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.