Hello, my partner! Let's explore the mining machine together!

[email protected]

method method of magnetic separation in wikipedia

magnetic separation methods | article about magnetic separation methods by the free dictionary

magnetic separation methods | article about magnetic separation methods by the free dictionary

All materials possess magnetic properties. Substances that have a greater permeability than air are classified as paramagnetic; those with a lower permeability are called diamagnetic. Paramagnetic materials are attracted to a magnet; diamagnetic substances are repelled. Very strongly paramagnetic materials can be separated from weakly or nonmagnetic materials by the use of low-intensity magnetic separators. Minerals such as hematite, limonite, and garnet are weakly magnetic and can be separated from nonmagnetics by the use of high-intensity separators.

Magnetic separators are widely used to remove tramp iron from ores being crushed, to remove contaminating magnetics from food and industrial products, to recover magnetite and ferrosilicon in the float-sink methods of ore concentration, and to upgrade or concentrate ores. Magnetic separators are extensively used to concentrate ores, particularly iron ores, when one of the principal constituents is magnetic. See Mechanical separation techniques, Ore dressing

All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.

magnetic separation method

magnetic separation method

Magnetic separation is a process used to separate materials from those that are less or nonmagnetic. All materials have a response when placed in a magnetic field, although with most, the effect is too slight to be detected. The few materials that are strongly affected (magnetised) by magnetic fields are known as Ferromagnetics, those lesser (though noticeably) affected are known as Paramagnetics.

Ferromagnetics require relatively weak magnetic fields to be attracted and devices to separate these materials usually have magnets that are permanently magnetised (Permanent magnets do not require electricity to maintain their magnetic fields). Paramagnetics require stronger magnetic fields and these can only be achieved and maintained by electro magnets (large wire coils around an iron frame current is continuously passed through the coils creating the magnetic field within the iron. The field is concentrated across an air gap in the circuit).

Both ferromagnetic (low intensity) and paramagnetic (high intensity) separation devices (Laboratory Magnetic Separator) may be operated with dry solids or with solids in pulp form. (A complete classification of magnetic separating devices is given in Wills Mineral Processing Technology, pp. 338-356).

(*The units given are kilogauss (kG). These are the units most commonly used. The equivalent S.I. unit is the Tesla (T) * 1 Tesla = 10 kilogauss). The extremes of field strength used are based on experience from a magnetic separation testing laboratory over many years.

methods of separation - learn various separation techniques with examples

methods of separation - learn various separation techniques with examples

Most of the time the substances that we see around us are not in their pure form. They are basically a mixture of two or more substances. Interestingly, mixtures tend to also come in different forms. Therefore, there are several types of separation techniques that are used in segregating a mixture of substances. As for the need for separation, it is usually done to remove all the unwanted materials and obtain useful components.

This method involves simply picking out all the unwanted substances by hand and separating them from useful ones. The separated substances may be an impurity that has to be thrown away or maybe that both the separated substances are useful. For example if you separate black grapes from green ones from a mixture of the two.

This method is mostly done during the harvesting of crops. Normally, the stalks of the wheat are dried once it is harvested. The grain is then separated from the stalks and grounded into the floor by beating the dry stalks to shake off the dried grains.

When the grains are collected from the process of threshing, it needs to be cleared out of husks and chaffs before it is turned into flour. Normally the separation of the mixture is carried out with the help of wind or blowing air. The husk and chaff are blown away by the strong wind when the farmers drop the mixture from a certain height to the ground. The heavier grains are collected at one place.

It is done to separate mixtures that contain substances mostly of different sizes. The mixture is passed through the pores of the sieve. All the smaller substances pass through easily while the bigger components of the mixture are retained.

Evaporation is a technique that is used in separating a mixture usually a solution of a solvent and a soluble solid. In this method, the solution is heated until the organic solvent evaporates where it turns into a gas and mostly leaves behind the solid residue.

When mixtures consist of two or more pure liquids than distillation is used. Here the components of a liquid mixture are vaporized, condensed and then isolated. The mixture is heated and the component which is volatile vaporizes first. The vapour moves through a condenser and is collected in a liquid state.

The most common method of separating a liquid from an insoluble solid is the filtration. Take, for example, the mixture of sand and water. Filtration is used here to remove solid particles from the liquid. Various filtering agents are normally used like filtering paper or other materials.

Separating funnel is used mainly to segregate two immiscible liquids. The mechanism involves taking advantage of the unequal density of the particles in the mixture. Oil and water can be easily separated using this technique.

Frequently Asked Questions FAQsWhat are chemical methods of separation? Distillation, crystallisation, adsorption, membrane procedures, absorption and stripping, and oxidation are the typical chemical engineering methods of isolation and purification. How can you separate sand and salt? It either remains in the bath as sand is applied to the bath or forms a film on the bottom of the bottle. Consequently, sand does not dissolve in water and is unsoluble. Through separating the mixture, it is easy to segregate sand and water. Salt by evaporation may be isolated from a solution. What are two types of mixtures? Two types of mixtures exist: heterogeneous and homogeneous. Two or more ingredients (or phases, regions with standardised structure and properties) intermingle in heterogeneous mixtures but remain physically distinct. Is Coca Cola a mixture? Although the sugar and water are blended equally in the solution, Coca cola is a homogeneous mixture. You can also see the basic ingredients in a homogeneous mixture such as coca cola, but heterogeneous means that you can see the basic ingredients such as a salad. Can homogeneous mixtures be separated? Components in homogeneous mixtures can typically be distinguished by taking account of the varying properties of the different components. A mixture can be heated until the component that boils at the lowest temperature becomes a vapour and can be distinguished during the distillation process.

It either remains in the bath as sand is applied to the bath or forms a film on the bottom of the bottle. Consequently, sand does not dissolve in water and is unsoluble. Through separating the mixture, it is easy to segregate sand and water. Salt by evaporation may be isolated from a solution.

Two types of mixtures exist: heterogeneous and homogeneous. Two or more ingredients (or phases, regions with standardised structure and properties) intermingle in heterogeneous mixtures but remain physically distinct.

Although the sugar and water are blended equally in the solution, Coca cola is a homogeneous mixture. You can also see the basic ingredients in a homogeneous mixture such as coca cola, but heterogeneous means that you can see the basic ingredients such as a salad.

Components in homogeneous mixtures can typically be distinguished by taking account of the varying properties of the different components. A mixture can be heated until the component that boils at the lowest temperature becomes a vapour and can be distinguished during the distillation process.

Sedimentation is a physical water treatment process that uses gravity to remove suspended solids from water. Solid particles formed by the turbulence of moving water can be naturally removed by sedimentation in the still water of lakes and oceans.

Decantation is the process of separating liquids, and the potential benefit of decantation is to separate liquid from precipitate. An example of this gain can be seen when making brewed coffee, decanting the blend of coffee, and removing the coffee from the coffee grounds.

Magnetic separation is the process of separating components of mixtures by using magnets to attract magnetic materials. The process that is used for magnetic separation detaches non-magnetic material with those that are magnetic.

magnetic separation methods for the detection of mycobacterium avium subsp. paratuberculosis in various types of matrices: a review

magnetic separation methods for the detection of mycobacterium avium subsp. paratuberculosis in various types of matrices: a review

Marketa Husakova, Radka Dziedzinska, Iva Slana, "Magnetic Separation Methods for the Detection of Mycobacterium avium subsp. paratuberculosis in Various Types of Matrices: A Review", BioMed Research International, vol. 2017, Article ID 5869854, 15 pages, 2017. https://doi.org/10.1155/2017/5869854

The main reasons to improve the detection of Mycobacterium avium subsp. paratuberculosis (MAP) are animal health and monitoring of MAP entering the food chain via meat, milk, and/or dairy products. Different approaches can be used for the detection of MAP, but the use of magnetic separation especially in conjunction with PCR as an end-point detection method has risen in past years. However, the extraction of DNA which is a crucial step prior to PCR detection can be complicated due to the presence of inhibitory substances. Magnetic separation methods involving either antibodies or peptides represent a powerful tool for selective separation of target bacteria from other nontarget microorganisms and inhibitory sample components. These methods enable the concentration of pathogens present in the initial matrix into smaller volume and facilitate the isolation of sufficient quantities of pure DNA. The purpose of this review was to summarize the methods based on the magnetic separation approach that are currently available for the detection of MAP in a broad range of matrices.

Paratuberculosis (Johnes disease) is a chronic granulomatous enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP). The bacterium infects mainly domestic animals such as cattle, sheep, and goats but also wildlife species (e.g., deer) [1]. Animals are usually infected at a young age through contaminated feces, colostrum, and milk or via contaminated feed [2]. The early detection of Johnes disease is difficult because of the long incubation period, which can last 210 years before clinical symptoms appear [3]. The progressive stage of infection is characterized by diarrhea and loss of body weight, which can end in death. This results in lower meat and milk yields, and thus paratuberculosis causes significant financial losses to farmers worldwide [1]. MAP is spread mainly through milk and feces [2]. In 2007, 68.1% of U.S. dairy operations were infected with MAP and the National Animal Health Monitoring System released a report highlighting the importance of this disease [4].

Animals with clinical signs represent only a small proportion of the infected animals within a herd. Those with subclinical disease and thus no clinical symptoms can remain undetected for years during which time, as carriers of MAP, they can shed the infectious agent into the external environment [5, 6]. Successful control of paratuberculosis has been difficult because commonly used diagnostic tests are not accurate until the later stage of infection [7, 8].

Different kinds of matrices, such as feces, milk, milk products, colostrum, environmental samples, milk filters, tissue, or blood can be used for the detection of MAP. Feces and milk represent the most commonly tested matrices. However, due to the presence of many inhibitory substances, the usage of extracted DNA from these test matrices can be complicated. In milk and colostrum, fat and high concentrations of milk protein represent the major problem. Redundant substances from feed, phytic acid, and polysaccharides in feces can inhibit DNA amplification [9, 10]. Thus, appropriate sample preparation prior to PCR detection is crucial. For these purposes, new and more sensitive MAP DNA isolation methods based on magnetic separation procedures (immunomagnetic separation and peptide-mediated magnetic separation) have been developed. Commercially available kits with specific reagents remove PCR inhibitors or have greatly improved DNA capture technology by using DNA or cell-binding paramagnetic beads or DNA filters [11].

The aim of this review is to summarize all of the available information regarding MAP cells and DNA isolation methods based on magnetic separation procedures for the detection of MAP from a broad range of matrices.

There are several methods used for the detection of MAP in infected animals. Cultivation with chemical decontamination was one of the first methods to be developed for MAP detection. Despite the fact that more rapid methods for MAP detection have been reported in recent years, culture is still considered to be the gold standard even though the method is slow (the incubation of MAP on solid medium lasts at least 3 months), is labour intensive, and has limited sensitivity [12].

The popularity of the polymerase chain reaction (PCR) for the detection of MAP has risen in recent years. This method is rapid and sensitive and can be designed very specific for the broad range of different organisms. On the other hand, PCR is very sensitive to the presence of inhibitory substances in samples and when applied directly, sensitivity is very low (especially in milk samples, 23%) [13]. Thus, in any direct PCR the extraction method is a critical step [14]. The majority of PCR protocols for MAP detection target the insertion sequence IS900, F57, HspX, or ISMav2 and ISMap04 [15, 16].

A disadvantage of the PCR methods used for the detection of MAP is that they cannot distinguish between viable and nonviable bacteria in the analyzed samples. For this reason the phage amplification assay method was developed. The commercially available FASTPlaque TB assay enables rapid detection of viable MAP within 2448h based on the count of plaques produced when mycobacteriophage-infected cells burst in a lawn of fast-growing Mycobacterium smegmatis [17]. To obtain sufficient specificity, it is necessary to verify the plaques combining the phage amplification assay with another detection method such as conventional PCR [18]. Peptide-mediated magnetic separation (PMS) can be used prior to phage amplification assay to reduce the complexity of the sample and remove the inhibitors which interfere following PCR, necessarily used for confirmation of specificity [19]. PMS-phage assay can be also combined with ELISA consequently called phage-mediated immunoassay [17].

The identification of paratuberculosis can be achieved either through identification of the infectious agent or on the basis of the hosts immune response (ELISA) [7]. This antibody detection method enables high-throughput and relatively low-cost analysis. However, the sensitivity of MAP-specific ELISA is generally estimated to be below 50%, depends on the stage of disease, and varies between animal species and the tests that are used [20]. The gamma-interferon assay is another immune response detection method used for indirect detection of MAP. This diagnostic test relies on the fact that T-lymphocytes release gamma interferon (INF-) when exposed to specific antigens, and the test measures the amount of released INF- [21, 22]. However, as protein purified derivate used for the stimulation of the immune system includes antigens shared with other mycobacteria, false-positive results can occur [23].

Magnetic separation (MS) methods involving either antibodies or peptides (Figure 1) were developed in order to introduce specificity for efficient MAP capture. MS-based methods selectively separate the target bacteria from other, nontarget microorganisms and inhibitory sample components while concentrating the target bacterial cells into a smaller volume. However, Foddai et al. [24] pointed out that not all magnetic separation approaches developed for the selective concentration of MAP perform equally well. The selectivity of capture is assessed by determining the efficiency of capture and depends on the bead characteristics (composition, size, concentration, and surface modification) or the nature of the coating ligand (polyclonal or monoclonal antibody, biotinylated or nonbiotinylated peptide). Capture efficiency, expressed as a percentage, is a measure of the completeness of capture from the original population of target cells present in the sample. Usage of magnetic separation enhances the analytical specificity and sensitivity of the subsequent detection method, which can be culture, PCR, microscopy, an antigen detection immunoassay, or a phage assay [24].

The major weakness of MS-based methods is nonspecific recovery of other Mycobacterium spp. Foddai et al. [24] described two types of nonspecific recovery. The first type was observed when uncoated beads were used and the percentage of recovery of nontarget mycobacteria was <10%. This is caused by nonspecific interaction between the surface of paramagnetic beads and bacteria, most likely due to electrostatic bonds or van der Waals forces. The second type of nonspecific recovery, which exceeds 10%, is caused by cross-reaction between the coating ligand (peptide or antibody) and usually closely related nontarget bacteria. Issues with nonspecific recovery could be solved by coating the paramagnetic beads with specific ligands.

Combined MS-based techniques are routinely used for the detection and isolation of pathogenic bacteria such as Listeria monocytogenes [25], Salmonella spp. [26], and Escherichia coli [27] in both food and veterinary clinical samples [28]. In mycobacterial research this approach is still not so commonly used.

The immunomagnetic separation (IMS) method relies on the interaction between cell surface antigens and antibodies coated onto paramagnetic beads. The immune part of the beads is represented either by monoclonal or polyclonal antibodies which selectively capture target bacteria. IMS for MAP, first described by Grant et al. [29], employs a rabbit polyclonal anti-MAP antibody, which was used to coat sheep anti-rabbit immunoglobulin G (IgG) type M-280 Dynabeads and facilitates selective isolation of MAP cells from milk. IMS is a powerful method for extracting desired organisms from heterogeneous bacterial suspensions; it shows good detection specificity for MAP and high detection sensitivity, although this is very much dependent on the antibody involved. The speed of MAP detection is enhanced by subsequent IS900 PCR use. Immunomagnetic PCR (IMS-PCR) can detect as little as 103CFU/50mL, which is 1 to 2 log10 units lower compared to the number detected by IS900 PCR applied to milk directly [13]. Use of polyclonal antibody IMS-based methods in conjunction with culture lacks, according to Foddai et al. [24] and sufficient specificity for MAP and nontarget bacteria can overgrow this bacterium in culture. Nevertheless, since no selective medium truly exists, specificity for MAP must be achieved by optimizing the types of beads and capture ligands.

Metzger-Boddien et al. [30] reported a monoclonal antibody IMS-PCR-based method for MAP as a rapid, standardized, and fully automated technique for routine, large scale diagnostic applications. It was shown that this method is very specific and sensitive in detecting minimal amounts of artificially spiked MAP in milk and overall shows superior effectiveness compared to culture.

Most recently, novel monoclonal antibodies for MAP were successfully developed by OBrien et al. [31]. This new IMS approach uses MyOne Tosylactivated Dynabeads dually coated with monoclonal antibodies 6G11 and 15D10 and promises improvement in sensitivity of MAP capture. However, successful application will be dependent on the end-point detection method and the author suggests to use culture or phage amplification assay.

Peptide-mediated magnetic separation (PMS) relies on the interaction between MAP-specific peptides (aMptD, aMp3) coupled with paramagnetic beads and surface-exposed MAP proteins (MptD, Mp3). The 12-mer peptides used were originally identified by phage display biopanning of MAP cells using the Ph.D.-12 phage library and are chemically synthesized to achieve high purity before coating onto paramagnetic beads [32, 33].

PMS can be employed together with other methods such as the phage amplification assay. This combination enables rapid enumeration of viable MAP cells within 24h and is selective for low numbers of MAP. PMS is followed by culture, as a reference method for MAP, but without the need for chemical decontamination [19]. The detection of viable MAP cells and not just MAP DNA is the main advantage of this method over IMS-PCR. Moreover, Foddai et al. [24] reported that the detection sensitivity of the novel automated PMS-phage assay is comparable to or better than those of IMS-PCR methods.

Besides novel monoclonal antibodies, OBrien et al. [31] generated also new peptide ligands specific for MAP cells and suggested new PMS approach using biotin-EEA402 peptide-coated beads. According to the author, both new IMS and PMS approaches were found to improve the sensitivity of MAP capture compared to the currently used aMp3/aMptD peptide-coated beads. However, these systems are currently under the investigation and need to be applied to matrices to verify their reliable function.

In the following paragraphs, we describe the use of individual types of MS for the detection of MAP. This information is summarized in tables divided according to the type of matrix used. Another partitioning criterion was whether MAP cells or DNA are detected by MS.

The isolation of MAP cells from milk is currently performed using either IMS or PMS methods in conjunction with some end-point detection method, most often IS900 PCR, phage assay, ELISA, or culture. The most commonly used type of beads for IMS is M-280 sheep anti-rabbit immunomagnetic Dynabeads coated with polyclonal rabbit anti-MAP antibodies (Table 1). Djnne et al. [34] used Dynabeads and IMS-IS900 PCR for MAP detection in goat milk. The minimal Limit of Detection was determined using unpasteurised cows milk that was artificially contaminated. Using IMS-IS900 PCR, the minimum detection limit for visualization of a product using ethidium bromide was 1CFU/mL (using dot blot even 0.1CFU/mL), in comparison with culture where the minimum detection limit was 10CFU/mL milk. This finding confirms the high sensitivity and great potential of the PCR method for future research. Grant et al. [13] reported 100% sensitivity and 95% specificity of IMS-PCR using Dynabeads coated with polyclonal antibody. In comparison, Metzger-Boddien et al. [30] achieved 96% sensitivity using AnDiaTec ParaTub-S monoclonal antibody-mediated immunomagnetic separation PCR kit in combination with ELISA. This implies that IMS-PCR with Dynabeads is probably the best approach for detection of MAP in milk. Khare et al. [35] used a different type of bead with rabbit polyclonal anti-MAP antibodies, BioMag goat anti-rabbit IgG, with IS900 qPCR as an end-point detection method. This rapid technique allowed the detection of ten or fewer MAP cells in 2mL of milk, making this sensitive procedure very useful and cost-effective for the diagnosis of clinical and subclinical paratuberculosis. Recently, Gilardoni et al. [36] combined the use of IMS with monoclonal and polyclonal antibodies and modified IS900 (IS1 PCR) to detect MAP DNA. The aim of IS1 PCR is to amplify the IS1 fragment in the IS900 sequence. The IMS-IS1 PCR enabled a Limit of Detection of as low as 101CFU/mL of milk, when a 50:50 mix of monoclonal and polyclonal antibodies was used. This result is better than some of those listed in Table 1, but more investigation of this method is needed.

Dynabeads are the most commonly used beads in PMS studies (Table 1). MyOne Tosylactivated Dynabeads coated with the chemically synthesized MAP-specific biotinylated peptides aMp3 and aMptD were used by Foddai et al. [24]. They achieved 91.5% capture efficiency and minimal (<1%) nonspecific recovery of other Mycobacterium spp. In combination with a phage amplification assay. PMS was performed on 1mL milk samples using 5L biotinylated aMp3 peptide-coated beads and 5L biotinylated aMptD peptide-coated beads added separately to each reaction. This novel, rapid method for the detection and enumeration of viable MAP cells in milk was proven to be the best available magnetic separation approach, with results obtainable within 48h.

Subsequent evaluation of the other types of surface-activated paramagnetic beads showed that MyOne Tosylactivated Dynabeads coated with the S624 polyclonal antibody or peptides achieve a much higher capture efficiency for MAP than other surface-activated beads and that, generally, peptide-coated beads consistently achieve higher capture efficiencies than polyclonal-antibody-coated beads. On the other hand, the poorest capture efficiency was recorded for streptavidin-coated beads and amine-coated hollow glass beads, for which mean capture efficiencies were consistently found to be about 10% [24].

The aMptD peptide which binds to the MAP MptD protein was used separately but coupled directly (without a biotin-streptavidin bridge) to paramagnetic beads by carbodiimide in peptide-mediated capture ISMav2 PCR [33]. Experiments were based on a competitive capture assay where milk was spiked with MAP; the presence of an excess of other mycobacterial species demonstrated that only MAP had been captured. The results confirmed that the aMptD peptide is highly conserved among different MAP isolates. Independently of the MAP strain, 5 102MAP/mL could be reliably detected. Thus, this demonstrates the high specificity of aMptD and its suitability for use as a ligand in diagnostic tests.

Stratmann et al. [32] reproducibly detected MAP in bulk milk samples using MagneSphere streptavidin paramagnetic beads coated with either phage fMp3 or peptide aMp3 in combination with ISMav2 PCR. The Limit of Detection was found to be 102PFU/mL for fMp3 and 101PFU/mL for aMp3 peptide. As IS900 can exhibit nonspecific reactions, ISMav2, present in only three copies in the genome, was used. Foddai et al. [24] could detect as little as 0.3PFU/mL using Dynabeads, suggesting that it might be interesting to test Dynabeads in conjunction with ISMav2 in order to achieve even better results.

Regarding the methods for the isolation of MAP from feces, PMS with Dynabeads is the most commonly used method. However, in one case, IMS using BioMag goat anti-rabbit IgG with rabbit polyclonal anti-MAP antibodies was performed (Table 2).

In all reports bovine feces were used, and, thus, it remains unclear how the method would work for samples other than bovine feces. Frequently, a sample of feces (from 200mg to 1g) is diluted and only the suspension is subject to further analysis. Most often, the sample is diluted with water. Only in one case were undiluted feces taken [35, 37].

For the determination of sensitivity and/or LOD (Limit of Detection), artificially contaminated samples were used. Using the IMS method with BioMag goat anti-rabbit immunoglobulin G [IgG] and rabbit polyclonal anti-MAP antibodies, a LOD of 10 or fewer MAP organisms/200mg of feces was reached, whereas a sensitivity of 100% was achieved [35]. These results show that this procedure is very sensitive and cost-effective for the isolation and detection of MAP cells from feces. Nonetheless, to rigorously verify this method it will be necessary to test naturally contaminated samples, as well as samples of nonbovine origin.

The report of Swift et al. [39] is so far the only available description of the isolation of MAP from clinical blood samples using the PMS-phage method in order to achieve rapid detection of viable MAP (Table 3). To develop the method, 3.5 101PFU/mL of MAP were spiked into commercially available horse or sheep blood. In horse blood, no cells were detectable due to its high viscosity. In initial experiments on sheep blood, only 33% of the cells were recovered. Assuming that the blood was inhibiting the peptide binding or phage assay, samples were subsequently diluted. Samples were diluted 10x in modified 7H9 Media Plus and MyOne Tosylactivated Dynabeads coated with biotinylated peptides (5L aMp3, 5L aMptD) were used. The PMS-phage method combined with IS900 PCR was employed resulting in a Limit of Detection of 10 MAP cells/mL of sheeps blood. Moreover, when a 1 in 50 dilution (using modified 7H9 Media Plus) was used for sheep blood, 73% of MAP cells were recovered. However, a 1 in 10 dilution was set as the standard method as it resulted in 92% capture efficiency. These results proved that this assay is rapid and sensitive and can directly detect viable MAP cells present in naturally infected blood, all within 48h. However, optimization for blood samples from all susceptible animal species is needed.

It has been found that MAP is a bacterium with extraordinary temperature resistance, and in some cases, it can survive pasteurization of milk and the cheese-manufacturing process. These worrying properties have been verified using several techniques such as conventional cultivation or the plaque assay. However, only one publication reports the use of the MS method in this regard. In 2007, the IMS approach with an automatic Pathatrix magnetic capture system was used to detect MAP in raw bovine milk cheese samples (Table 4). Using several levels of MAP contamination, the LOD was determined to be 103 MAP/25g. Although no viable MAP cells were detected using conventional cultivation, the use of the F57-based real-time PCR system enabled the detection of MAP genetic elements [40].

In case of the MAP DNA detection, paramagnetic beads are not coated with MAP-specific ligands and they do not capture only MAP but also other mycobacterial DNA. Specificity is achieved by end-point PCR method.

As well as the detection of viable MAP cells, direct detection of MAP DNA is also employed. This approach is problematic due to the necessity of obtaining high purity DNA in sufficient amounts for PCR and is complicated by the presence of inhibitors in samples. In order to solve these problems, commercially available kits with DNA capture technology using paramagnetic beads and specific reagents that remove PCR inhibitors have been developed. The study of Donaghy et al. [41] assessed the performance of a commercially available MAP DNA extraction kit for milk, Adiapure, combined with the Adiavet PCR detection kit. Artificially contaminated raw milk with naturally MAP-infected feces (initial number of MAP cells 106107) was used to assess the sensitivity of MAP detection. The sensitivity of detection was found to be 90%, when 30 copies of IS900/mL (equivalent to approximately 2 cells) were detected (Table 5). For 300 copies of MAP, the sensitivity of detection reached 100%. This implies that the commercial Adiapure-Adiavet MAP DNA extraction and PCR detection kit allows consistent and sensitive detection of MAP in milk. In other studies, naturally contaminated milk was used. Herthnek et al. [42] tested the presence of MAP in bulk tank milk using the EZ1 DNA Tissue Kit with paramagnetic beads automatically processed in the BioRobot EZ1 workstation. The analytical sensitivity was assessed to be 100 MAP/mL for samples of 10mL (Table 5). Cultured environmental fecal samples (collected from the proximal environment of the cows) were used as a reference and 68% of the herds were positive, while 30% were positive by milk PCR. This result indicates that although MAP may be shed into milk, it will probably be present in low numbers in bulk tank milk due to dilution effects.

Leite et al. [14] compared six commercially available extraction kits for detection of MAP DNA using fecal samples from naturally infected cattle. Using the MagMAX Total Nucleic Acid Isolation Kit containing paramagnetic beads, 76% of the positive samples were identified using IS900 PCR (Table 6). Using the same extraction kit, 65% of MAP DNA samples were recovered in the study of Okwumabua et al. [43]. According to these results, and in comparison with other nonparamagnetic methods, MagMAX is considered to be a highly efficient method for the extraction of MAP DNA from fecal samples. The BioSprint 96 One-For-All Vet Kit was used by Plain et al. [44] for isolation of MAP from fecal samples from cattle and sheep and from sheep tissue samples. The Limit of Detection was calculated to be 102103 MAP/mL using artificially contaminated sheep fecal samples with initial concentrations of 106 to 101 MAP/mL.

Based on the number of the publications, the most intensively studied matrix using MS is milk. Almost no information is about the use of MS in blood, tissue, and cheese. In case of feces only one type of the origin of matrix was used. Regarding the composition, fecal matrix differs from one animal species to another; thus the access of MS will be also different (depending on the composition of the feed, consistency). There are no publications about the application of MS in infant milk formulas or another animal-derived foodstuff. In the 12th International Colloquium on Paratuberculosis (ICP) in Parma, Italy, there was only one piece of information about the use of MS in infant formulas (page 306; http://www.paratuberculosis.info/images/proc12/12icp.pdf). In the 13th ICP, there was one comparative study on PMS-phage assay with milk suppliers presented (page 48, P-03.10). This presentation highlighted the problem of unsuccessful transfer of the PMS-phage assay method between two different laboratories. Up to date, no publications based on these presentations were published. In addition, there is no investigated environmental matrix (environmental fecal samples from manure, scrapes, etc.). There is a big potential to make the screening of the farm easier with unknown history of paratuberculosis.

In case of all mentioned matrices (except for the tissue) the artificial contamination (AC) with MAP was used. This fact is crucial for the future evaluation. The AC could be used for the exact validation of the method for the selected matrix. Unfortunately, not a lot of publications include important data such as Limit of Detection, capture efficiency, and sensitivity. In general, no sufficient volume of the sample is used. In case of milk, only one milliliter does not have a big informative value and with regard to feces, 200mg is not sufficient as well.

Studies published in the last few decades show that the popularity of magnetic separation-based methods has rapidly increased, especially in connection with end-point PCR methods. This trend is due to the fact that MS-based methods are rapid, sensitive, and specific, selectively concentrate target bacteria into smaller volumes, and enable effective removal of PCR-inhibiting compounds. Appropriate sample preparation prior to PCR detection is crucial and for these purposes, new and more sensitive DNA isolation methods have been developed. Obtaining DNA of sufficient concentration and purity for subsequent applications, such as conventional or real-time PCR, represents the main challenges. Therefore, magnetic separation methods remain under development.

The studies discussed in this review document the detection of MAP in milk, feces, cheese, blood, and tissue. Two main approaches are used for the isolation of MAP cells from the above-mentioned matrices, IMS and PMS. For the detection of MAP cells in milk, M-280 sheep anti-rabbit immunomagnetic Dynabeads coated with polyclonal rabbit anti-MAP antibodies are the most commonly used type of beads for IMS. For the detection of MAP cells in feces, the best results are achieved when IMS is used, but PMS with peptide-coated MyOne Tosylactivated Dynabeads is the most commonly employed method at present. PMS in combination with the phage method has been used to determine the viability of MAP cells in blood; other magnetic separation methods have not been used in blood until now. Similarly as in blood, only one study using a magnetic separation method was conducted in cheese until now. Here, the IMS approach with automatic Pathatrix magnetic capture system was applied. For specific capture of MAP DNA, special commercially available kits with paramagnetic beads are used.

An interesting field where the magnetic separation methods were not used until now at all is infant formulas. This could be a field on which the following research should be focused especially when the reports on the presence of MAP in infant formulas appeared recently. In many cases, detection of MAP using magnetic separation methods has been carried out on artificially contaminated samples. For the development of reliable detection methods, more in-depth investigation and the use of naturally contaminated samples, especially of feces, tissues, and blood, is needed. The potential of the magnetic separation methods is broad. However, the main focus of the following research should be to improve the reliability of the assay for the use in many sectors of dairy and food industry.

The novel diagnostic assays for the detection of MAP discussed in this review are giving promising results. Thus far, the assays have not been validated according to OIE recommendations essential for their deployment in the control of animal infectious diseases as well as safeguarding the food chain. Validating the assays according to the OIE rules and testing their robustness in an interlaboratory study would help to harmonize and standardize the variety of assays, increase their acceptance, and facilitate their use in critical studies in animal disease control and food safety.

Copyright 2017 Marketa Husakova et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Related News
  1. megnatic separation
  2. manufacturer of magnetic separator for manganese processing 2 india
  3. inertial separator dust collector
  4. magnetic separator wikipedia
  5. spiral classifiers for mineral separation
  6. single screw spiral classifier for gold ore separation
  7. high quality hydro cyclone classifier separation machine for non ferrous minerals
  8. spiral chute separator adalah
  9. magnetic 0png
  10. what is the core meaning of magnetic separation
  11. small kaolin rock crusher in namibia
  12. mineral dressing machine wet magnetic separator
  13. magnetic separation meaning in tamil
  14. hydraulic cone crusher 80's toy
  15. power consumed by crushers and grinders
  16. crushing chemitry industrial
  17. sand washer in action
  18. materials for cone crusher
  19. high quality medium river sand high efficiency concentrator sell in glasgow
  20. namibia efficient stone cone crusher