Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark.
Retired, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Sci Rep. 2017 Aug 2;7(1):7167. doi: 10.1038/s41598-017-07772-x.
This study assesses a novel bile solubility test and MALDI-TOF for the differentiation of Streptococcus pneumoniae from other mitis group streptococci, including differentiation of S. pneumoniae from Streptococcus pseudopneumoniae. Eighty-four species verified mitis group isolates were subjected to our bile solubility test (which measures and calculates the differences of absorbance in the test tube containing 10% sodium deoxycholate versus a blank control tube, after incubation for 10 minutes at 36 °C using a spectrophotometer) and MALDI-TOF MS (both the standard result output and by visual spectra evaluation). Applying a calculated optimal cut-off absorbance-value of 2.1, differentiated S. pneumoniae from all but one other mitis group streptococci (one S. mitis isolate generated an OD-value above 2.1). MALDI-TOF score value identification identified correctly 46 S. pneumoniae and 4 S. pseudopneumoniae but misidentified 16 other mitis group strains. Visual spectra evaluation correctly identified all S. pneumoniae and S. pseudopneumoniae strains but misidentified 13 other mitis group strains. The bile solubility test based on spectrophotometric reading described in this study can differentiate S. pneumoniae from other Streptococcus species. Combining the bile solubility test and the MALDI-TOF spectra results provide a correct identification of all S. pneumoniae and S. pseudopneumoniae isolates.
本研究评估了一种新型胆汁溶解度试验和 MALDI-TOF 用于区分肺炎链球菌与其他米蒂斯组链球菌，包括区分肺炎链球菌与肺炎链球菌。84 种经证实的米蒂斯组分离株进行了我们的胆汁溶解度试验（该试验测量并计算了在含有 10%脱氧胆酸钠的试管中与空白对照管相比的吸光度差异，在 36°C 孵育 10 分钟后，使用分光光度计）和 MALDI-TOF MS（标准结果输出和通过目视光谱评估）。应用计算出的最佳截止吸光度值 2.1，将肺炎链球菌与除一种其他米蒂斯组链球菌（一种米蒂斯链球菌分离株的 OD 值高于 2.1）区分开来。MALDI-TOF 得分值识别正确地识别了 46 株肺炎链球菌和 4 株肺炎链球菌，但错误地识别了 16 株其他米蒂斯组菌株。目视光谱评估正确地识别了所有肺炎链球菌和肺炎链球菌，但错误地识别了 13 株其他米蒂斯组菌株。本研究中基于分光光度读数描述的胆汁溶解度试验可以区分肺炎链球菌与其他链球菌。结合胆汁溶解度试验和 MALDI-TOF 光谱结果，可以正确识别所有肺炎链球菌和肺炎链球菌分离株。
