Expert Insight: Management of bacterial and fungal infections: Efficiency of culture-independent molecular testing

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Dr. Michael Lustig, COO at Molzym GmbH & Co. KG

Conventional culture methods for the diagnosis of bacterial and fungal infections are often limited by a long time of culturing or the occurrence of negative results due to the administration of antibiotics or fastidious growth requirements. As an accepted alternative, culture-independent approaches are widely used. 

In this SelectScience^® webinar, Dr. Michael Lustig, COO at Molzym GmbH & Co. KG, shares his vast experience of direct molecular testing and presents a wide overview of available solutions and their applications. The factors that favor direct testing are outlined and the diagnostic value of broad-range 16S/18S rRNA gene PCR and how the results impact antimicrobial therapy selection is also discussed. 

Read on for the highlights of the live Q&A session or register to watch the webinar at a time that suits you.

Q: Can I also detect viruses with Molzym’s diagnostic solutions?

ML: We are not able to detect viruses yet as our technology is specific to the extraction and identification of microbes (bacteria & fungi) not viruses.

Q: If the flowing DNA is removed, including host, bacterial, or fungal DNA, how is the sensitivity maintained? 

ML: We remove the host DNA and the free-floating DNA from microbes which are already lysed beforehand. We then specifically enrich the remaining bacteria and fungi for extraction. We only look for bacteria and fungi which are still intact. The question concerning sensitivity is not easy to answer, as we can only analyze for analytic sensitivity. For example, in spiking experiments we can say (for the manual version) that we can go down to 20 colony-forming units (CFU) for bacteria and less than 10 CFU for fungi. However, for the clinical sensitivity it is quite different: here, we have added value which is 50-60% higher compared to the blood culture, so in these clinical samples we cannot count the bacterial load. 

Q: Are there any requirements for sample transport and storage? 

ML: Yes. The users should keep in mind that we run a DNAse step for the process of the human DNA depletion, so if they store the samples at -20 degrees or lower, then the bacteria might get lysed, and the free microbial DNA will also be degraded. The storage and transport conditions should be at 4 degrees or room temperature. The transport should be finished within 48 hours of the collection of the sample. 

Q: Can I use the enriched microbial DNA for other applications or assays? 

ML: Yes, with our process you get around 100 microlitres of high-purified microbial DNA from the bacteria and/or fungi. For our process, the 16S and 18S PCR, and the extraction control you need only 15 microlitres, so you have around 80 microliters left for any other analyses. This can be used for resistance gene testing or for next-generation sequencing (NGS) applications. 

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