Comparison of molecular and MALDI-TOF MS identification and antifungal susceptibility of clinical Fusarium isolates in Southern China

Formic acid sandwich method is well-suited for filamentous fungi identification and improves turn around time using Zybio EXS2600 mass spectrometry

OBJECTIVES

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is extensively employed for the identification of filamentous fungi on MALDI Biotyper (Bruker Daltonics) and Vitek MS (biomerieux), but the performance of fungi identification on new EXS2600 (Zybio) is still unknow. Our study aims to evaluate the new EXS2600 system's (Zybio) ability to rapidly identify filamentous fungi and determine its effect on turnaround time (TAT) in our laboratory.

METHODS

We tested 117 filamentous fungi using two pretreatment methods: the formic acid sandwich (FA-sandwich) and a commercial mold extraction kit (MEK, Zybio). All isolates were confirmed via sequence analysis. Laboratory data were extracted from our laboratory information system over two 9-month periods: pre-EXS (April to December 2022) and post-EXS (April to December 2023), respectively.

RESULTS

The total correct identification (at the species, genus, or complex/group level) rate of fungi was high, FA-sandwich (95.73%, 112/117), followed by MEK (94.02%, 110/117). Excluding 6 isolates not in the database, species-level identification accuracy was 92.79% (103/111) for FA-sandwich and 91.89% (102/111) for MEK; genus-level accuracy was 97.29% (108/111) and 96.39% (107/111), respectively. Both methods attained a 100% correct identification rate for Aspergillus, Lichtheimia, Rhizopus Mucor and Talaromyces species, and were able to differentiate between Fusarium verticillioides and Fusarium proliferatum within the Fusarium fujikuroi species complex. Notably, high confidence was observed in the species-level identification of uncommon fungi such as Trichothecium roseum and Geotrichum candidum. The TAT for all positive cultures decreased from pre EXS2600 to post (108.379 VS 102.438, P < 0.05), and the TAT for tissue decreased most (451.538 VS 222.304, P < 0.001).

CONCLUSIONS

The FA-sandwich method is more efficient and accurate for identifying filamentous fungi with EXS2600 than the MEK. Our study firstly evaluated the performance of fungi identification on EXS2600 and showed it is suitable for clinical microbiology laboratories use.

Extensive primary cutaneous fusariosis in a patient with burns: A case report and review of the literature

BACKGROUND

Fusarium species can cause a broad spectrum of human infections, ranging from superficial and locally invasive to disseminated, depending on the immune status of the host and portal of entry. Although several cases of cutaneous fusariosis in burn victims have been reported, molecular identification for pathogen recognition has been used only in a few cases.

CASE DESCRIPTION

In this report, we describe an uncommon case of extensive primary cutaneous fusariosis caused by Fusarium keratoplasticum in a patient who sustained injuries during stubble burning.

FINDINGS

A review of cases of cutaneous fusariosis in burn victims revealed that this uncommon infection could be lethal, and treatment strategies should focus on both surgical debridement and the initiation of systemic antifungal therapy. Furthermore, because skin defects can serve as a portal of entry for Fusarium species in burn victims, early and aggressive treatment is crucial to prevent serious consequences.