Rodríguez-Leguizamón Giovanni, Fiori Alessandro, López Luisa F, Gómez Beatriz L, Parra-Giraldo Claudia M, Gómez-López Arley, Suárez Carlos F, Ceballos Andrés, Van Dijck Patrick, Patarroyo Manuel A
School of Medicine and Health Sciences, Universidad del Rosario, Bogotá, Colombia.
VIB Department of Molecular Microbiology, Leuven, Belgium.
BMC Microbiol. 2015 Oct 5;15:199. doi: 10.1186/s12866-015-0535-0.
Candida species are the most frequently found fungal pathogens causing nosocomial disease in a hospital setting. Such species must be correctly identified to ensure that appropriate control measures are taken and that suitable treatment is given for each species. Candida albicans is causing most fungal disease burden worldwide; the challenge lies in differentiating it from emerging atypical, minor and related species such as Candida dubliniensis and Candida africana. The purpose of this study was to compare identification based on MALDI-TOF MS to standard identification systems using a set of nosocomial isolates.
Eleven nosocomial samples were collected from 6 third-level hospitals in Bogotá, Colombia. All the samples were identified by combining MALDI-TOF MS with morphological characters, carbohydrate assimilation and molecular markers (D1/D2 and HWP1).
The present work describes the first collection of atypical Colombian Candida clinical isolates; these were identified as Candida albicans/Candida africana by their MALDI-TOF MS profile. Phenotypical characteristics showed that they were unable to produce chlamydospores, assimilate trehalose, glucosamine, N- acetyl-glucosamine and barely grew at 42 °C, as would be expected for Candida africana. The molecular identification of the D1/D2 region of large subunit ribosomal RNA and HWP1 hyphal cell wall protein 1 sequences from these isolates was consistent with those for Candida albicans. The mass spectra obtained by MALDI-TOF MS were analysed by multi-dimensional scaling (MDS) and cluster analysis, differences being revealed between Candida albicans, Candida africana, Candida dubliniensis reference spectra and two clinical isolate groups which clustered according to the clinical setting, one of them being clearly related to C. albicans.
This study highlights the importance of using MALDI-TOF MS in combination with morphology, substrate assimilation and molecular markers for characterising Candida albicans-related and atypical C. albicans species, thereby overcoming conventional identification methods. This is the first report of hospital-obtained isolates of this type in Colombia; the approach followed might be useful for gathering knowledge regarding local epidemiology which could, in turn, have an impact on clinical management. The findings highlight the complexity of distinguishing between typical and atypical Candida albicans isolates in hospitals.
念珠菌属是医院环境中最常见的引起医院感染的真菌病原体。必须正确鉴定此类菌种，以确保采取适当的控制措施，并针对每种菌种给予合适的治疗。白色念珠菌在全球造成了大部分真菌疾病负担；挑战在于将其与新兴的非典型、少见及相关菌种，如都柏林念珠菌和非洲念珠菌区分开来。本研究的目的是使用一组医院分离株，比较基于基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）的鉴定方法与标准鉴定系统。
从哥伦比亚波哥大的6家三级医院收集了11份医院样本。所有样本均通过MALDI-TOF MS结合形态学特征、碳水化合物同化作用和分子标记（D1/D2和HWP1）进行鉴定。
本研究描述了首批哥伦比亚非典型念珠菌临床分离株的收集情况；通过MALDI-TOF MS图谱将它们鉴定为白色念珠菌/非洲念珠菌。表型特征显示，它们无法产生厚垣孢子，不能同化海藻糖、氨基葡萄糖、N-乙酰氨基葡萄糖，并且在42℃时几乎不生长，这与非洲念珠菌的预期情况相符。对这些分离株的大亚基核糖体RNA的D1/D2区域和HWP1菌丝细胞壁蛋白1序列进行分子鉴定，结果与白色念珠菌一致。通过多维标度分析（MDS）和聚类分析对MALDI-TOF MS获得的质谱图进行分析，发现白色念珠菌、非洲念珠菌、都柏林念珠菌参考图谱与两个根据临床背景聚类的临床分离株组之间存在差异，其中一组与白色念珠菌明显相关。
本研究强调了将MALDI-TOF MS与形态学、底物同化作用和分子标记相结合用于鉴定白色念珠菌相关及非典型白色念珠菌菌种的重要性，从而克服了传统鉴定方法。这是哥伦比亚首次关于此类医院获得性分离株的报告；所采用的方法可能有助于收集有关当地流行病学的知识，进而对临床管理产生影响。研究结果凸显了在医院中区分典型和非典型白色念珠菌分离株的复杂性。
