Dept. of Food Science, Purdue Univ., West Lafayette, IN 47907, USA.
J Food Sci. 2010 Aug 1;75(6):M340-6. doi: 10.1111/j.1750-3841.2010.01686.x.
FT-IR spectroscopy methods for detection, differentiation, and quantification of E. coli O157:H7 strains separated from ground beef were developed. Filtration and immunomagnetic separation (IMS) were used to extract live and dead E. coli O157:H7 cells from contaminated ground beef prior to spectral acquisition. Spectra were analyzed using chemometric techniques in OPUS, TQ Analyst, and WinDAS software programs. Standard plate counts were used for development and validation of spectral analyses. The detection limit based on a selectivity value using the OPUS ident test was 10(5) CFU/g for both Filtration-FT-IR and IMS-FT-IR methods. Experiments using ground beef inoculated with fewer cells (10(1) to 10(2) CFU/g) reached the detection limit at 6 h incubation. Partial least squares (PLS) models with cross validation were used to establish relationships between plate counts and FT-IR spectra. Better PLS predictions were obtained for quantifying live E. coli O157:H7 strains (R(2)> or = 0.9955, RMSEE < or = 0.17, RPD > or = 14) and different ratios of live and dead E. coli O157:H7 cells (R(2)= 0.9945, RMSEE = 2.75, RPD = 13.43) from ground beef using Filtration-FT-IR than IMS-FT-IR methods. Discriminant analysis and canonical variate analysis (CVA) of the spectra differentiated various strains of E. coli O157:H7 from an apathogenic control strain. CVA also separated spectra of 100% dead cells separated from ground beef from spectra of 0.5% live cells in the presence of 99.5% dead cells of E. coli O157:H7. These combined separation and FT-IR methods could be useful for rapid detection and differentiation of pathogens in complex foods.
建立了从绞碎牛肉中分离出的大肠杆菌 O157:H7 菌株的 FT-IR 光谱检测、区分和定量方法。在光谱采集之前，使用过滤和免疫磁分离（IMS）从污染的绞碎牛肉中提取活的和死的大肠杆菌 O157:H7 细胞。使用 OPUS、TQ Analyst 和 WinDAS 软件程序中的化学计量技术对光谱进行分析。标准平板计数用于光谱分析的开发和验证。使用 OPUS ident 测试的选择性值确定基于过滤-FT-IR 和 IMS-FT-IR 方法的检测限均为 10(5) CFU/g。使用接种较少细胞（10(1)至 10(2) CFU/g）的绞碎牛肉进行的实验在孵育 6 小时时达到检测限。使用偏最小二乘法（PLS）进行交叉验证的模型建立了平板计数与 FT-IR 光谱之间的关系。使用过滤-FT-IR 方法定量活的大肠杆菌 O157:H7 菌株（R(2)>或=0.9955，RMSEE<或=0.17，RPD>或=14）和不同比例的活的和死的大肠杆菌 O157:H7 细胞（R(2)=0.9945，RMSEE=2.75，RPD=13.43）的 PLS 预测更好，与 IMS-FT-IR 方法相比。对光谱的判别分析和典型变量分析（CVA）可区分大肠杆菌 O157:H7 的不同菌株与无病原体对照菌株。CVA 还分离了从绞碎牛肉中分离出的 100%死细胞的光谱，与存在 99.5%大肠杆菌 O157:H7 死细胞的情况下 0.5%活细胞的光谱分开。这些组合的分离和 FT-IR 方法可用于快速检测和区分复杂食品中的病原体。
