{"id":244,"date":"2021-02-08T01:27:45","date_gmt":"2021-02-08T06:27:45","guid":{"rendered":"https:\/\/www.cd-bioparticles.com\/blog\/?p=244"},"modified":"2021-02-08T01:27:45","modified_gmt":"2021-02-08T06:27:45","slug":"how-do-you-test-staphylococcus-aureus","status":"publish","type":"post","link":"https:\/\/www.cd-bioparticles.com\/blog\/magnetic-beads\/how-do-you-test-staphylococcus-aureus\/","title":{"rendered":"How Do You Test Staphylococcus aureus?"},"content":{"rendered":"\n
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Staphylococcus\naureus<\/em> is an important pathogen causing suppurative\ninfection in humans and animals, and it is also one of the common pathogens\ncausing human food poisoning. Staphylococcus aureus<\/em> is widely\ndistributed in nature, such as air, soil, water, and other environments. This\nbacteria is also often found on the skin of humans and animals and in the\ncavities communicating with the external environment. It is reported that the\ncarrying rate of bacteria in normal people can reach 30% to 80%, of which the\ncarrying rate of skin is 8% to 22%, and that of the upper respiratory tracts\nsuch as nose and throat is more than 40% or 50%. Thus, food can be contaminated\nby Staphylococcus aureus<\/em> via various ways and means, especially through\nthe hands and upper respiratory tract of food processors. As pathogenic Staphylococcus\naureus<\/em> can produce enterotoxins, once it contaminates food and in a\nsuitable temperature environment, it can reproduce and form massive\nenterotoxins, thus causing food poisoning to consumers.<\/p>\n\n\n\n

Food poisoning\ncaused by Staphylococcus aureus<\/em> is very common in countries all over the\nworld. Especially in North America and Europe, the incidence is higher. In\nthese countries, there are cases of food poisoning caused by Staphylococcus\naureus<\/em> every year, ranking second to third in the number of cases of\nbacterial food poisoning. The economic loss caused by this is also quite heavy,\nso at present, worldwide countries have listed Staphylococcus aureus<\/em> as\na legal inspection item for food hygiene.<\/p>\n\n\n\n

Over the years,\nmany food microbiology laboratories have been exploring and seeking more\naccurate and rapid detection methods. By now, the rapid detection methods of Staphylococcus\naureus<\/em> can be classed into three types: rapid detection based on 1)\nculture, 2) immunology and 3) nucleic acid-based molecular biology.<\/p>\n\n\n\n

1. Culture\nmethod<\/p>\n\n\n\n

1.1 Detection\nusing chromogenic\/fluorogenic culture media<\/p>\n\n\n\n

Chromogenic\/fluorogenic\nculture media is a new type of medium in which enzymes produced by\nmicroorganisms’ own metabolism can react with the corresponding chromogenic\nsubstrate to detect microorganisms, reducing the need for pure culture and\nfurther biochemical identification of strains.<\/p>\n\n\n\n

1.2 Detection\nusing count plates<\/p>\n\n\n\n

The\nexistence of Staphylococcus aureus<\/em> was detected by the reaction of\nheat-stable nuclease produced by Staphylococcus aureus<\/em> in the process of\nculture and chromogenic agent to form a pink ring on the count plate. Count\nplates consist of two parts, one is a highly selective medium for Staphylococcus\naureus<\/em>, and the other is a reaction tablet containing the chromogenic agent\nand deoxyribonucleic acid (DNA). These commercial count plates have high\nspecificity and a short detection time.<\/p>\n\n\n\n

2. Immunology\nmethod<\/p>\n\n\n\n

This method\nuses the specific interaction between antigen and antibody as the theoretical\nbasis for the detection of Staphylococcus aureus<\/em>. It is characterized by\nsimple operation, strong specificity, and high sensitivity, and is suitable for\nthe detection of a large number of samples.<\/p>\n\n\n\n

2.1\nELISA<\/p>\n\n\n\n

Enzyme-Linked\nImmunosorbent Assay (ELISA) is the most commonly used method in\nimmunodiagnosis, and the sandwich ELISA is often applied in the detection of Staphylococcus\naureus<\/em>. This method can detect Staphylococcus aureus<\/em> enterotoxin\nwithin 15 min. However, it also has some defects, for example, the reagents\nused in the test are high-quality and expensive, and are easily affected by\nenvironment, temperature, time, and other conditions.<\/p>\n\n\n\n

2.2 IFA<\/p>\n\n\n\n

Immunofluorescence\nassay (IFA) is used to detect Staphylococcus aureus<\/em> by specific binding\nof antigen and antibody. The known antibody is conjugated with fluorescent\npigment to form a fluorescent marker, and under specific conditions, the sample\nwill react with it, and then the existence of the fluorescent-labeled antigen-antibody\ncomplex is observed under a fluorescence microscope. If so, it is proved that\nthe sample contains Staphylococcus aureus<\/em>. Compared with the traditional\nmethod, the detection time of this method is greatly shortened, and the whole\nprocess takes 40-50 min.<\/p>\n\n\n\n

2.3 RPLA<\/p>\n\n\n\n

Reverse\npassive latex agglutination (RPLA) is based on the principle of an indirect\nagglutination reaction. The specific antibody is adsorbed on the latex\nparticles and when the antigen and antibody bind specifically, the latex\nparticles agglutination occurs. The degree of agglutination is proportional to\nthe content of bacteria in the sample to be tested. Although RPLA is simple and\neasy, the sensitized latex is prone to self-agglutination, which affects the\nsensitivity of the reaction and results in inaccurate detection results.<\/p>\n\n\n\n

3. Molecular method<\/p>\n\n\n\n

3.1 PCR<\/p>\n\n\n\n

This\nmethod overcomes the shortcomings of traditional detection methods, and has\ndeveloped rapidly in recent years, and has been applied in many fields. It was\nfirst reported that the PCR method was used to detect Staphylococcus aureus<\/em>\nin food in 1991. Wilson et al successfully detected Staphylococcus aureus<\/em>\nenterotoxin B and C1 in artificially contaminated dried skimmed milk samples\nwithin 8 hours, and the detection limit of target DNA was 1 fg.<\/p>\n\n\n\n

3.2 Gene chip<\/p>\n\n\n\n

Gene chip\ntechnology is a novel technology of reverse solid phase hybridization, which\nhas the characteristics of high throughput, speed, and sensitivity. Its\nprinciple is to design an oligonucleotide probe for detecting Staphylococcus\naureus<\/em> and fix it on the nitric acid membrane in a certain way. The target\ngene is amplified and labeled by primers and hybridized with the gene chip\nunder appropriate conditions, and the existence of Staphylococcus aureus<\/em>\nis identified according to the hybridization results. This method has good\nspecificity, high accuracy, and strong maneuverability, and can provide a\nstrong basis for clinical treatment.<\/p>\n\n\n\n

3.3\nLAMP<\/p>\n\n\n\n

In the\nloop-mediated isothermal amplification (LAMP) technique, four specific primers\nare designed for 6 regions of the target gene, and strand-displacing DNA\npolymerase is used to react under isothermal conditions. The amplification\ncould be completed within 1 hour, showing LAMP typical ladder bands, and the\namplification results could be judged by naked eye observation. The LAMP does\nnot need expensive instruments and is fast, sensitive, specific, and low cost.<\/p>\n\n\n\n

Recently,\nLee et al. developed a fast, ultra-sensitive, high-precision POCT device for\nthe detection of the pathogenic bacteria Staphylococcus aureus<\/em>. The\ndevice is based on the “count-on-a-cartridge” (COC) platform, which\nminimizes complex user interventions and maximizes the detection accuracy with\na lower detection limit.<\/p>\n\n\n\n

\u201cWe combined a high-throughput microfluidic-based immunomagnetic concentration process using magnetic particles (MPs) conjugated with an antibody probe with a cartridge capable of autonomously separating out and capturing a small number of magnetically and fluorescently labeled (using a quorum-based modified autoinducing peptide (mAIP) probe) bacteria from a great number of free unbound MPs within a passively regulated controlled time after concentration.\u201d Professor Lee said. MP-SAab<\/sub> (WHM-G048<\/a>, CD Bioparticles) and anti-Staphylococcus aureus<\/em> antibody were used to bind with target bacterial cells. The system is composed of a magnetic concentrator, sensing cartridge, and fluorescent image reader with a built-in counting algorithm. Results can be obtained within a few hours in a user-friendly manner, with high sensitivity and high precision. The analytical performance of this assay is comparable to that of standard plates. According to the global microbiological standards for Staphylococcus aureus<\/em>, COC analysis shows that the sensitivity is 92.9%, and the specificity is 100%, which is acceptable below 100 CFU\/g in the food matrix. This culture-independent, fast, ultra-sensitive, and highly accurate COC analysis method has great potential in places where bacterial monitoring is urgently needed. <\/p>\n\n\n\n

References:
1. Lee, W. I., Park, Y., Shrivastava, S., Jung, T., Meeseepong, M., Lee, J., … & Lee, N. E. (2020). A fully integrated bacterial pathogen detection system based on count-on-a-cartridge platform for rapid, ultrasensitive, highly accurate and culture-free assay. Biosensors and Bioelectronics<\/em>, 152, 112007.
2. Wilson, I. G., Cooper, J. E., & Gilmour, A. (1991). Detection of enterotoxigenic Staphylococcus aureus in dried skimmed milk: use of the polymerase chain reaction for amplification and detection of staphylococcal enterotoxin genes entB and entC1 and the thermonuclease gene nuc. Applied and environmental microbiology<\/em>, 57(6), 1793-1798. <\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"

Staphylococcus aureus is an important pathogen causing suppurative infection in humans and animals, and it is also one of the<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,6],"tags":[4,65,66],"class_list":["post-244","post","type-post","status-publish","format-standard","hentry","category-applications","category-magnetic-beads","tag-magnetic-particles","tag-protein-a-magnetic-particles","tag-staphylococcus-aureus"],"_links":{"self":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/244","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/comments?post=244"}],"version-history":[{"count":1,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/244\/revisions"}],"predecessor-version":[{"id":246,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/posts\/244\/revisions\/246"}],"wp:attachment":[{"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/media?parent=244"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/categories?post=244"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cd-bioparticles.com\/blog\/wp-json\/wp\/v2\/tags?post=244"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}