Performance Evaluation of Easy Plate™ LS for Selective Detection of Listeria Species

Introduction:

Listeria monocytogenes is one of the major foodborne pathogens responsible for listeriosis through contaminated food. Environmental monitoring for Listeria species plays a critical role in preventing contamination and controlling the presence of L. monocytogenes. The newly developed ready-to-use (RTU) medium, Easy Plate™ LS, is convenient, environmentally friendly, and enables rapid detection and enumeration of Listeria species within just 24 hours.

Purpose:

The selectivity of Easy Plate™ LS was evaluated and compared with three conventional agar media (ALOA, PALCAM, and a chromogenic agar) and two commercially available RTU media (RTU-A and RTU-B). The inclusivity study included 28 Listeria monocytogenes strains and 20 strains of other Listeria species, while the exclusivity study evaluated 28 non-target strains. Each strain was enriched overnight, diluted in BPW, inoculated at approximately 100 CFU per plate, and incubated at 35 or 37°C for 24, 28, and 48 hours.

Result:

All L. monocytogenes strains were successfully detected on every medium within 24 hours. For other Listeria species, Easy Plate™ LS achieved growth rates of 75% (15/20) at 24 hours and 85% (17/20) at 28 hours, outperforming the two comparator RTU media, which showed approximately 50% recovery at 24 hours. ALOA demonstrated the highest recovery at 90% (18/20), while PALCAM and the chromogenic agar achieved 65–70% recovery at 24 hours. Some species, including L. seeligeri, L. ivanovii, and L. grayi, required extended incubation for optimal recovery. In the exclusivity study, Easy Plate™ LS, RTU-A, and ALOA showed no growth of non-target strains up to 48 hours, whereas prolonged incubation on some other media resulted in the growth of Enterococcus and Bacillus species.

Significance:

Easy Plate™ LS demonstrated high selectivity and reliable detection of Listeria species while minimizing false-positive growth from non-target microorganisms. By eliminating the need for complex media preparation and providing rapid results within 24 hours, Easy Plate™ LS is expected to improve the efficiency and reliability of environmental monitoring programs for Listeria in food production facilities.

【Product】

• New product　New Lumitester
• New product　New LuciPac
• Lumitester Smart
• LuciPac A3 series
• Easy Plate

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Comparative Performance of Easy Plate AC-R for Rapid Aerobic Bacteria Count in Multiple Food Types

Introduction:

The aerobic plate count is crucial in food microbiological testing, but traditional methods such as Plate Count Agar (PCA) take 48 hours for enumeration. The newly developed ready-to-use (RTU) media for aerobic bacteria count, Easy Plate AC-R (RTU-A) byKikkoman Biochemifa Company, are convenient and environmentally friendly, and allow for rapid enumeration in just 24 hours.

Purpose:

The enumeration performance of RTU-A, PCA, and three other RTU media (RTU-X, RTU-Y, RTU-Z) was compared using various commercially available food samples. Method: Sixty-four food matrices, including meats, seafoods, vegetables, fruits, dairy products, and prepared foods such as RTE foods and dried foods, were used for evaluation. Each medium was inoculated with 1 mL of food dilution and incubated at 35±1 °C. Colony counts were performed visually at 24±1 hours for RTU media and at 48±2 hours for PCA. Counts for RTU-A were performed not only visually but also using Colony Counting System (CCS).

Result:

The correlation coefficients between RTU-A and PCA, as well as RTU-X, RTU-Y, and RTU-Z, were 0.986, 0.990, 0.993, and 0.996, respectively. RTU-A demonstrated equivalent enumeration performance to PCA at 48 hours incubation, with comparable results achieved in just 24 hours. in addition, the correlation coefficient between visual colony counts and those obtained by CCS for RTU-A was 0.979. CCS tended to detect higher numbers of colonies compared to visual counting, confirming its ability to accurately count small and pale colonies.

Significance:

The newly developed RTU-A has demonstrated the ability to perform aerobic bacteria count in significantly less time than conventional PCA methods. When combined with CCS, it is expected to further reduce operator workload, standardize processes and improve traceability.