoserine / Q000031:analogs & derivatives* / Q000378:metabolism; D007783:Lactones / Q000378:metabolism*; D011126:Polypropylenes; D012486:Salmonella typhimurium / Q000472:pathogenicity / Q000502:physiology*; D013193:Stainless Steel; D013997:Time Factors
D007783:Lactones; C091088:N-octanoylhomoserine lactone; D011126:Polypropylenes; D013193:Stainless Steel; D006714:Homoserine