Background:
The launched of MALDI microbial ID system in 2006 has revolutionized the way clinical diagnostic Microbiology laboratories operated by enabling Laboratory to rapidly identify Bacteria and now the common molds.
Lau A et al have offered a rigorous tube protein extraction method for fungus which does not only render the organism nonviable but it also allows the intracellular proteins to be freely available for analysis hence producing good-quality spectrum which lead to successful identifications obtained.
Sue S et al have also validated the MALDI-TOF for the identification of fungus focusing on the Australian demographics and were also successful with obtaining identification using the method outlined by Lau.
Both research groups concluded that the successful identifications of any fungus using MALDI-TOF MS is dependent on the fungal coverage in the existing database and to date this is insufficient unless complimented with an in-house database.
Summary:
Extraction method described by Lau A, Steven D et al have proven to be robust and feasible to adopt as part of Bacteriology routine workflow. Using this method, reliable and reproducible identification of Aspergillus fumigatus complex and Aspergillus niger complex was obtained.
Prospective studies (Lau A, Steven D et al & Sue S, Catriona H et al) have shown that reliable identifications to species level could be obtained from the primary RUO library when the cut-off score is lowered to ³1.70 to ³1.99 instead of the recommended ³2.00 by the manufacture.
The data obtained from our validation reflected this, as we were able to achieve 100% correlation with 30 isolates ( A. fumigatus and A.niger complex) when compared against phenotypic method.
At Royal Prince Alfred Hospital (RPAH), we have improved the utility of our existing Brucker MALD-TOF MS and TAT for the identification of A. fumigatus complex and A.niger complex without the added cost to the department’s current resources hence also improving patient care.