Romer Labs RapidChek®Listeria monocytogenes Test System for the Detection of L. monocytogenes on Selected Foods and Environmental Surfaces

Juck, Gregory; Gonzalez, Verapaz; Allen, Ann-Christine Olsson; Sutzko, Meredith; Seward, Kody; Muldoon, Mark T.

doi:10.5740/jaoacint.18-0035

Cited by 3 publications

(1 citation statement)

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“…We followed Microbiological Method Validation Guidelines of AOAC International [ 24 ] by desiccating Lm cells on stainless steel surfaces for 16–18 h. This protocol was also referred to in the recently published ISO method validation standards (ISO 16140-2) [ 25 ]. This approach allows relatively straightforward replication and has been used to validate a variety of methods for environmental sampling of foodborne pathogens [ 31 – 33 ]. Even though this desiccation process was not sufficient for Lm to form mature biofilms [ 34 ], it induced desiccation of Lm on stainless steel surfaces that could be used to evaluate the efficacy of enrichment schemes to resuscitate stressed Lm [ 26 ].…”

Section: Resultsmentioning

confidence: 99%

Comparison of three neutralizing broths for environmental sampling of low levels of Listeria monocytogenes desiccated on stainless steel surfaces and exposed to quaternary ammonium compounds

Xian

Kwon

et al. 2020

BMC Microbiol

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Background An effective environmental sampling method involves the use of a transport/neutralizing broth with the ability to neutralize sanitizer residues that are collected during sampling and to maintain viability of stressed Listeria monocytogenes (Lm) cells. Results We applied Lm onto stainless steel surfaces and then subjected Lm to desiccation stress for 16–18 h at room temperature (RT, 21–24 °C). This was followed by the subsequent application of Whisper™ V, a quaternary ammonium compound (QAC)-based sanitizer, diluted to 400 ppm and 8000 ppm of active quat, for 6 h. We then sampled Lm with sponges pre-moistened in three transport broths, Dey/Engley (D/E) broth, Letheen broth and HiCap™ broth, to generate environmental samples that contained sanitizer residues and low levels of stressed Lm, which were subsequently analyzed by an enrichment-based method. This scheme conformed with validation guidelines of AOAC International by using 20 environmental test portions per broth that contained low levels of Lm such that not all test portions were positive (i.e., fractional positive). We showed that D/E broth, Letheen broth and HiCap™ broth performed similarly when no quat or 400 ppm of quat was applied to the Lm contaminating stainless steel surfaces. However, when 8000 ppm of quat was applied, Letheen broth did not effectively neutralize the QAC in the samples. These comparisons were performed on samples stored under three conditions after collection to replicate scenarios of sample transport, RT for 2 h, 4 °C for 24 h and 4 °C for 72 h. Comparisons under the three different scenarios generally reached the same conclusions. In addition, we further demonstrated that storing Letheen and HiCap™ broths at RT for two months before sampling did not reduce their capacity to neutralize sanitizers. Conclusions We developed a scheme to evaluate the ability of transport broths to neutralize QAC sanitizers. The three transport broths performed similarly with a commonly used concentration of quat, but Letheen broth could not effectively neutralize a very high concentration of QAC. The performance of transport broths was not significantly affected under the assessed pre-sampling and post-sampling storage conditions.

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