Molecular validation of clinical Pantoea isolates identified by MALDI-TOF

The Enterobacterial genus Pantoea contains both free-living and host-associating species, with considerable debate as to whether documented reports of human infections by members of this species group are accurate. MALDI-TOF-based identification methods are commonly used in clinical laboratories as a rapid means of identification, but its reliability for identification of Pantoea species is unclear. In this study, we carried out cpn60-based molecular typing of 54 clinical isolates that had been identified as Pantoea using MALDI-TOF and other clinical typing methods. We found that 24% had been misidentified, and were actually strains of Citrobacter, Enterobacter, Kosakonia, Klebsiella, Pseudocitrobacter, members of the newly described Erwinia gerundensis, and even several unclassified members of the Enterobacteriaceae. The 40 clinical strains that were confirmed to be Pantoea were identified as Pantoea agglomerans, Pantoea allii, Pantoea dispersa, Pantoea eucalypti, and Pantoea septica as well as the proposed species group, Pantoea latae. Some species groups considered largely environmental or plant-associated, such as P. allii and P. eucalypti were also among clinical specimens. Our results indicate that MALDI-TOF-based identification methods may misidentify strains of the Enterobacteriaceae as Pantoea.泛菌属（Pantoea）是肠杆菌科下的一个属，包含自由生活及与宿主共生的物种，目前学界对该类群成员引发人类感染的已报道案例是否准确存在较大争议。基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）鉴定方法作为快速鉴定手段，广泛应用于临床实验室，但其对泛菌属物种的鉴定可靠性尚不明确。本研究针对54株经MALDI-TOF及其他临床分型方法鉴定为泛菌属的临床分离株，开展了基于cpn60的分子分型分析。结果显示，其中24%的分离株存在鉴定错误，实际为柠檬酸杆菌属（Citrobacter）、肠杆菌属（Enterobacter）、科斯菌属（Kosakonia）、克雷伯菌属（Klebsiella）、假柠檬酸杆菌属（Pseudocitrobacter）、新报道的Erwinia gerundensis类群成员，甚至肠杆菌科的若干未分类菌株。经确认属于泛菌属的40株临床菌株，经鉴定为成团泛菌（Pantoea agglomerans）、葱泛菌（Pantoea allii）、分散泛菌（Pantoea dispersa）、桉树泛菌（Pantoea eucalypti）、败血泛菌（Pantoea septica）以及提议建立的类群——宽体泛菌（Pantoea latae）。部分通常被认为主要为环境或植物相关的类群，如葱泛菌和桉树泛菌，也在临床样本中被检出。本研究结果表明，基于MALDI-TOF的鉴定方法可能会将肠杆菌科菌株误鉴定为泛菌属菌株。