INVESTIGATION OF ACID RESISTANCE OF ESCHERICHIA COLI STRAINS
Food Science Research
2010 Annual Report
1a.Objectives (from AD-416)
The purpose of this study is to determine the survivability of Escherichia coli O157:H7 strains isolated from five sources (foods, bovine carcasses, bovine feces, water, and human) in acetic acid solutions under conditions that are typical of acidified foods.
1b.Approach (from AD-416)
The survivability of E. coli O157:H7 strains in acidified foods will be investigated under a variety of environmental conditions. Pure and mixed culture cell suspensions will be tested to determine acid resistance under various atmospheric conditions, pH values, and ionic strengths. The genetic relationships between strains will be characterized to determine if there are correlations between genotype and acid resistance phenotype. Genes relating to acid resistance may be identified.
This project supports Objective 1 of this in-house project: development of fundamental knowledge of the biochemistry of bacterial adaptation to acidified environments. In collaboration with scientists at Kangwon University, in Kangwon South Korea, the acid resistance of 50 pathogenic E. coli strains was investigated. Under this cooperative research agreement we have previously shipped 50 strains to Kangwon University. The survival of these strains in acid solutions typical of acidified vegetables was found to vary with the source of isolation of the bacterial strain. Research progress has been monitored by email and telephone conversations. Strains from food sources were found to be less acid resistant than strains isolated from cattle feces or meat. These unexpected results will be used to support further research to investigate how pathogenic E. coli strains survive in acid and acidified foods.