Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Ljubljana, Slovenia.
BMC Microbiol. 2019 Dec 19;19(1):300. doi: 10.1186/s12866-019-1674-5.
In modern lifestyles, people make their everyday tasks easier by using household appliances, for example dishwashers. Previous studies showed massive contamination of dishwasher rubber seals with fungi, thus bacterial community, able to survive under harsh conditions, remain undetermined.
Bacteria that colonise the extreme environment of household dishwasher rubber seals were investigated using cultivation-dependent and metagenomic approaches. All bacterial isolates were tested for resistance to seven selected antibiotics. Same time bacterial diversity of tap water, connected to the dishwashers was investigated.
All 30 dishwashers investigated were colonised by various bacteria. Cultivation approaches resulted in 632 bacterial isolates in total, belonging to four phyla, eight classes, 40 genera and 74 species. The majority were Gram-positive, as solely Firmicutes (dominated by the Bacillus cereus group) and Actinobacteria. Gammaproteobacteria were primarily represented by Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Escherichia coli. Metagenomic assessment of the bacterial biodiversity of the dishwasher rubber seals confirmed the predominance of Gram-positive bacteria, as primarily Actinobacteria, followed by Proteobacteria dominated by Gammaproteobacteria, and by pathogenic species such as Escherichia sp., Acinetobacter baumannii, Pseudomonas sp., Stenotrophomonas maltophilia, and Enterobacter sp.. Metagenomic assessment of bacterial biodiversity in the tap water connected to dishwashers revealed predominance of Gram-negative bacteria, in particular Proteobacteria, mainly represented by Tepidimonas sp.. Actinobacteria showed low numbers while no Firmicutes were detected in the tap water. The bacterial diversity of tap water was also lower, 23 genera compared to 39 genera on dishwasher rubber seals. Only 13 out of 49 genera identified by metagenomics approach was found in both environments, of those Gordonia was enriched while half of 13 genera were depleted in dishwashers compared to tap water.
These data indicate that colonisation of dishwasher rubber seals probably depends primarily on the bacterial input from the dirty vessels, and much less on the bacteria in the tap water. Based on the antibiotic resistance data, the dishwasher rubber seal bacterial isolates do not represent a serious threat for the spread of antibiotic resistance into the household environment. Nevertheless dishwashers cannot be ignored as potential sources of human infections, in particular for immuno-compromised individuals.
在现代生活方式中，人们使用家用电器（例如洗碗机）来使日常任务变得更加轻松。先前的研究表明，洗碗机橡胶密封件受到真菌的严重污染，因此能够在恶劣条件下生存的细菌群落仍未确定。
使用培养依赖和宏基因组学方法研究了在家用洗碗机橡胶密封件极端环境中定殖的细菌。测试了所有细菌分离株对七种选定抗生素的抗性。同时，还研究了与洗碗机相连的自来水的细菌多样性。
在所调查的 30 台洗碗机中，均有各种细菌定殖。培养方法总共产生了 632 个细菌分离株，它们属于四个门，八个纲，40 个属和 74 个种。大多数为革兰氏阳性菌，仅为Firmicutes（主要由芽孢杆菌属组成）和Actinobacteria。 gammaproteobacteria 主要由 Stenotrophomonas maltophilia，Pseudomonas aeruginosa 和 Escherichia coli 组成。对洗碗机橡胶密封件细菌生物多样性的宏基因组评估证实了革兰氏阳性菌的优势，主要是Actinobacteria，其次是由 gammaproteobacteria 主导的 Proteobacteria，以及致病性物种，例如 Escherichia sp.，Acinetobacter baumannii，Pseudomonas sp.，stenotrophomonas maltophilia 和 Enterobacter sp.。对与洗碗机相连的自来水的细菌生物多样性的宏基因组评估显示，革兰氏阴性菌占主导地位，尤其是 Proteobacteria，主要由 Tepidimonas sp. 组成。放线菌的数量较低，而自来水中未检测到Firmicutes。与洗碗机橡胶密封件相比，自来水中的细菌多样性也较低，只有 23 个属，而宏基因组学方法鉴定的 49 个属中只有 13 个在这两个环境中都有发现，其中 Gordonia 被富集，而在洗碗机中，有一半的 13 个属的丰度都低于自来水。
这些数据表明，洗碗机橡胶密封件的定殖可能主要取决于来自脏污容器的细菌输入，而来自自来水的细菌输入则要少得多。根据抗生素耐药性数据，洗碗机橡胶密封件细菌分离株不会对家庭环境中抗生素耐药性的传播构成严重威胁。然而，洗碗机不能被忽视为人类感染的潜在来源，特别是对于免疫功能低下的个体。
