Implementation of MALDI-TOF Mass Spectrometry to Identify Fungi From the Indoor Environment as an Added Value to the Classical Morphology-Based Identification Tool

A comprehensive review of microbial contamination in the indoor environment: sources, sampling, health risks, and mitigation strategies

The quality of the indoor environment significantly impacts human health and productivity, especially given the amount of time individuals spend indoors globally. While chemical pollutants have been a focus of indoor air quality research, microbial contaminants also have a significant bearing on indoor air quality. This review provides a comprehensive overview of microbial contamination in built environments, covering sources, sampling strategies, and analysis methods. Microbial contamination has various origins, including human occupants, pets, and the outdoor environment. Sampling strategies for indoor microbial contamination include air, surface, and dust sampling, and various analysis methods are used to assess microbial diversity and complexity in indoor environments. The review also discusses the health risks associated with microbial contaminants, including bacteria, fungi, and viruses, and their products in indoor air, highlighting the need for evidence-based studies that can relate to specific health conditions. The importance of indoor air quality is emphasized from the perspective of the COVID-19 pandemic. A section of the review highlights the knowledge gap related to microbiological burden in indoor environments in developing countries, using India as a representative example. Finally, potential mitigation strategies to improve microbiological indoor air quality are briefly reviewed.

A comparative study for optimization of MALDI-TOF MS identification of filamentous fungi

PURPOSE

To evaluate and compare the performance of three commercial culture media, two filamentous fungi libraries, and two different protein extraction procedures in MALDI-TOF MS fungal identification.

METHODS

A total of 21 quality control samples were cultured on Sabouraud dextrose agar (SDA), ID fungi plate medium (IDFP), and Sabouraud gentamicin chloramphenicol 2 agar (SGC2). For four consecutive days, fungal growths were inoculated on a MALDI target plate both by using a direct transfer technique (DT) and by using a formic acid-ethanol protein extraction procedure (EEP). The MALDI-TOF MS-generated spectra were identified by the MBT Bruker library and the MSI database.

RESULTS

Selective culture media (IDFP and SGC2) significantly outperformed the non-selective SDA medium. IDFP was superior to the SGC2 medium for dermatophyte identification. The EEP only demonstrated a benefit over DT in the underperforming SDA medium. The MBT Bruker library outperformed the MSI database in Aspergillus identification while the MSI database outperformed the MBT library in dermatophyte identification. For non-Aspergillus fungi, the libraries performed comparably.

CONCLUSION

The results of our study show the necessity of using selective culture media (IDFP and SGC2) for fungal identification with MALDI-TOF MS and demonstrate no significant benefit of the formic acid-ethanol protein extraction technique in these media. Given the relative strengths and weaknesses of the MBT library and the MSI database, it might currently be beneficial to consider these libraries as complementary and employ both databases to achieve optimal fungal identification.

A Case of Invasive Fungal Infection Due to Scedosporium apiospermum in a Patient with Psoriasis

Scedosporium apiospermum (S. apiospermum) is typically reported to be involved in superficial and subcutaneous fungal infections but overlooked in invasive infections, which is associated with a high mortality rate. It poses a diagnostic challenge due to its confusable characteristics to other hyaline hyphomycetes. Here, we reported a psoriasis patient with an invasive S. apiospermum infection. The patient presents an abscess at the intermuscular space of the left hip and an increased C-reactive protein level. Pus culture showed white-greyish, cottonlike colonies with aerial mycelium and terminal oval conidia, suggesting S. apiospermum. This rare fungus was rapidly confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and RNA sequencing. The patient was successfully treated with voriconazole with no recurrence of the abscesses despite delayed treatment. This is the first such case infection report from China that described an unusual case of intermuscular space abscesses due to S. apiospermum. This report highlights the possibility of fungal infections in deeper tissue, as well as the necessity of thorough evaluation and microbiological diagnosis for invasive infections, particularly in immunocompromised patients.

Identification of Pathogenic and Opportunistic Yeasts in Pigeon Excreta by MALDI-TOF Mass Spectrometry and Their Prevalence in Chon Buri Province, Thailand

Pigeon excreta can cause environmental and public health issues, particularly in urban and public areas. They are reservoirs of several human pathogens including fungi, bacteria, and viruses. Epidemiological data of pathogenic and opportunistic yeasts in pigeon droppings in Chon Buri, one of the most reputable tourist cities of Thailand, are scarce. The present study aimed to identify yeasts in pigeon droppings by MALDI-TOF mass spectrometry, and to study their prevalence in Chon Buri, Thailand. A total of 200 pigeon fecal samples were collected randomly from all 11 districts of Chon Buri. A sum of 393 yeast-like colonies were isolated on Sabourand's dextrose agar and CHROMagar media. These isolates were further confirmed for their species by MALDI-TOF MS. Twenty-four yeast species belonging to 11 different genera were identified in pigeon fecal samples. Candida spp., predominantly C. krusei (14.32%), were the most prevalent yeast species. Other yeast species, including C. glabrata (12.73%), C. metapsilosis (11.93%), Lodderomyces elongisporus (10.87%), C. tropicalis (7.16%), C. albicans (5.83%), and Cryptococcus neoformans (4.77%) were identified. This study provides valuable epidemiological data and diversity of yeasts in pigeon droppings in Chon Buri, Thailand, and also supports the use of MALDI-TOF MS for yeast identification and epidemiological surveillance.