Control of foodborne pathogens on fresh-cut fruit by a novel strain of Pseudomonas graminis

Abstract

The consumption of fresh-cut fruit has substantially risen over the last few years, leading to an increase in the number of outbreaks associated with fruit. Moreover, consumers are currently demanding wholesome, fresh-like, safe foods without added chemicals. As a response, the aim of this study was to determine if the naturally occurring microorganisms on fruit are “competitive with” or “antagonistic to” potentially encountered pathogens. Of the 97 and 107 isolates tested by co-inoculation with Escherichia coli O157:H7, Salmonella and Listeria innocua on fresh-cut apple and peach, respectively, and stored at 20 °C, seven showed a strong antagonistic capacity (more than 1-log unit reduction). One of the isolates, CPA-7, achieved the best reduction values (from 2.8 to 5.9-log units) and was the only isolate able to inhibit E. coli O157:H7 at refrigeration temperatures on both fruits. Therefore, CPA-7 was selected for further assays. Dose-response assays showed that CPA-7 should be present in at least the same amount as the pathogen to adequately reduce the numbers of the pathogen. From the results obtained in in vitro assays, competition seemed to be CPA-7's mode of action against E. coli O157:H7. The CPA-7 strain was identified as Pseudomonas graminis. Thus, the results support the potential use of CPA-7 as a bioprotective agent against foodborne pathogens in minimally processed fruit.

The authors are grateful to the ISAFRUIT Project, which was funded by the European Commission under the thematic priority 5-Food Quality and Safety of the 6th Framework programme of RTD (Contract n°. FP6-FOOD-CT-2006-016279), and to the Spanish Government for research project (AGL-2004-06027, INIA researcher contract, Orden CTE/3597/2003, BOE 23/12/2003) and for grant AP2006-03711. Disclaimer: The views and opinions expressed in this publication are purely those of the writers and may not in any circumstances be regarded to state the official position of the European Commission.