Assessments of Plant and Microbial Interactions of Escherichia coli 0157:H7 and Salmonella on Romaine Lettuce and Development of Molecular Tools for Detection and Source Matching of Pathogenic and Commensal Escherichia coli Applied to Regional Investigations Relevant to Sources of Lettuce Outbreaks.
Wendy Anne Maduff
Thesis, Doctor of Philosophy (Food Science and Technology), University of California. 152 pages. 2008.
2008
บทคัดย่อ
Growth kinetics and adherence dynamics of Escherichia coli 0157:H7 isolates and Salmonella serotypes were compared on Romaine lettuce leaves which were inoculated with S. Michigan, S. Agona, S. Montevideo, or one of three E. coli 0157:H7 isolates and were recovered over 72 hours. The results show a significant increase (p<0.05) in recovered colony forming units (CFU)/Ieaf over 72 hours from the primary and secondary washes for all bacteria inoculated on greenhouse- and field-grown Romaine lettuce.
The influence of biosurfactant-producing Pseudomonas fluorescens on growth kinetics and adherence dynamics of E. coli 0157:H7 on greenhouse grown Romaine lettuce was investigated. The effect of biosurfactant secreted by P. fluorescens 123 (biosurfactant+) or the presence of P. fluorescens EG3 (biosurfactanC) on the adherence of E. coli 0157:H7 on non-wounded greenhouse-grown Romaine lettuce over 72 hours was examined. Data showed, despite increased removal of CFU/Ieaf, an infectious dose remained. Recoveries of E. coli 0157:H7 with P. fluorescens EG3 and E. coli 0157:H7 with P. fluorescens 123 were compared, 88.8% (R2=0.888) of the variance can be explained by the presence of biosurfactant and the effect of time (p<0.05). Approximately 60% and 86% of the variance in the recovery between E. coli 0157:H7 alone, with P. fluorescens EG3, or with P. fluorescens 123,respectively, can be explained by treatment and time (R2=0.597, R2=0.861) (p<0.05).