Jadhav Snehal, Gulati Vandana, Fox Edward M, Karpe Avinash, Beale David J, Sevior Danielle, Bhave Mrinal, Palombo Enzo A
Department of Chemistry and Biotechnology, Faculty of Science, Engineering and Technology, Swinburne University of Technology, P.O. Box 218, Hawthorn 3122, Victoria, Australia.
Food and Nutrition, Commonwealth Scientific and Industrial Research Organisation (CSIRO), 671 Sneydes Road, Werribee, Victoria 3030, Australia.
Int J Food Microbiol. 2015 Jun 2;202:1-9. doi: 10.1016/j.ijfoodmicro.2015.01.023. Epub 2015 Feb 24.
Listeria monocytogenes is an important foodborne pathogen responsible for the sometimes fatal disease listeriosis. Public health concerns and stringent regulations associated with the presence of this pathogen in food and food processing environments underline the need for rapid and reliable detection and subtyping techniques. In the current study, the application of matrix assisted laser desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) as a single identification and source-tracking tool for a collection of L. monocytogenes isolates, obtained predominantly from dairy sources within Australia, was explored. The isolates were cultured on different growth media and analysed using MALDI-TOF MS at two incubation times (24 and 48 h). Whilst reliable genus-level identification was achieved from most media, identification at the species level was found to be dependent on culture conditions. Successful speciation was highest for isolates cultured on the chromogenic Agar Listeria Ottaviani Agosti agar (ALOA, 91% of isolates) and non-selective horse blood agar (HBA, 89%) for 24h. Chemometric statistical analysis of the MALDI-TOF MS data enabled source-tracking of L. monocytogenes isolates obtained from four different dairy sources. Strain-level discrimination was also observed to be influenced by culture conditions. In addition, t-test/analysis of variance (ANOVA) was used to identify potential biomarker peaks that differentiated the isolates according to their source of isolation. Source-tracking using MALDI-TOF MS was compared and correlated with the gold standard pulsed-field gel electrophoresis (PFGE) technique. The discriminatory index and the congruence between both techniques were compared using the Simpsons Diversity Index and adjusted Rand and Wallace coefficients. Overall, MALDI-TOF MS based source-tracking (using data obtained by culturing the isolates on HBA) and PFGE demonstrated good congruence with a Wallace coefficient of 0.71 and comparable discriminatory indices of 0.89 and 0.86, respectively. MALDI-TOF MS thus represents a rapid and cost-effective source-tracking technique for L. monocytogenes.
单核细胞增生李斯特菌是一种重要的食源性病原体，可引发有时会致命的李斯特菌病。与该病原体在食品及食品加工环境中的存在相关的公共卫生问题及严格规定凸显了对快速且可靠的检测及分型技术的需求。在当前研究中，探索了将基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）用作对主要从澳大利亚乳制品来源获得的一批单核细胞增生李斯特菌分离株进行单一鉴定及溯源工具的应用。将这些分离株在不同生长培养基上培养，并在两个培养时间点（24小时和48小时）使用MALDI-TOF MS进行分析。虽然从大多数培养基上都能实现可靠的属水平鉴定，但发现种水平鉴定取决于培养条件。在显色李斯特菌奥塔维亚尼-阿戈斯蒂琼脂（ALOA，91%的分离株）和非选择性马血琼脂（HBA，89%）上培养24小时的分离株，成功进行种鉴定的比例最高。对MALDI-TOF MS数据进行化学计量统计分析能够对从四个不同乳制品来源获得的单核细胞增生李斯特菌分离株进行溯源。还观察到菌株水平的区分也受培养条件影响。此外，使用t检验/方差分析（ANOVA）来识别根据分离来源区分分离株的潜在生物标志物峰。将使用MALDI-TOF MS进行溯源与金标准脉冲场凝胶电泳（PFGE）技术进行比较和关联。使用辛普森多样性指数以及调整后的兰德系数和华莱士系数比较了两种技术的鉴别指数和一致性。总体而言，基于MALDI-TOF MS的溯源（使用在HBA上培养分离株获得的数据）和PFGE显示出良好的一致性，华莱士系数为0.71，鉴别指数分别为0.89和0.86，具有可比性。因此，MALDI-TOF MS是一种用于单核细胞增生李斯特菌的快速且经济高效的溯源技术。
