Listeria monocytogenes (L. monocytogenes) make people and animals have Listeria disease. After infection, the main symptoms of Listeria disease are sepsis, meningitis and mononucleosis. For this purpose, a visual detection of L. monocytogenes was developed with unmodified gold nanoparticles. The species-specific probes, in the presence of PCR target products of L. monocytogenes, cause the gold nanoparticles to aggregate irreversibly, producing a red to purple colorimetric change. As little as 1.304 fg/µl of DNA of L. monocytogenes were thus detected visually, by the naked eye, without the need for any sophisticated, expensive instrumentation and biochemical reagents, which was approximately seventy-fold higher sensitivity over conventional PCR gel electrophoresis method. The results indicate that this assay is highly species-specific, simple, low-cost, and visual for easy detection of L. monocytogenes.
Loop‐mediated isothermal amplification (LAMP) based on lmo0460 sequence in genome of Listeria monocytogenes (L. monocytogenes) was designed for detection of L. monocytogenes, which is an important foodborne kind of pathogenic bacteria causing human and animal disease. The primers set for lmo0460 sequence encoding membrane‐associated lipoprotein consist of four specific primers targeting six regions on specific fragment. The LAMP assay could be optimized and the optimum condition was in 50 min at 63°C. Amplification products were visualized by 2% agarose gel electrophoresis. Sensitivity of the LAMP assay for detection of L. monocytogenes in pure cultures was 1.7 cfu per reaction. The LAMP assay was 147‐fold higher sensitive than that of the conventional polymerase chain reaction (PCR) assay (251 cfu/reaction). Fifty chicken samples were detected for L. monocytogenes in the method, and the accuracy of LAMP was shown to be 100% when compared with culture biotechnical, while the PCR assay failed to detect L. monocytogenes in one of the positive samples. It is shown that LAMP assay based on lmo0460 sequence can be a highly sensitive, efficient and easy‐to‐perform useful detection tool for L. monocytogenes and will be a potential useful and powerful tool for detection foodborne pathogens.
Practical Applications
L. monocytogenes contamination in chicken samples has been reported. In developing countries, such as China, the LAMP assay is a suitable, useful tool for rapid detection of L. monocytogenes in food because it is more cost‐effective, simple and high sensitive than PCR.
A quick, easy, cheap, effective, rugged, and safe extraction approach and gas chromatography/tandem mass spectrometry with programmed temperature vaporization sampling technology were used to determine fungicide quintozene and its hazardous impurity hexachlorobenzene (HCB) in Panax notoginseng root, which is commonly used as a rare traditional Chinese medicine worldwide. The mean recoveries were in the ranges of 94-125 and 84-119% for quintozene and HCB with relative standard deviations of 6.2-16.1% at three concentrations: 0.01, 0.1 and 1 mg kg . Heavy metals arsenic, cadmium, copper and lead were simultaneously detected by an inductively coupled plasma-mass spectrometry approach after digestion with nitric acid. The above methods were used to analyze 50 samples of P. notoginseng roots collected at markets and planting bases from the special local producing areas, namely, Honghe, Kunming and Wenshan in Yunnan province, China. Quintozene and HCB in root samples were determined at <0.0015-1.50 and <0.0015-0.125 mg kg . In the 50 samples, 60, 16, 56, 2 and 6% exceeded the maximum permissible levels in medicinal plants (WM/T2-2004) for quintozene, arsenic, cadmium, lead and copper. The results showed that the method is robust and suitable for measuring quintozene, its hazardous impurity and heavy metals in P. notoginseng roots.
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