Aspergillus fumigatus is a ubiquitous cosmopolitan fungus that may cause life-threatening complications in various immunocompromized patient populations. In order to discriminate between various isolates of different origin or to recognize isolates from a common origin, molecular typing methods offer the best available options. From the wide variety of molecular methods available, those that are highly reproducible and yield unambiguous, user independent, typing data should be preferred over other methods. Two such methods are Multi Locus Sequence Typing (MLST) and microsatellite analysis. Each of the two methods offer several advantages over the other. The main advantage of MLST is the DNA sequence format that is accessible to a growing number of clinical laboratories. DNA sequence data are easily compared and exchanged between labs. In addition, the same targets can potentially be used for isolates belonging to different species. On the downside are the relative high costs, turn-around time and the relatively low discriminatory power. This latter is a direct consequence of the relatively low mutation rate of a given DNA sequence due to the presence of mismatch repair mechanisms. Microsatellites are unique in their extremely high discriminatory power which is a direct result of the inherent instability, during DNA replication, of tandemly repeated DNA sequences. Fortunately, microsatellites are still sufficiently stable to allow longitudinal studies within an appropriate time window. However, interpretation of genotypically different isolates should be done with care and should take this instability into account. Microsatellites are amendable to rapid and high-throughput analyses in a modular fashion allowing large numbers of isolates to be analyzed in a timely fashion. The downside of microsatellite markers is that they usually are species specific. Basically, the choice for either of the two methods could be appropriate and should primarily be based on the exact reason for performing strain typing. MLST seems to be most informative at the genus and/or population level whereas microsatellites are best used when high-resolution strain typing is required.
Full conference title:
3rd Advances Against Aspergillosis
- AAA 3rd (2008)