This study was conducted to evaluate the abilities of five neutralizing agents, Dey-Engley (DE) neutralizing broth (single or double strength), morpholinepropanesulfonic acid (MOPS) buffer, phosphate-buffered saline (PBS), and sodium thiosulfate buffer, in mitigating the activities of acetic or lactic acid (2%) and an alkaline or acidic sanitizer (a manufacturer-recommended concentration) againt the cells of Shiga toxin-producing Escherichia coli (STEC; n = 9). To evaluate the possible toxicity of the neutralizing agents to the STEC cells, each STEC strain was exposed to each of the neutralizing agents at room temperature for 10 min. Neutralizing efficacy was evaluated by placing each STEC strain in a mixture of sanitizer and neutralizer under the same conditions. The neutralizing agents had no detectable toxic effect on the STEC strains. PBS was least effective for neutralizing the activity of selected organic acids and sanitizers. Single-strength DE and sodium thiosulfate neutralized the activity of both acetic and lactic acids. MOPS buffer neutralized the activity of acetic acid and lactic acid against six and five STEC strains, respectively. All neutralizing agents, except double-strength DE broth, had a limited neutralizing effect on the activity of the commercial sanitizers used in the study. The double-strength DE broth effectively neutralized the activity of the two commercial sanitizers with no detectable toxic effects on STEC cells.

Biofilms are a mixture of bacteria and extracellular products secreted by bacterial cells and are of great concern to the food industry because they offer physical, mechanical, and biological protection to bacterial cells. This study was conducted to quantify biofilms formed by different Shiga toxin-producing Escherichia coli (STEC) strains on polystyrene and stainless steel surfaces and to determine the effectiveness of sanitizing treatments in control of these biofilms. STEC producing various amounts of cellulose (n = 6) or curli (n = 6) were allowed to develop biofilms on polystyrene and stainless steel surfaces at 28°C for 7 days. The biofilms were treated with 2% acetic or lactic acid and manufacturer-recommended concentrations of acidic or alkaline sanitizers, and residual biofilms were quantified. Treatments with the acidic and alkaline sanitizers were more effective than those with the organic acids for removing the biofilms. Compared with their counterparts, cells expressing a greater amount of cellulose or curli formed more biofilm mass and had greater residual mass after sanitizing treatments on polystyrene than on stainless steel. Research suggests that the organic acids and sanitizers used in the present study differed in their ability to control biofilms. Bacterial surface components and cell contact surfaces can influence both biofilm formation and the efficacy of sanitizing treatments. These results provide additional information on control of biofilms formed by STEC.

This study was undertaken to evaluate the microbial quality of the soft drinks served by fast food restaurants and gas station convenience stores in Griffin, GA, and surrounding areas. The soft drinks were collected from the dispensing machines in 8 fast food restaurants or gas station convenience stores in 2005 (n = 25) and in 10 fast food restaurants or gas station convenience stores in 2006 (n = 43) and 2007 (n = 43). One hundred milliliters of each soft drink was filtered through a hydrophobic grid membrane filter. The remaining portion of the soft drink was kept at room temperature for 4 h before sampling in order to mimic the possible holding time between purchase and consumption. The membrane filters were sampled for total aerobic bacteria, Enterobacteriaceae, lactic acid bacteria, and yeasts and molds. The microbial counts in the 2006 samples were numerically higher than the counts in the 2007 samples except for the average lactic acid bacteria counts, and were either significantly or numerically higher than the counts in the 2005 samples. Soft drinks sampled after the 4-h holding period had relatively higher counts than those sampled initially, with a few exceptions. Some soft drinks had over 4 log CFU/100 ml of total aerobic bacteria, Enterobacteriaceae, lactic acid bacteria, and yeast and mold cells. The study revealed the microbial quality of soft drinks served by dispensing machines in Griffin, GA, and surrounding areas, emphasizing the importance of effective sanitizing practice in retail settings.

Some Shiga toxin-producing Escherichia coli (STEC) strains produce extracellular cellulose, a long polymer of glucose with ␤-1-4 glycosidic bonds. This study evaluated the efficacies of selected enzymatic and chemical treatments in inactivating STEC and degrading/removing the cellulose on STEC surfaces. Six celluloseproducing STEC strains were treated with cellulase (0.51 to 3.83 U/15 ml), acetic and lactic acids (2 and 4%), as well as an acidic and alkaline sanitizer (manufacturers' recommended concentrations) under appropriate conditions. Following each treatment, residual amounts of cellulose and surviving populations of STEC were determined. Treatments with acetic and lactic acids significantly (P < 0.05) reduced the populations of STEC, and those with lactic acid also significantly decreased the amounts of cellulose on STEC. The residual amounts of cellulose on STEC positively correlated to the surviving populations of STEC after the treatments with the organic acids (r ‫؍‬ 0.64 to 0.94), and the significance of the correlations ranged from 83 to 99%. Treatments with cellulase and the sanitizers both degraded cellulose. However, treatments with cellulase had no influence on the fate of STEC, and those with the sanitizers reduced STEC cell populations to undetectable levels. Thus, the correlations between the residual amounts of cellulose and the surviving populations of STEC caused by these two treatments were not observed. The results suggest that the selected enzymatic and chemical agents degraded and removed the cellulose on STEC surfaces, and the treatments with organic acids and sanitizers also inactivated STEC cells. The amounts of cellulose produced by STEC strains appear to affect their susceptibilities to certain sanitizing treatments.Shiga toxin-producing Escherichia coli (STEC) strains are enteropathogens producing one or more toxins related to the Shiga toxins of Shigella dysenteriae serotype 1 (15,19,20). The pathogens cause human illness ranging from mild diarrhea to severe hemorrhagic colitis and hemolytic uremic syndrome (3,11,16,21). The reservoirs of STEC are ruminants such as cattle, sheep, goats, etc., but cattle have been identified as the predominant source of STEC (1, 17). STEC infection can be transmitted through contaminated foods, especially raw and undercooked foods of animal origin (6,17,18,33).Cells of certain STEC strains produce cellulose as an extracellular component (5, 45). The cellulose is a long polymer of glucose, which is insoluble and inelastic, and has a high tensile strength (23, 44). The polymer forms subfibrils and crystallizes into microfibrils (12). The fibrils subsequently build insoluble layered sheets and form hydrogen-bonding networks (23). Cellulose-producing and other bacteria can be entrapped in the networks formed by the cellulose polymers (23, 41).Cellulose is viscous and hydrophilic and protects bacterial cells from changes in moisture content, acidity, and toxin content in various environments (23). Bacterial cellulose has the capability to hold water ...