Clinical Data
Molzym's technology of human DNA removal from blood and other specimen, MolYsis, has been used for pathogen detection in several studies including clinical material. Below is a selection of data showing the performance of MolYsis in conjunction with in-house Real-Time PCR (RT-PCR) assays for the detection of bacteraemia or specific organisms.
| Study | 1 | 2 | 3 | 4 |
| Diagnosis | bacteraemia | bacteraemia | S. aureus / mecA | candidaemia |
Specimen (volume)
| whole blood
(1 ml)
| blood culture
(0.5 ml)
| whole blood
(1-5 ml)
| whole blood
(1-5 ml)
|
| Method | | | | |
DNA extraction
| MolYsis Complete5
| MolYsisPlus | MolYsis Complete5
| MolYsis Complete5
|
| Assay | 16S rDNA RT-PCR* + sequencing | Gram-differentiating RT-PCR* + group-specific RT-PCR* | S. aureus/ mecA-specific RT-PCR* | Candida-specific RT-PCR* |
No. samples
| 21 | 98 | 902 | 902
|
Sensitivity (%)
| 87.5 | 73.3 | 66.7
| 87.5 |
Specificity (%)
| 100 | 92.8 | 98.5
| 94.0 |
PPV (%)
| 100 | 64.7 | 38.1 | 20.0
|
NPV (%)
| 92.8 | 95.1
| 99.5 | 98.8
|
Positivity (%)
| | | | |
blood culture
| 42.8 | 15.3 | 1.3 | 1.1
|
| PCR | 33.3 | 17.3 | 2.3
| 3.8
|
| True septicaemia of PCR-positive, BC-negative patients (%) | | n = 6 | n = 10 | n = 28 |
| probablea | n.a. | 16.7
| 30.0
| 35.7
|
| possibleb | n.a.
| 16.7 | 70.0
| 64.3 |
| indeterminatec | n.a. | 66.6 | 0 | 0 |
| Reference | Handschur et al. (2008) | Gebert et al. (2008) | Wellinghausen et al. (2009a) | Wellinghausen et al. (2009b) |
a concordance to other microbiological data (e.g. swabs from wounds, drainage, secretions)
b other microbiological data not available, organisms detected are commonly found in blood cultures
c organisms detected are not usually found in blood culture
* RT-PCR, Real-Time PCR
Study 1 (Handschur et al., 2009)
In this study blood samples were extracted by the MolYsis Complete5 and subjected to a universal 16S rDNA PCR analysis, followed by sequencing of the amplification product and strain identification by FASTA analysis. The results were compared with those from blood cultures (BC). Both methods resulted in the detection of the same bacterial strains, except for one sample, being positive for S. epidermidis only in the BC. The authors conclude that the data of PCR were in good accordance with BC results, the discordant finding of S. epidermidis in BC most probably being the results of a contamination.
Reference:
Comp. Immunol. Microbiol. Inf. Dis. 32 (2009): 207-219
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Study 2 (Gebert et al., 2008)
Blood culture bottles were extracted by the MolYsis Plus kit and analysed by an in-house 16S rDNA-based Gram-differentiating Real-Time PCR assay, followed, if positive, by a Real-Time PCR algorithm differentiating among staphylococci, streptococci and enterococci as well as among Enterobacteriaceae and Pseudomonas aeruginosa. The results of the clinical parameters were calculated from the data in the paper. Samplings at different times after inoculation revealed that PCR results were obtained on average 10.7 h prior to signalling by the BACTEC system. The authors conclude that the approach may be a valuable supplemental tool for blood cultures in patients with suspicion of infection with slow-growing pathogens or serious clinical condition.
Reference: J. Inf. 57 (2008): 307-316
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Study 3 (Wellinghausen et al. 2009a)
A prospective study is reported aiming at the detection of Staphylococcus aureus bacteraemia and the presence of the mecA gene. Blood samples from critically ill patients were extracted using the MolYsis Complete5 kit and analysed by S. aureus and mecA-specific Real-Time PCR assays. Four of six patients positive for S. aureus by blood culturing were also positive in the PCR. The authors stress the point that blood culture results were obtained only by 13.5 h (mean) whereas PCR results were available already after 4 h enabling significantly earlier administration of pathogen-specific antimicrobial therapy. In 10 blood culture negative patients with other microbiological and clinical signs of infection a positive PCR result was noticed.
Reference: Eur. J. Clin. Microbiol. Infect. Dis. (in press)
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Study 4 (Wellinghausen et al. 2009b)
Rapid detection of candidaemia was the aim of this prospective study. For this purpose, blood samples were extracted by the MolYsis Complete5 Kit and analysed by an 18S rDNA-directed Real-Time PCR assay. In addition to the 7 PCR-positive cases of the 8 blood culture positive patients a positive PCR result was also obtained with 8 BC-negative patients with culture-confirmed Candida infection at primary sterile body sites. The authors conclude that the PCR approach allowed the detection of candidaemia at a mean of 3 days earlier than BC diagnostics thus enabling earlier antifungal therapy for patients.
Reference: J. Med. Microbiol. (in press): DOI 10.1099/jmm.0.007906-0
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Clinical Data