Environmental characteristics and taxonomy of microscopic fungi isolated from washing machines

Study on microbial diversity of washing machines

Health and environmental protection are the development trend of household appliances, coupled with the impact of the COVID-19 epidemic in the past few years. Consumers have unprecedented concerns and expectations about the sterilization and disinfection functions of household appliances. As a washing and nursing equipment for household clothes, the anti-bacterial technology of washing machine has developed rapidly. The new models of washing machines in the market have basically added the function of sterilization. In order to thoroughly solve the problem of sterilization and bacteriostasis of washing machines from the source, the distribution of microbial contamination in washing machines should be fully investigated. At present, there is almost no systematic study on the microbial community structure in washing machines in China. Therefore, the purpose of this study is to analyze the bacterial community structure in Chinese household washing machines. To explore the key factors affecting the bacterial community structure of washing machines. Bacterial communities were comprehensively analyzed by high throughput sequencing. Using chao and shannon indexes as indicators, one-way ANOVA was used to explore the key factors affecting the bacterial community structure of washing machines. A total of 2,882,778 tags and 21,265 OTUs from 522 genera were sequenced from 56 washing machine samples. Genus Mycobacterium, Pseudomonas, Brevundimonas, Sphingomonas, Sphingobium, Enhydrobacter, Methylobacterium, Pseudoxanthomonas, Stenotrophomonas and Sphingopyxis were the top ten bacteria genera in abundance. The effects of sources, types, frequency of utilization, sampling locations and service life of washing machines on bacterial diversity in washing machine were systematically analyzed. The statistical analysis showed that service life was an important factor affecting bacterial diversity in washing machine. Our study lays a foundation for directional screening of characteristic microorganisms with targeted characters including malodor-producing, fouling, pathogenic and stress-resistance, the antibacterial evaluation, metabolic mechanism of key characteristic microorganisms as well as antibacterial materials development. At present, the sterilization technology of washing machines has not been fully in combination with the distribution survey of microorganisms in washing machines. According to the specific microorganism distribution condition of the washing machine, the key distribution positions and the types of specific microorganisms contained in different positions, conduct more targeted sterilization treatment. This will help to completely solve the problem of microbial growth in washing machines from the source.

Bacterial Contamination in the Different Parts of Household Washing Machine: New Insights from Chengdu, Western China

The moist and warm environment in the household washing machine provides ideal living conditions for the growth and survival of various microorganisms. However, the biodiversity of bacterial community in the different parts of washing machine from Chinese households has not been clarified. In this study, we assessed the bacterial communities in sealing strip, detergent drawer, inner drum, water filter and greywater of ten domestic washing machines quantitatively and qualitatively in Chengdu, southwestern China. The microbial cultivation results indicated that the washing machines from Chengdu had a severe microbial contamination reflected by large counts on bacteria, fungi and coliform. Furthermore, the sequencing data showed that the different parts displayed distinctive bacterial compositions. At the level of genus, the anaerobic bacteria of Caproiciproducens and Acidipropionibacterium were predominant in sealing strip. Barnesiella, Shinella and Sellimonas were detected as the characteristic bacteria in detergent drawer. The pathogens of Luteibacter and Corynebacterium at the genus level were the dominant bacteria in inner drum and water filter, respectively. The genera of Azospira, Roseococcus, Elstera and Aquicella, which belonged to the pathogenic phylum of Proteobacteria, were identified as bioindicators for the greywater. Gene function analysis on the sequencing data illustrated that the bacteria from washing machines were potentially associated with bacterial infectious diseases and antimicrobial resistance. This study shows the bacterial diversity in the different parts of washing machines, providing new clues for bacterial contamination in washing machines from Chinese households.

Evaluation of building washing machines as an extreme environment for potentially pathogenic fungi

Washing machines are commonly used in households and are considered indispensable appliances for maintaining cleanliness and hygiene. Environmental conditions within household washing machines are ideal for fungal colonization, which may pose risks to human health and contribute to sick building syndrome. This study aimed to investigate the fungal species contamination in the building washing machines. A total of 50 building washing machines were swab-sampled at three locations: the detergent drawer, the inner and outer parts of the rubber door seal. The housekeeping conditions of these appliances were assessed through a questionnaire. The isolated fungi were identified using standard mycological diagnostic procedures and molecular analysis based on the ITS1/ITS4 and β-tubulin gene regions. The possibility of fungal agents transferring from contaminated washing machines to autoclaved clothes during laundry cycles was investigated. Fungi were detected in 82% of the sampled appliances, with the inner rubber door seal being the most frequently colonized area. Using conventional and molecular techniques, we identified 122 fungal isolates, encompassing 17 diverse genera of molds, yeast-like, and yeast fungi. The mold fungi included 14 genera of hyaline and black genus. Among these, the most frequently identified genera of hyaline and black fungi were Aspergillus (27.7%), and Cladosporium (10.7%), respectively. This study demonstrates that building washing machines may serve as suitable ecological niches for fungal growth and transmission. Therefore, regular cleaning and disinfection of these devices are necessary.

Aspergilli series Versicolores: importance of species identification in the clinical setting

The moulds of the genus Aspergillus section Nidulantes series Versicolores are ubiquitous and particularly recurrent in indoor air. They are considered present in 70% of the bioaerosols to which we are exposed most of our time spent indoors. With the taxonomic revision proposed in 2012 and the discovery of four new species, the series Versicolores currently includes 18 species. These moulds, although considered as cryptic (except Aspergillus sydowii), are opportunistic pathogens that can exhibit increased minimal inhibitory concentrations to conventional antifungal agents. In this review, we discuss the ecology and clinical implications of each species belonging to the series Versicolores. This survey also highlights the lack of consideration for taxonomic revisions in clinical practice and in scientific studies which greatly limits the acquisition of specific knowledge on species belonging to the series Versicolores.

Mycological Investigation of Bottled Water Dispensers in Healthcare Facilities

The usage of bottled water dispensers (BWDs) has spread worldwide. Despite their popularity, few studies have dealt with their microbial contaminants, and little attention is given to their fungal contamination. To our knowledge this is the first mycological study of BWDs in Europe. 36 devices have been examined in Budapest, Hungary. Despite of the strictly regulated water hygiene system in Hungary, molds and yeasts were detected in 86.8% of the samples, 56.76% were highly contaminated. Elevated heterotrophic plate counts were also observed in all samples compared to that of Hungarian drinking water. As all physical and chemical water quality characteristics have met the relevant national and European parametric values and neither totally explained the results of microbial counts, the effect of usage and maintenance habits of the devices were examined. Fungal concentrations were affected by the time elapsed since disinfection, days remaining until expiration of bottles, month of sampling and exposure to sunlight during storage. Microbes are able to proliferate in the bottled water and disperse inside the BWDs. Many of the detected fungal species (Sarocladium kiliense, Acremonium sclerotigenum/egyptiacum, Exophiala jeanselmei var. lecanii-corni, Exophiala equina, Meyerozyma guilliermondii, Cystobasidium slooffiae, Aspergillus jensenii, Bisifusarium biseptatum) are opportunistic pathogens for subpopulations of sensitive age groups and patients with immunodeficient conditions, including cystic fibrosis. Thus BWDs may pose a health risk to visitors of healthcare institutions, especially to patients with oral lesions in dental surgeries. The study draws attention to the need to investigate microbial contamination of these devices in other countries as well.

Screening Mold Colonies by Using Two Toxicity Assays Revealed Indoor Strains of Aspergillus calidoustus Producing Ophiobolins G and K

The occurrence and toxin production of the opportunistic pathogen Aspergillus calidoustus in Finnish buildings is not well documented in the literature. We tracked and identified four A. calidoustus colonies cultivated from indoor settled dusts and revealed the biological activities of crude biomass extracts. The toxic substances were identified as 6-epi-ophiobolin K, ophiobolin K, and ophiobolin G by high-performance liquid chromatography–mass spectrometry (HPLC-MS) based on chromatographic and mass spectrometry data (MS and MS/MS) on the crude extract of A. calidoustus strain MH34. A total of 29 fungal colonies collected from settled dust in an office room reported for indoor-air-related illnesses were screened for toxins that inhibited boar sperm motility in the BSMI (boar sperm motility inhibiting) assay and cell proliferation in the ICP (inhibition of cell proliferation) assays with PK-15 cells. Out of the 27 colonies tested as toxic, 12 colonies exhibiting conidiophores representative of the genera Chaetomium, Penicillium, and Paecilomyces were excluded from the study, while 13 colonies exhibited Aspergillus-like conidiophores. Biomass suspensions of these colonies were divided into two categories: Category 1 colonies (n = 4), toxic in the BSMI assay and the ICP assays, emitted blue fluorescence and grew at 37 °C; Category 2 colonies (n = 9), only toxic in the ICP assay, emitted orange fluorescence and exhibited limited or no growth at 37 °C. Colonies in Category 1 were pure-cultured, and the strains were named as MH4, MH21, MH34, MH36. Strain MH34 was identified as A. calidoustus by the internal transcribed spacer (ITS) sequences. Ethanol-soluble dry substances extracted from the biomass of the pure cultures exhibited a toxicological profile in the BSMI assay, SMID (sperm membrane integrity damage) assay, and ICP assay similar to that exhibited by pure ophiobolin A. Overall, the viable conidia of A. calidoustus in indoor settled dusts deserve attention when potentially hazardous mold species are monitored.