Browsing by Author "Mosteller, Tracy M."

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    Sanitizer efficacy towards attached bacteria
    Mosteller, Tracy M. (Virginia Tech, 1991)
    Pseudomonas fluorescens, Yersinia enterocolitica, and Listeria monocytogenes readily attach to both rubber and teflon surfaces. Once attached, a glycocalyx covering forms effectively protecting them from any sanitizer that passes over the surface. Therefore, sanitizers efficacy testing done in the laboratory with pure glycocalyx-free cultures could lead to false assumptions as to the sanitizer's true effectiveness under actual use conditions. Our objectives in this study were: (1) evaluate sanitizer efficacy of in use concentrations toward bacteria attached to gasket materials, (2) examine attachment on rubber versus teflon gaskets, (3) examine different methods of enumeration, (4) compare kill of attached bacteria to suspension tests, (5) determine the minimum inhibitory concentrations of Sanitizers. Iodophor, hypochlorite, acid anionic, peroxyacetic acid, fatty acid and QUAT sanitizers failed to provide an adequate log kill of bacteria attached in levels of 10⁴ to 10⁵. Most of the tests showed that the log kill falls well short of a 3 log reduction goal. Plate counts, impedance microbiology, and the direct epifluorescent filter technique were tested as methods of enumeration. Impedance microbiology was the best method of enumeration, since it allows the estimation of both reversibly and irreversibly attached bacteria. Minimum inhibitory concentration tests demonstrated the increased resistance of attached bacteria as compared to cell suspensions.
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    Sanitizer efficacy towards attached bacteria in a simulated milk pipeline system using pure and mixed cultures
    Mosteller, Tracy M. (Virginia Tech, 1993)
    The efficacy of six sanitizers, [chloline (200 ppm), iodophor (2S: ppm), acid anionic (200 ppm), peracetic acid (200 ppm), and fatty acid sanitizer (200 ppm)], was evaluated against bacteria attached to gasket materials. Pseudomonas fluorescens, Yersinia enterocolitica, Bacillus cereus, and Listeria monocvtogenes were capable of significant attachment to both buna-N nlbber and Teflon® gasket surfaces in either pure or mixed cultures. Differences in initial attachment rates were evident in a mixed culture of P. fluorescens, Y. enterocolitica, and Listeria monocytogenes in vitro. Sanitizer effectiveness depended upon the bacterium being enumerated, the type of surface, if the bacterium was attached in pure culture or as part of a mixed culture, and the system of evaluation, (i.e. whether or not sanitizer was used alone or as part of a cleaning system). Peracetic acid was the most effective. Removal of bacteria was more pronounced on the Te'f1on® surface with all sanitizers used. The cleaning system, which consisted of a pre-rinse with warm water, application of the cleaning solution, post-rinse with warm water, and application of the sanitizing solution, allowed microorganisms to remain, when the bacteria were present as a pure culture, but resulted in the complete removal of bacteria in mixed culture.