Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N1/00—Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
  • C12N1/06—Lysis of microorganisms
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/02—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving viable microorganisms
  • C12Q1/24—Methods of sampling, or inoculating or spreading a sample; Methods of physically isolating an intact microorganisms
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
  • C12Q1/6806—Preparing nucleic acids for analysis, e.g. for polymerase chain reaction [PCR] assay
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
  • C12Q1/6876—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes
  • C12Q1/6888—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms
  • C12Q1/689—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms for bacteria
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
  • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
  • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
  • C12Q1/6876—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes
  • C12Q1/6888—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms
  • C12Q1/6895—Nucleic acid products used in the analysis of nucleic acids, e.g. primers or probes for detection or identification of organisms for plants, fungi or algae
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M29/00—Means for introduction, extraction or recirculation of materials, e.g. pumps
  • C12M29/04—Filters; Permeable or porous membranes or plates, e.g. dialysis
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
  • C12M47/00—Means for after-treatment of the produced biomass or of the fermentation or metabolic products, e.g. storage of biomass
  • C12M47/06—Hydrolysis; Cell lysis; Extraction of intracellular or cell wall material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers

Definitions

• the present invention relates to the lysis of eukaryotic cells, in particular animal cells, such as blood cells.
• the present invention further relates to the detection of low concentrations of micro-organisms such as bacteria in samples with high concentrations of other cells.
• Molecular diagnostics aims at the rapid detection of minute amounts of pathogens (typically bacteria) in samples such as blood.
• Blood is however a complex matrix and comprises white blood cells (leukocytes) for the adaptive immune system, red blood cells (erythrocytes) for oxygen transport, and platelets (thrombocytes) for wound healing. This complicates the direct detection of pathogens in samples such as whole blood, which contain a high amount of cellular material.
• Classical detection methods comprise the growth of bacteria on selective media and/or media with indicators. Typically such assays require a cultivation step of at least 1 or 2 days before identification can take place.
• PCR based methods For PCR based methods the amount of bacteria in a fresh blood sample is theoretically high enough to be detected without further cultivation of the bacteria present within such sample.
• large volumes of blood are required.
• the high amount of DNA in especially white blood cells dramatically increases the background in DNA based detection methods.
• the presence of heme from hemoglobin strongly decreases the activity of DNA polymerase.
• a microliter of human blood contains about 4,000 to 11,000 white blood cells and about 150,000 to 400,000 platelets.
• the concentration of DNA in blood is between 30 and 60 ⁇ g/ml. It is extremely challenging to detect in a volume of 10 ml of whole blood the presence of about 10 to 100,000 of a bacterial species.
• the high amounts of DNA of the white blood cells may give rise to non relevant PCR products, or may scavenge the primers designed for the detection of bacterial DNA. This necessitates a thorough DNA purification and separation of mammalian DNA before the bacterial DNA can be detected via PCR or other methods.
• DNA increases the viscosity of a sample.
• proteins and membranes from the lysed mammalian cells form complexes which prevent the filtration of a sample. This is particularly a problem for miniaturized devices. Further dilution of the, already large sample volume, results in unacceptable long manipulation steps.
• LooxterTM from the company SIRSLab uses a method to enrich methylated DNA
• One aspect of the invention relates to a method for the selective lysis of eukaryotic cells, in particular animal cells, within a sample containing or suspected to contain a micro-organism.
• This method comprises the steps of providing a sample with eukaryotic cells, in particular animal cells, containing or suspected to contain a micro-organism, adding a non-ionic detergent and a buffer to the sample to obtain a solution with a pH of about 9,5 or more, and incubating the solution for a time period sufficiently long to lyse the eukaryotic cells, in particular animal cells, for example between 30 seconds and 10 minutes, more preferably between 2 and 6 minutes.
• the lysis can be performed in particular embodiments between 15 and 30 °C, more preferably around room temperature.
• the sample is a mammalian blood sample, such as whole blood.
• the micro-organism is a bacterium or fungus.
• the ratio between the volume of added detergent and added buffer and the volume of sample is between 2/1 and 1/10.
• the non- ionic detergent is selected from the group comprising Nonidet, Brij, Tween, Igepal, reduced triton, octylglucoside, cholaat and Triton. More preferred examples are Triton X-100, Nonidet P40, Sodium deoxycholate and or Igepal CA 630.
• the alkaline buffer as used herein has a pKa value above 9.
• Examples hereof are borate, carbonate, CAPS (N-cyclohexyl-3- aminopropanesulfonic), CAPSO (3-(Cyclohexylamino)-2-hydroxy-l- propanesulfonic acid), CHES (2-(N-Cyclohexylamino)ethane Sulfonic acid), pyrophosphate and ethanolamine.
• a particular example is sodium carbonate.
• the buffer should have sufficient buffer capacity that when mixed with the sample in ratios according to the present invention, the pH of the final solution is around 9.5 or higher.
• the method further comprises the step of filtering the incubated solution on a filter with a pore size which retains micro-organisms on the filter, such as a filter with a pore size of less than 0.7 ⁇ , more preferably less than 0.5 ⁇ .
• the method of the present invention facilitates the filtration of high volumes of sample without enzymatic or heat related process steps.
• the method further comprises the step of adding after the selective lysis according to the invention an acid or acidic buffer to obtain a pH between about 7 and 9, a " neutralization step".
• the methods as described above are followed by detection of the micro-organisms.
• Examples hereof are cytometry, microscopy, PCR or culturing.
• a device (1) for the detection of micro-organisms in sample comprising: a lysis chamber (2) for accepting a sample fluid with a volume below 40 ml, preferably below 20 ml and more preferably between 1 and 20 ml, a reservoir (3) comprising an alkaline buffer with a pH of about 9,5 or more and comprising a non- ionic detergent, or a reservoir comprising an alkaline buffer (31) with a pH of about 9,5 or more, a reservoir comprising a non-ionic detergent (32), connected to the lysis chamber, a filter (4) connected to the lysis chamber for filtering the sample after lysis, the filter having a pore size which retains bacteria on the filter, and a detection chamber (5) for assaying the presence of DNA.
• the alkaline buffer has typically a pKa above 9,5 so the final solution will have a pH of about 9.5 or higher, and the non- ionic detergent is typically Triton X-100, Sodium deoxycholate, Nonidet P40 and/or Igepal CA 630.
• Methods as described in the present invention allow a selective lysis of white and red blood cells in a sample while bacteria and fungi remain intact (either dead or alive).
• Methods as described in the present invention make it possible to process a sample without substantially diluting such sample, and consequently allow to process larger volumes of sample.
• Methods as described in the present invention result in lysed samples with a low viscosity and a minimum of aggregates, which makes it possible to filter large volumes of the lysed sample over a filter which retains bacteria. Further processing of the bacteria on such filter can proceed with volumes between about 100-1000 ⁇ , which makes it possible to process large sample volumes for subsequent procedures and to perform the required manipulations, such as neutralization and washing, fully automated in an integrated cartridge.
• Fig. 1 shows the filtration efficiency of large volumes of blood after selective lysis at different pH values in accordance with a particular embodiment of methods of the invention.
• Fig. 2 shows the recovery of different bacteria after lysis at different pH values in accordance with a particular embodiment of methods of the invention.
• Fig. 3 shows the recovery of different bacteria after lysis at different incubation times in accordance with a particular embodiment of methods of the invention.
• Fig. 4 shows reduction of human background DNA by selective lysis according to the present invention.
• Fig. 5 and 6 show detection of different types of pathogens in 1 and 5 ml full blood respectively.
• Fig. 7 shows a comparison between manual and device performed method according to the present invention.
• Fig. 8 shows comparison of the method according to the invention to commercially available sepsis detection test
• Fig. 9 shows lysis of pathogens after selective lysis and capture on filter according to the present invention.
• Fig. 10 shows pathogen lysis efficiency in comparison to other lysis methods when performed after selective lysis and capture on filter according to the present invention.
• Fig. 11 shows a schematic overview of an embodiment of a device for performing a selective lysis as described in embodiments of the present invention.
• Fig. 12 shows an example of an integrated device comprising a selective lysis unit as described in embodiments of the present invention
• Blood cells in the context of the present invention relates to mammalian cells present in blood and includes red blood cells (erythrocytes), white blood cells
• leukocytes and blood platelets (thrombocytes).
• Whole blood in the context of the present invention relates to unprocessed blood comprising blood plasma and cells, potentially treated with an anti-coagulant.
• Sample relates to an aqueous suspension comprising cellular material and comprises body fluids such as lymph, cerebrospinal fluid, blood (whole blood and plasma), saliva, but also comprises e.g. the aqueous fraction of homogenized suspensions such as e.g. muscles, brain, liver, or other tissues.
• Eukaryotic in the present invention relates to any type of eukaryotic organism excluding fungi, such as animals, in particular animals containing blood, and comprises invertebrate animals such as crustaceans and vertebrates.
• Vertebrates comprise both cold-blooded (fish, reptiles, amphibians) and warm blooded animal (birds and mammals).
• Mammals comprise in particular primates and more particularly humans.
• “Selective lysis” as used in the present invention is obtained when in a sample (such as blood) the percentage of micro-organism cells (such as bacterial cells) in that sample that remain intact is significantly higher (e.g. 2, 5, 10, 20, 50, 100, 250, 500, or 1000 time more) compared to the percentage of the eukaryotic cells from the organism from which the sample is collected that remain intact.
• Micro-organism as used in the present invention relates to bacteria (gram positive and gram negative bacteria, as well as bacterial spores) and unicellular fungi such as yeast and molds, which are present in the organism from which a sample has been collected, typically as a pathogen.
• a first aspect of the present invention relates to a method for the selective lysis of eukaryotic cells, in particular animal cells, within a sample, which contains or is suspected to contain micro-organisms such as bacteria.
• the aim of the method is to increase the sensitivity of a test for the detection of minute amounts of bacteria in a sample (i.e. less than 10000, 1000, 100 or even less micro-organisms per ml of sample).
• DNA from eukaryotic cells, in particular from animal cells, in a sample interferes with PCR based detection methods and this DNA, together with proteins and membranes form aggregates which increases viscosity after lysis and which has a dramatic impact on the filtration of a lysed sample.
• the eukaryotic cells in particular animal cells, are selectively lysed whereby a substantial part (i.e. more than 20 %, 40%, 60%, 80%>, 90%> or even more that 95%>) of the micro-organisms remains alive, or if killed by the treatment, still comprise the bacterial DNA within the cell wall.
• a substantial part i.e. more than 20 %, 40%, 60%, 80%>, 90%> or even more that 95%>
• Methods as described in the present invention are particularly applicable to any type of sample wherein the detection of DNA from micro-organisms, particularly from bacteria, is impaired by the presence of other cells comprising DNA, in particular cells from a host wherein the micro-organism is present as a pathogen.
• the blood sample can be stored as whole blood or a processed fraction such as plasma or a platelet preparation. Typically, methods as described in the present invention are performed on freshly isolated whole blood. Such samples are generally treated with e.g. heparin, EDTA or citrate to avoid coagulation.
• the method is performed on fresh blood by collecting the blood from the vein directly in a tube with detergent and buffer.
• a fresh blood sample or a preserved sample is supplemented with a buffer and a non- ionic detergent.
• the selection of the buffer and its concentration are chosen in order to compensate the buffering capacity of the blood sample provided and to obtain a pH around or higher than 9,5, more particular between 9,5 and 11,5, even more particular between 9,5 and 10,5. pH values above 11,5 are suitable for more robust organisms such as gram positive bacteria and fungi.
• Equally the buffer is sufficiently concentrated such that at most a buffer volume of 200%, 150%, 100%, 50%, 20 % or 10 % of the sample volume is added to the sample to obtain the required change in pH.
• Suitable buffers in the context of the present invention typically have a pKa above 9, above 9,5 or even above 10 and include borate, carbonate, CAPS, CAPSO, CHES, pyrophosphate, ethanolamine, and other commonly used buffers with an optimal buffering capacity in the above mentioned pH ranges
• Suitable detergents are non-ionic detergents, which at the one hand have a lytic effect on the eukaryotic cells, in particular animal cells, only and on the other hand have a solubilising effect on DNA and proteins.
• non- ionic detergents examples include alkylglycosides, Brij 35 (C12E23 Polyoxyethyleneglycol dodecyl ether) (15,7), Brij 58 (C16E20 Polyoxyethyleneglycol dodecyl ether) (16), Genapol (13 to 19), glucanids such as MEGA-8, -9, -10, octylglucoside (12,6), Pluronic F127, Triton X-100 (Ci 4 H220(C2H 4 0) n ) (13,4), Triton X-l 14 (C 24 H 42 0 6 ) (12,4), Tween 20 (Polysorbate 20) (16, 7) and Tween 80 (Polysorbate 80) (15) Nonidet P40 sodium deoxycholate, reduced Triton X-100 and or Igepal CA 630.
• a particular preferred example of a non- ionic detergent is Triton-X 100.
• the most effective concentration of detergent depends from detergent to detergent, but typically is within the range of between 0,1 and 5 %, more particularly between 0,1 and 1 %.
• % refers to respectively w/v % or v/v %.
• the incubation of a blood sample in the presence of buffer and detergent is performed within 10 minutes, preferably between 30 seconds and 10 minutes and more preferably between about 1 to 3, 1-5, 1-8, 2-6 or 1-10 minutes, at temperatures between 10 and 30 °C, more preferably around room temperature.
• Methods according to the present invention have the advantage that a selective lysis is obtained below 10 minutes, at temperatures below 30 °C. Accordingly, the methods can be generally performed at ambient temperatures without the need to heat the sample.
• the pH of the lysed sample is brought to a neutral value (i.e. between 7 and 9) by the addition of an acid or acidic buffer in a neutralization step. It was found that a lysed sample at neutral pH could be stored for a prolonged time (up to 1 , 2, 6, 12 or even 24 hours) without further lysis of bacterial cells and without dramatic changes in the fluidic properties of the lysed sample.
• Another parameter investigated in the methods of the present invention is the evaluation of the fluidic properties of the blood sample after lysis . This can be determined by verifying which volume of lysed blood can be filtered through a 0.22 ⁇ filter. Methods in accordance with the present invention allow the filtration of at least 2, 5, 7,5 or even 10 ml of whole blood which was diluted by addition of 1 volumes of buffer/detergent solution to 1 volume of sample.
• methods in accordance with the present invention comprise a step wherein the intact bacterial cells are separated from the sample, typically performed by centrifugation or filtration.
• intact bacteria are separated from the sample by passage of the lysed sample over a filter, with a pore size below 1 ⁇ , to retain bacteria which have typically a size between 0.5 and 10 ⁇ , such as commercially available filters with a pore size of 0.4 or 0.22 ⁇ .
• filters adapted to fit on a syringe such that after lysis within in syringe, the fluid can be passed over the filter by manual pressure on the plunger of the syringe.
• bacteria or fungi
• the presence of micro-organisms is investigated by PCR.
• bacteria (or fungi) can be washed away from the filter and further treated for PCR amplification.
• the filter is rinsed with a lysis buffer to release the DNA from the micro-organisms, which is further used in a PCR reaction.
• a device (1) comprising a lysis chamber (2) for accepting a sample fluid with a volume between 1 and 10 ml, a reservoir (3) comprising an alkaline buffer with surfactants as described above, or a reservoir comprising an alkaline buffer (31) as described above and a reservoir comprising surfactants (32) as described above, the reservoirs connected to the lysis chamber (2).
• the lysis chamber is connected to a filter (4) for filtering the sample after lysis whereby micro-organisms are retained on the filter.
• the device further comprises channels to remove the micro-organisms from the filter and lyse them in a separate chamber.
• the device further comprises means for lysing micro-organisms on the filter, and channels to transfer DNA from lysed bacterial or fungal cells from the filter to a separate chamber.
• the device can further contain a DNA purification and detection chamber (5) for assaying the presence of DNA.
• the detection chamber is a PCR module.
• the goal of this experiment is to assess the effect of pH of the buffer on filtration efficiency.
• the buffer capacity was sufficient to obtain a similar pH in the final solution as confirmed by measuring the pH of the final solution using conventional techniques known to the person skilled in the art.
• Identical amounts of bacteria are spiked into 1 ml blood. This volume is treated with the above-mentioned buffers for 3 min. Hereafter the blood is centrifuged (10 min, 4000g) to collect the intact bacteria. Bacteria are lysed using a standard alkaline lysis method and the DNA is purified using Qiagen spin columns (QiaAmp blood mini kit). The amount of DNA is quantified using real-time PCR. The result is shown in Figure 2.
• the abovementioned figure shows the recovery of the bacteria as a function of the pH of the selective lysis buffer.
• the white blood cell DNA is not degraded and is inhibiting the PCR reaction.
• the bacteria start to be lysed during the selective lysis and they are not recovered.
• This example demonstrates the influence of prolonged incubation of blood with the selective lysis buffer according to the invention on the recovery of intact pathogens.
• a fixed number of P. aeruginosa bacteria was spiked into blood. 1 ml of spiked blood was mixed with 1 ml selective lysis buffer (1 M NaCarbonate pH 10.0 + 1 % Triton X-100) and incubated for 1,2,3,5,7 or 10 minutes. Hereafter, 1 ml of neutralization buffer was added. The pathogens were collected by centrifugation (10 min at 4000 g) and the bacterial pellet was washed. Finally, the cells were lysed by standard alkaline lysis followed by DNA
• Reduction of human background by selective lysis according to the present invention Reduction of the amount of eukarytotic cell DNA, more specifically white blood cell DNA in the current method is important since when present, it will inhibit a following PCR reaction to detect pathogen DNA or RNA.
• different blood samples are processed with the selective lysis protocol according to the present invention and the amount of white blood cell DNA in the PCR reaction is analyzed using the RNaseP detection kit (Applied Bio systems). The Ct values of these samples are compared with those obtained from 200 ⁇ blood full blood samples, where all white blood cell DNA was present. From literature it is known that the human DNA originating from 200 ⁇ full blood is the maximum amount of background DNA that can be tolerated by a PCR reaction without inhibition of the pathogen DNA
• This figure shows the difference in amount of human background between the 1 ml processed blood samples according to the method of the present invention ((1 M
• the goal of this example is to demonstrate the detection of the different types of pathogens from full blood by using the method according to the present invention.
• the different types of pathogens a gram-negative (P. aeruginosa), gram-positive (S. aureus) and fungi (C. albicans) were mixed together into 1 ml blood.
• the blood sample was treated with the selective lysis buffer (1 ml of a 1M NaCarbonate pH 10.0 + 1% TX-100 solution) for 3 min followed by neutralization of the pH and filtration using a size selection filter with sufficiently small pores to retain all cells.
• the filter was washed to remove the remaining inhibitors such as hemoglobin and DNA of the white blood cells.
• the cells were lysed following a standard alkaline lysis protocol and the DNA was purified using the Qiagen blood mini kit.
• the pathogenic DNA was detected by real-time PCR; the Ct value is a measure for the amount of DNA.
• Ct value is a measure for the amount of DNA.
• For quantification a small part of the spiked blood sample was plated on blood agar plate to obtain the CFU count.
• the data as present in figure 5 show that it is possible to detect low numbers of pathogens from full blood.
• the reference sample contains the same number of bacteria in a small volume of PBS buffer which is directly lysed, followed by DNA purification and quantification using real time PCR.
• the reference measurements and the actual enrichment experiments from blood gave similar Ct values, thus demonstrating the hiqh recovery rates.
• the negative control blood without bacteria shows no PCR signal.
• the assay allows larger volumes of blood to be used.
• the experimental set-up is identical to the previous example but the amount of blood is increased to 5 ml.
• the reference sample contains the same number of pathogens as the 5 ml blood sample but the cells remain in a small volume of PBS and are directly lysed. The results are represented in Fig. 6.
• the selective lysis method according to the present invention may be performed in various ways, not limited to but including a manual procedure and a procedure wherein the method is performed by a device according to the present invention (integrated procedure).
• integrated procedure The present example compares such an integrated procedure and a manual procedure.
• the manual procedure requires manual pipetting and centrifugation steps while the integrated procedure uses a micro-fluidic cartridge and a size selection filter, capable of performing all the required operations.
• the basic biochemical protocol is similar: selective lysis of the white and red blood cells using a 1M NaCarbonate + 1% Triton X-100 solution followed by a neutralization step after 3 min.
• the method according to the present invention is benchmarked against a commercially available method namely the MolYsis Complete kit (Molzym).
• This kit uses chaotropic agents and detergents to lyse selectively mammalian cells. This lysis step is followed by a digest with a DNAse which is not affected by this chaotropic
• the Ct values are plotted against the concentration of cells in figure 8 and show that the method according to the present invention is at least as efficient as the known MolYsis kit without the addition of enzymes or chaotroptic salts.
• alkaline lysis was employed to achieve simultaneous lysis of different pathogens on the filter to make the DNA available for PCR analysis.
• Figure 9 shows the result of the alkaline lysis procedure performed on an integrated cartridge.
• 1 ml of blood was spiked with 10 6 cells of S. aureus, P. aeruginosa and C. albicans.
• alkaline lysis was performed, using 200 ⁇ of a solution containing 200 mM NaOH, 0.5% SDS which is incubated at 95°C for 10 min to obtain complete lysis of the pathogens in the filter.
• the eluates containing the pathogen DNA were neutralized with 20 ⁇ of a 1 M citric acid solution and purified using the QIAamp DNA/Blood Mini kit.
• 10 6 cells of each pathogen were lysed on the bench, neutralized and purified as described above.
• FIG. 10 compares the alkaline lysis procedure (using 50 mM NaOH, 0.25% SDS in combination with heat treatment) with other lysis methods, namely high intensity ultrasound (HiFU) treatment and a commercial kit (BD GeneOhm lysis kit).
• HiFU high intensity ultrasound
• BD GeneOhm lysis kit BD GeneOhm lysis kit
• PCR reaction was conducted in Taqman Universal mastermix (Applied Biosystems), using 500 nM forward primer and 300 nM reverse primer and FAM-BHQ1 labelled probe (all oligonucleotides custom synthesized by Biolegio BV). The PCR reaction was performed in a Biorad CFX real-time PCR system.

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  • 2010-12-07 JP JP2012542666A patent/JP5937013B2/ja active Active
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