Department of Infectious Diseases and Clinical Microbiology, Beijing Institute of Respiratory Medicine and Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China.
School of Public Health, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China.
Front Cell Infect Microbiol. 2023 Mar 7;13:1130645. doi: 10.3389/fcimb.2023.1130645. eCollection 2023.
Although the yeast () has been rarely reported in human infections, nosocomial outbreaks caused by this organism have been documented. Here we report a pseudo-outbreak of in a urology department of a Chinese hospital over a two-week period.
Three patients were admitted to the urology department of a tertiary teaching hospital in Beijing, China, from Nov to Dec 2018, for different medical intervention demands. During the period Nov 28 to Dec 5, funguria occurred in these three patients, and two of them had positive urine cultures multiple times. Sequencing of rDNA internal transcribed spacer (ITS) region and MALDI-TOF MS were applied for strain identification. Further, sequencing of rDNA non-transcribed spacer (NTS) region and whole genome sequencing approaches were used for outbreak investigation purpose.
All the cultured yeast strains were identified as by sequencing of ITS region, and were 100% identical to the type strain CBS 5640T. However, the MALDI-TOF MS system failed to correctly identify this yeast pathogen. Moreover, isolates from these three clustered cases shared 99.91%-100% identical NTS region sequences, which could not rule out the possibility of an outbreak. However, whole genome sequencing results revealed that only two of the cases were genetically-related with a pairwise SNP of 192 nt, whilst the third case had over 26,000 SNPs on its genome, suggesting a different origin. Furthermore, the genomes of the first three case strains were phylogenetically even more diverged when compared to a strain identified from another patient, who was admitted to a general surgical department of the same hospital 7 months later. One of the first three patients eventually passed away due to poor general conditions, one was asymptomatic, and other clinically improved.
In conclusion, nosocomial outbreaks caused by emerging and uncommon fungal species are increasingly being reported, hence awareness must be raised. Genotyping with commonly used universal gene targets may have limited discriminatory power in tracing the sources of infection for these organisms, requiring use of whole genome sequencing to confirm outbreak events.
尽管酵母（）在人类感染中很少被报道，但已经有文献记载由该病原体引起的医院感染暴发。在此，我们报告了在中国一家医院泌尿科发生的为期两周的酵母（）假暴发事件。
2018 年 11 月至 12 月期间，3 名患者因不同的医疗干预需求入住北京一家三级教学医院的泌尿科。11 月 28 日至 12 月 5 日期间，这 3 名患者均出现尿真菌，其中 2 人多次尿液培养阳性。采用 rDNA 内转录间隔区（ITS）和基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）测序进行菌株鉴定。进一步采用 rDNA 非转录间隔区（NTS）和全基因组测序方法进行暴发调查。
ITS 区测序均鉴定所有培养的酵母菌株为（），与 CBS 5640T 型株完全一致，而 MALDI-TOF MS 系统无法正确鉴定这种酵母病原体。此外，这 3 个聚集病例的分离株 NTS 区序列完全相同（99.91%-100%），不能排除暴发的可能性。然而，全基因组测序结果显示，只有 2 例与遗传相关，SNP 为 192nt，而第 3 例基因组上有超过 26000 个 SNP，提示来源不同。此外，与另一名在同一家医院普通外科就诊、7 个月后被鉴定为酵母感染的患者相比，前 3 例病例株的基因组进化更为分化。其中 1 例最终因一般情况较差而死亡，1 例无症状，其他患者临床状况改善。
总之，越来越多的新兴和罕见真菌物种引起的医院感染暴发被报道，因此必须提高认识。使用常用的通用基因靶标进行基因分型可能对追踪这些病原体的感染源的能力有限，需要使用全基因组测序来确认暴发事件。
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