MICROBIAL ECOLOGY AND SAFETY OF FRESH ON-FARM ORGANICALLY GROWN PRODUCE
Title: Survival and growth of Escherichia albertii on fresh-cut lettuce stored at various temperatures
| Taylor, T - TEXAS A&M UNIV |
| Taormina, Peter - JOHN MORRELL CO. |
Submitted to: International Association for Food Protection Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2008
Publication Date: August 3, 2008
Citation: Sharma, M., Taylor, T.M., Taormina, P. 2008. Survival and growth of Escherichia albertii on fresh-cut lettuce stored at various temperatures [abstract]. International Association for Food Protection Proceedings 2008 Abstract Book. Paper No. P1-14. p. 57.
Introduction: Escherichia albertii is a potential foodborne pathogen because of its ability to cause diarrheal disease. The behavior of the pathogen in foods, especially produce commodities, has not been widely examined.
Purpose: The behavior of three strains of E. albertii on fresh-cut iceberg lettuce stored at different temperatures was evaluated.
Methods: Three nalidixic acid (Nal)-resistant strains of E. albertii (9194, 10457, and 19982) were spot inoculated on pieces of lettuce (9 cm^2) with 3.22, 2.63, and 5.28 log CFU/ cm^2, respectively, and allowed to dry for 1 hr before being sealed in a petri plate with a wet piece of filter paper and stored at 5 and 15 C (up to 7 days), or 30 C (up to 2 days). Samples were homogenized and then enumerated on selective RMACN (rhamnose MacConkey agar supplemented with Nal) at appropriate times for enumeration. Two replicate experiments of each strain on cut lettuce were performed, and significant differences (P<0.05) between strains were determined.
Results: After 7 days of storage at 5 C, strains 10457 and 19982 decreased by 0.78 and 1.56 log CFU/ cm^2, respectively, while strain 9194 increased by 0.52 log CFU/ cm^2. After 7 days at 15 C, strain 9194 was significantly greater (5.16 log CFU/ cm^2) than strains 10457 and 19982 (4.48 and 4.28 log CFU/ cm^2), respectively. At 30 C, strain 9194 (6.24 log CFU/ cm^2) was significantly greater than strain 10457 (5.82 log CFU/ cm^2). After 7 days of storage, all strains grew by at least 0.70 log CFU/ cm^2 and 2.31 log CFU/ cm^2 at 15 and 30 C, respectively.
Significance: Strain 9194 showed marginal growth when stored at 5 C, indicating that this strain of E. albertii may be more persistent at low temperatures than other strains. As expected, all strains of E. albertii grew on lettuce at abusive temperatures. This is the first examination of E. albertii on fresh cut produce.