Electrochemical detection of bacterial and/or fungal infections
The present disclosure relates to methods and devices for amplifying a plurality of targets in a single PCR run while distinguishing between clinically relevant amplification and amplification from other sources such as from background contamination. The methods and devices further enable discrimination between gram-positive, gram-negative and fungal infections as wells as identify antimicrobial resistance genes. When applying the methods and devices of the invention, the species or genus of an infection(s), and genus of a fungal co-infection(s) or category of bacterial (gram-positive or negative) co-infection(s) are identified. Species identification of co-infections can also be achieved. Further, when applying the methods and devices of the invention, organisms which are likely to be contaminating organisms from a blood draw are identified.
1. An in vitro method for detecting a viable gram-positive microorganism comprising:
a) subjecting a sample in blood culture medium, i) the sample comprising or suspected of comprising, the viable pram-positive microorganism and ii) the blood culture medium comprising nucleic acid from a non-viable gram-positive microorganism, wherein the non-viable cram-positive microorganism is the same pram-positive microorganism as the viable gram-positive microorganism, and is present in the sample at a lower concentration than the viable gram-positive microorganism, to a single detuned multiplex end-point polymerase chain reaction (PCR) to produce amplicons, the PCR comprising about 30 to about 35 cycles;
b) contacting amplicons from step a with a plurality of signal probes and a plurality of capture probes, one of the signal probes and one of the capture probes is specific for the amplicons to form a hybridization complex; and
c) electrochemically detecting an amount of hybridization complex above a threshold thereby detecting the viable gram-positive microorganism, and not detecting the nucleic acid from the non-viable gram-positive microorganism present in the blood culture medium.
2. The method of claim 1 , further comprising, prior to step a, contacting the sample with a compound which hydrolyzes nucleic acids and extracting the nucleic acids.
3. The method of claim 1 , wherein if four or more microorganisms are detected by the method, the method is repeated.
4. The method of claim 1 , further comprising generating an epidemiology report on a clinical instrument.
5. The method of claim 1 , further comprising reporting the detected viable gram-positive microorganism to a hospital's laboratory information system (LIS).
6. The method of claim 1 , wherein the viable gram-positive microorganism is a Bacillus cereus , a Micrococcus , a Bacillus subtilis , a Staphylococcus , a Staphylococcus aureus , a Propionibacterium acnes , a Staphylococcus epidermidis , a Staphylococcus lugdunensis , a Enterococcus faecalis , a Streptococcus , a Enterococcus faecium , a Streptococcus agalactiae , a Lactobacillus , a Listeria , a Streptococcus pneumoniae , a Listeria monocytogenes , or a Streptococcus pyogenes.
7. The method of claim 1 , wherein the viable gram-positive microorganism is a S. anginosus , a Enterococcus spp., or a Corynebacterium and the single detuned multiplex end-point PCR comprises primers at a primer concentration of about 250 nM.
8. The method of claim 1 , wherein the single multiplex PCR comprises shuttling, by electrowetting manipulation, the sample across thermal zones comprising a denature heater and an anneal/extension heater.
9. The method of claim 1 , wherein a Streptococcus spp., a P. acnes and a Streptococcus pneumoniae gram-positive microorganism are amplified together in a multiplex pool.
10. The method of claim 1 , further comprising detecting a viable gram-negative microorganism, fungal microorganism or antimicrobial resistance gene.
11. The method of claim 1 , wherein false positives from the non-viable microorganism is less than 5%.
12. The method of claim 1 , wherein the method has a limit of detection of 1×10 5 CFU/mL, 1×10 4 CFU/mL, or 1×10 6 CFU/mL.
13. An in vitro method for detecting a viable gram-negative microorganism comprising:
a) subjecting a sample in blood culture medium, i) the sample comprising or suspected of comprising, the viable gram-negative microorganism and ii) the blood culture medium comprising nucleic acid from a non-viable gram-negative microorganism, the non-viable gram-negative microorganism is the same gram-negative microorganism as the viable gram-negative microorganism, and is present in the sample at a lower concentration than the viable gram-negative microorganism, to a single detuned multiplex end-point polymerase chain reaction (PCR) comprising about 30 cycles to produce amplicons;
b) contacting amplicons from step a with a plurality of signal probes and a plurality of capture probes, one of the signal probes and one of the capture probes is specific for the amplicons to form a hybridization complex; and
c) electrochemically detecting an amount of hybridization complex above a threshold thereby detecting the viable gram-negative microorganism, and not detecting the nucleic acid from the non-viable gram-negative microorganism present in the blood culture medium.
14. The method of claim 13 , wherein the viable gram-negative microorganism is a Acinetobacter baumannii , a Klebsiella pneumoniae , a Bacteroides fragilis , a Morganella morganii , a Citrobacter , a Neisseria meningitides , a Cronobacter sakazakii , a Proteus , a Enterobacter cloacae complex, a Proteus mirabilis , a Enterobacter , a Pseudomonas aeruginosa , a Escherichia coli , a Salmonella , a Fusobacterium necrophorum , a Serratia , a Fusobacterium nucleatum , a Serratia marcescens , a Haemophilus influenza, a Stenotrophomonas maltophilia , or a Klebsiella oxytoca.
15. The method of claim 13 , further comprising detecting a viable gram-positive microorganism, fungal microorganism or antimicrobial resistance gene.
16. An in vitro method for detecting a viable fungal microorganism comprising:
a) subjecting a sample in blood culture medium, i) the sample comprising or suspected of comprising, the viable fungal microorganism and ii) the blood culture medium comprising nucleic acid from a non-viable fungal microorganism, the non-viable fungal microorganism is the same fungal microorganism as the viable fungal microorganism, and is present in the sample at a lower concentration than the viable fungal microorganism, to a single detuned multiplex end-point polymerase chain reaction (PCR) to produce amplicons wherein the PCR comprises multiple pairs of primers and at least one pair of primers comprises mismatches compared to a gene of the viable fungal microorganism;
b) contacting amplicons from step a with a plurality of signal probes and a plurality of capture probes, one of the signal probes and one of the capture probes is specific for the amplicons to form a hybridization complex; and
c) electrochemically detecting an amount of hybridization complex above a threshold thereby detecting the viable fungal microorganism, and not detecting the nucleic acid from the non-viable fungal microorganism present in the blood culture medium.
17. The method of claim 16 , wherein the viable fungal microorganism is a Candida albicans , a Candida lusitaniae , a Candida auris , a Candida dubliniensis , a Candida famata , a Cryptococcus gattii , a Candida glabrata , a Cryptococcus neoformans , a Candida guilliermondii , a Fusarium , a Candida kefyr , a Malassezia furfur , or a Candida krusei.
18. The method of claim 16 , wherein the hybridization complex comprising a Candida parapsilosis or a Candida tropicalis fungal microorganism is detected in two detection zones.
19. The method of claim 16 , wherein the viable fungal microorganism is a Rhodotorula or a Trichosporon and the primers for the Rhodotorula or the Trichosporon viable fungal microorganism contain mismatches compared to a wildtype gene for Rhodotorula or Trichosporon.
20. The method of claim 16 , wherein the single detuned multiplex end-point PCR comprises primers consisting of the nucleic acid sequence of SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, or SEQ ID NO: 9.