Modeling the Rate of Attachment of Listeria monocytogenes , Pantoea agglomerans , and Pseudomonas fluorescens to, and the Probability of Their Detachment from, Potato Tissue at 10°C

Abstract

The rate of attachment of bacteria to, and their subsequent detachment from, the cut surface of raw potato tissue was measured and modeled by using mathematical approaches that allowed detailed objective comparisons of adhesion processes under different conditions. Attachment was rapid and reached equilibrium after contact for 60 min. A new method to measure the probability of detachment was developed and modeled, revealing that the probability of detachment for Pseudomonas fluorescens remained unchanged for contact times between less than 5 s and 60 min. Listeria monocytogenes, however, was more easily removed initially, with the probability of detachment decreasing over the first 2 min of contact but remaining constant and equivalent to that for Pseudomonas fluorescens thereafter. For all of the bacteria tested, the number of bacteria attached after 2 min of contact was proportional to the inoculum concentration raised to the power of 0.79.There is a growing body of literature reporting the bacterial contamination of ready-to-eat prepared vegetable tissues. Such tissues often become contaminated in the field. Despite postharvest trimming and decontamination processes, this contamination persists during commercial preparation, and the products can contain in excess of 10 6 viable bacteria g Ϫ1 at the time of packing (6). Contaminants are predominantly Pseudomonas spp. and Pantoea spp. (5, 6), but bacteria of public health significance, such as Escherichia coli, Yersinia spp., and Listeria spp., may also be present (1, 4, 5, 12, 14; K. Sizmur and C. W. Walker, Letter, Lancet i:1167, 1988).Scanning electron microscopy of prepared leaf tissues has shown that bacteria can be found on the abaxial and adaxial surfaces. However, the bacteria preferentially occupy the cut surfaces, where they multiply throughout storage of the products to form an extensive layer, sometimes many cells thick (6). Growth of Pseudomonas spp. and Pantoea spp. on cut surfaces is followed by production by these bacteria of an extracellular polysaccharide, creating a protective layer which is resistant to chemical and physical decontamination processes (10). Colonization of the cut surface is a two-stage process; initial adhesion occurs rapidly and is followed by the production of an extracellular polysaccharide by the adhered bacteria.Most studies of colonized vegetable tissue surfaces emphasize the mature biofilm stage, and little work has concerned the initial colonization process. However, commercial decontamination processes are typically applied to prepared vegetable tissues within a few minutes of chopping, shredding, or dicing. These processes usually involve washing in potable water with, in some countries, added biocidal compounds, such as chlorine (11). Such washing occurs considerably before the establishment of the protective extracellular polysaccharide, and yet the washing process still fails to remove all of the bacteria (2, 6, 9, 13).Here we report studies of the measurement and modeling of the rate of adhesion of bacteria to,...

Antilisterial activity of carrots: Effect of temperature and properties of different carrot fractions

“…To detect any possible antilisterial activity during the attachment period, actual initial concentrations on sliced carrots were compared with theoretical values. Such theoretical concentrations have been estimated here from an expression developed for Listeria cells attached to potato disks, which do not show antilisterial activity and were prepared following the same procedure as described here (Garrood et al, 2004). The number of L. monocytogenes cells becoming attached to both sides of the potato disks has been reported in the mentioned work as proportional to the inoculum concentration (expressed as CFU mL -1 ) raised to the power of 0.79 (CFU per potato disk= 1.418 × [inoculum size] 0.79 ).…”

“…After 40 min, enough time for attachment (Garrood, Wilson & Brocklehurst, 2004), batches of ten carrot disks were rinsed in 1 L of sterile PSDF (at 10 or 25°C, respectively) for 1 min, stirring at 150 rpm. The purpose of this step was to simulate the domestic washing and at the same time to remove bacteria that were loosely associated with, but had not adhered to, the carrot tissue.…”

Prevalence, persistence and control of Salmonella and Listeria in shrimp and shrimp products: A review

“…By contrast, studies on Salmonella and Listeria attachment to animal (chicken, beef, pork) food surfaces (Benedict, Schultz, & Jones, 1991;Chung, Dickson, & Crouse, 1989;Notermans & Kampelmacher, 1974;Dickson & Macneil, 1991) have been conducted since the 1970s. More recently studies on the attachment of these bacteria to fruits (Pao & Davis, 2001), vegetables (Barak, Whitehand, & Charkowski, 2002;Ells & Hansen, 2006;Garrood, Wilson, & Brocklehurst, 2004;Gorski, Palumbo, & Mandrell, 2003;Iturriaga, Escartin, Beuchat, & Martinez-Peniche, 2003) and fish (Kim & Marshall, 2001;Kim & Marshall, 2002;Verhaegh, Marshall, & Oh, 1996) have been reported. Although information on the attachment of Salmonella and Listeria to shrimp is very limited, we speculate that the process is similar to that associated with meat and plant products.…”

Role of Attachment to Surfaces on the Prevalence and Survival of Campylobacter through Food Systems

“…Garrood et al (54) found that an increase in time of contact enhanced the attachment of L. monocytogenes, Pantoea agglomerans, and P. fluorescens to potato tissue. Longer contact times also reduced the probability of detachment of bacterial cells from potato surfaces, indicating that the strength of bacterial attachment to surfaces may increase over time (54). For Campylobacter, we recently reported that increasing temperature and time of contact both increases the numbers of C. jejuni cells attaching to stainless steel and decreases the probability of detachment of bacterial cells from this surface (118).…”