Influence of Punctures, Cuts, and Surface Morphologies of Golden Delicious Apples on Penetration and Growth of Escherichia coli O157:H7

Abstract

The ability of Escherichia coli O157:H7 to penetrate and grow within punctures, fresh-cut surfaces, and calyces of Golden Delicious apples was investigated. A three-strain cocktail of E. coli O157:H7 resistant to ampicillin was used to inoculate fresh and 48-h-old punctures, fresh-cut surfaces, and open or closed calyces. A concentric cutting procedure was used to evaluate depth of penetration within punctures and prevent cross contamination during sampling. Within 2 h, E. coli O157:H7 penetrated vertically through the fresh punctures and 3.4 mm within the underlying parenchyma. After 48 h, E. coli O157: H7 cells penetrated up to 5.5 mm within the punctures and>2.6 mm horizontally away from fresh punctures. However, 48-h-old punctures did not permit penetration beyond their boundaries. Fresh-cut surfaces permitted up to 2.8 mm penetration after 24 h. Onset of growth of E. coli O157:H7 occurred 4 to 8 h postinoculation on fresh punctures and fresh-cut surfaces with populations increasing by 3 logs after 48 h. E. coli O157:H7 penetrated within calyces regardless of the extent of opening or method of inoculation. However, E. coli O157:H7 was never recovered from the inner core of apples. Computed tomography scan imaging revealed that closed calyces effectively prevented penetration of sodium iodide solutions within the calyx cavity. Lack of solution penetration may explain why sanitizing treatments are ineffective in inactivating microbial cells within the calyx. Understanding the role of morphological differences in permitting or restricting bacterial penetration may lead to development of more effective strategies to enhance the safety of fresh horticultural products.

Rapid quantification of Escherichia coli in food and media using bacteriophage T7 amplification and liquid chromatography-multiple reaction monitoring tandem mass spectrometry

“…Of all recorded outbreaks, an outbreak of E. coli O157:H7 traced to apple juice in 1996 caused the most damage involving people from three states in the British Columbia. E. coli has since been shown to survive and propagate in damaged apple tissue (Dingman, 2000;Fatemi et al, 2006). Pierce et al (2012) also made use of isotope-labeled lytic bacteriophage 53 to specifically detect Staphylococcus aureus.…”

Whole surface image reconstruction for machine vision inspection of fruit

“…When fecal material comes in contact with defect sites of an apple (such as cuts and punctures) conditions are favorable for growth of pathogenic bacteria such as E. coli O157:H7 (Fatemi et al, 2006). This is doubly problematic in that pathogenic cells once internalized in fruit not only may grow more rapidly but are also less likely to be affected by sanitizers (in contrast to pathogens that can be killed or washed away on the surface of the fruit).…”

“…The dust may come from nearby fields that have been fertilized with raw untreated cattle manure. In addition, microorganisms can enter the natural openings of apples as well as cut surfaces (Fatemi et al, 2006;Mendonca, 2005 Equally noteworthy is that washes have also proven ineffective at sanitizing these stem and calyx areas. For example, after apples were washed in water that contained bubbling ozone gas, counts of E.coli O157:H7 were reduced from the apple surface but not significantly from the stem/calyx (Achen & Yousef, 2001).…”

“…Microbial growth can be accelerated inside defects such as lesions, cuts, and bruises on the fruit surface (Fatemi et al, 2006). When fecal material comes in contact with defect sites of an apple (such as cuts and punctures) conditions are favorable for growth of pathogenic bacteria such as E. coli O157:H7 (Fatemi et al, 2006).…”

“…Images of objects from curved mirrors 30 Table 5. Percentage of imaging area 34 open skin cuts and bruises may become sites for microbial attack (Fatemi et al, 2006).…”