Misra Sikha, Sharma Savitri, Barik Manas Ranjan, Rani Nisha, Das Sujata, Sahu Srikant Kumar, Priyadarshini Smruti Rekha, Behera Himansu Sekhar
Cornea & Anterior Segment Services, L V Prasad Eye Institute, Bhubaneswar, 751024, Odisha, India.
Ocular Microbiology Services, L V Prasad Eye Institute, Bhubaneswar, 751024, Odisha, India.
J Ophthalmic Inflamm Infect. 2025 May 26;15(1):45. doi: 10.1186/s12348-025-00479-5.
To report a case series of microbial keratitis showing atypical yeast-like structures in direct microscopy which were culture-negative but subsequently identified as yeast cells by PCR and DNA sequencing.
This is a retrospective, non-comparative case series of eight patients with infectious keratitis, where smear examination (potassium hydroxide + calcofluor white) showed spore like structures resembling yeast. There was no growth in any solid culture media. Routine PCR assay was performed using pan fungal primers followed by Sanger sequencing and nucleotide sequences were analysed using NCBI-BLAST software. Medical treatment in all patients were initiated based on clinical suspicion and presumptive microbiology report. Therapeutic penetrating keratoplasty was performed for patients not responding to medical antifungal therapy. Demographic, clinical data were collected for each patient from electronic medical records of the patients and outcome analysed. Amplification of fungal DNA was seen in the PCR assay of all samples. Nucleotide sequences of the amplicons obtained after Sanger sequencing and NCBI-BLAST analysis were found identical to Candida albicans (n = 7) and Citeromyces matriensis (n = 1). Patients were treated with antifungal drugs such as topical natamycin 5% or amphotericin B 0.15%. Ulcer resolved with scarring in 5 patients (62.5%), one patient had failed graft after therapeutic penetrating keratoplasty (12.5%), one (12.5%) eye became phthisical and one patient (12.5%) was lost to follow up.
Atypical structures resembling yeast-like cells detected in direct smear examination in the absence of growth in culture media should raise the suspicion of a fungal etiology and warrant further investigations to establish the diagnosis.
报告一组微生物性角膜炎病例系列，其在直接显微镜检查中显示出非典型酵母样结构，培养结果为阴性，但随后通过聚合酶链反应（PCR）和DNA测序鉴定为酵母细胞。
这是一项针对8例感染性角膜炎患者的回顾性、非对照病例系列研究。涂片检查（氢氧化钾+荧光增白剂）显示出类似酵母的孢子样结构。在任何固体培养基中均未生长。使用泛真菌引物进行常规PCR检测，随后进行桑格测序，并使用NCBI-BLAST软件分析核苷酸序列。所有患者均根据临床怀疑和推测性微生物学报告开始进行药物治疗。对于对抗真菌药物治疗无反应的患者，进行了治疗性穿透性角膜移植术。从患者的电子病历中收集每位患者的人口统计学、临床数据并分析结果。所有样本的PCR检测均可见真菌DNA扩增。桑格测序和NCBI-BLAST分析后获得的扩增子核苷酸序列与白色念珠菌（n = 7）和马氏有孢圆酵母（n = 1）相同。患者接受了抗真菌药物治疗，如局部使用5%的那他霉素或0.15%的两性霉素B。5例患者（62.5%）溃疡愈合并形成瘢痕，1例患者在治疗性穿透性角膜移植术后移植失败（12.5%），1例（12.5%）眼萎缩，1例患者（12.5%）失访。
在直接涂片检查中检测到类似酵母样细胞的非典型结构，而培养基中无生长，应怀疑真菌病因，并需进一步检查以明确诊断。
