Title: Efficacy of Pseudomonas fluorescens for biocontrol of Escherichia coli 0157:H7 on spinach Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 17, 2013
Publication Date: July 28, 2013
Citation: Olanya, O.M., Ukuku, D.O., Niemira, B.A., Annous, B.A., Sommers, C.H. 2013. Efficacy of Pseudomonas fluorescens for biocontrol of Escherichia coli 0157:H7 on spinach. Meeting Abstract. Journal of Food Protection, Volume 76 (supplement),Page 35. Technical Abstract: Control of foodborne pathogens on leafy green vegetables is crucial for consumer food safety. Biocontrol microbes may suppress foodborne pathogen growth and enhance existing post-harvest intervention controls. The efficacy of Pseudomonas fluorescens for biocontrol of Escherichia coli O157:H7 was determined on baby spinach. P. fluorescens strains 2-79, Q2-87, and Q8R-1 (non-pectolytic and non-plant pathogenic) were applied on spinach using the dip inoculation method, prior to inoculation with E. coli O157:H7 strains 43894, 43895, and 35150 individually or in a cocktail mixture. The inoculated spinach was stored at 20 deg C for 24 and 48 hours, and then evaluated for E. coli O157:H7 populations using Restaino and Frampton E. coli O157:H7 chromogenic medium. In subsequent experiments, the effects of storage time (24 and 48 hrs) and temperatures (5, 10, 15, 20, 25, and 30 deg C) on the efficacy of biocontrol were determined. The reduction of E. coli O157:H7 by P. fluorescens was computed relative to the control. The mean reduction of E.coli O157:H7 by P. fluorescens ranged from 0.5-2.1 log CFU/g of spinach. The efficacy of biocontrol was significantly (P<0.05) affected by storage temperature as suppressive effects were greater at 15 deg C (1.5-2.4 log CFU/g) than at other temperatures (<0.93 log CFU/g). As expected, the reduction of E. coli O157:H7 populations varied between storage times of 24 and 48 hrs. These results imply that P. fluorescens may provide low to moderate reductions of E. coli O157:H7 populations on spinach. Biocontrol strategy may be improved by combining it with other post-harvest intervention measures.