Jaradat Ziad W, Ababneh Qotaiba O, Saadoun Ismail M, Samara Nawal A, Rashdan Abrar M
Department of Biotechnology and Genetic Engineering, Jordan University of Science and Technology, Irbid, Jordan.
BMC Microbiol. 2009 Oct 27;9:225. doi: 10.1186/1471-2180-9-225.
Cronobacter spp. (formerly Enterobacter sakazakii), are a group of Gram-negative pathogens that have been implicated as causative agents of meningitis and necrotizing enterocolitis in infants. The pathogens are linked to infant formula; however, they have also been isolated from a wide range of foods and environmental samples.
In this study, 233 samples of food, infant formula and environment were screened for the presence of Cronobacter spp. in an attempt to find its source. Twenty nine strains were isolated from samples of spices, herbs, infant foods, and dust obtained from household vacuum cleaners. Among the 76 samples of infant food, infant formula, milk powder and non-milk dairy products tested, only one sample of infant food contained Cronobacter spp. (1.4%). The other Cronobacter spp. isolates recovered include two from household vacuum dust, and 26 from 67 samples of herbs and spices. Among the food categories analyzed, herbs and spices harbored the highest number of isolates, indicating plants as a possible reservoir of this pathogen. Initial screening with API 20E test strips yielded 42 presumptive isolates. Further characterization using 3 chromogenic media (alpha-MUG, DFI and EsPM) and 8 sets of PCR primers detecting ITS (internal transcribed spacer sequences), 16S rRNA, zpx, gluA, gluB, OmpA genes followed by nucleotide sequencing of some PCR amplicons did not confirm the identity of all the isolates as none of the methods proved to be free of both false positives or false negatives. The final confirmation step was done by 16S rRNA sequence analysis identifying only 29 of the 42 isolates as Cronobacter spp.
Our studies showed that Cronobacter spp. are highly diverse and share many phenotypic traits with other Enterobacteriaceae members highlighting the need to use several methods to confirm the identity of this pathogen. None of the biochemical, chromogenic or PCR primers proved to be a reliable method for confirmation of the identity of the isolates as all of them gave either false positives or false negatives or both. It is therefore concluded that 16S rRNA sequencing is pivotal to confirm the identity of the isolates.
阪崎肠杆菌属（以前称为阪崎肠杆菌）是一组革兰氏阴性病原体，被认为是婴儿脑膜炎和坏死性小肠结肠炎的病原体。这些病原体与婴儿配方奶粉有关；然而，它们也从多种食品和环境样本中分离出来。
在本研究中，对233份食品、婴儿配方奶粉和环境样本进行了阪崎肠杆菌属检测，以试图找到其来源。从香料、草药、婴儿食品以及家用吸尘器收集的灰尘样本中分离出29株菌株。在测试的76份婴儿食品、婴儿配方奶粉、奶粉和非乳制乳制品样本中，只有一份婴儿食品样本含有阪崎肠杆菌属（1.4%）。其他分离出的阪崎肠杆菌属包括两份来自家用吸尘器灰尘，以及67份草药和香料样本中的26份。在所分析的食品类别中，草药和香料中分离出的菌株数量最多，表明植物可能是这种病原体的储存宿主。使用API 20E测试条进行初步筛选得到42株疑似菌株。进一步使用3种显色培养基（α-MUG、DFI和EsPM）和8组检测ITS（内转录间隔区序列）、16S rRNA、zpx、gluA、gluB、OmpA基因的PCR引物进行鉴定，随后对一些PCR扩增产物进行核苷酸测序，由于没有一种方法能完全避免假阳性或假阴性，因此未能确认所有分离株的身份。最终确认步骤通过16S rRNA序列分析完成，42株分离株中仅鉴定出29株为阪崎肠杆菌属。
我们的研究表明，阪崎肠杆菌属具有高度多样性，并且与其他肠杆菌科成员共享许多表型特征，这突出了需要使用多种方法来确认该病原体的身份。生化、显色或PCR引物均未被证明是确认分离株身份的可靠方法，因为它们都出现了假阳性或假阴性或两者皆有。因此得出结论，16S rRNA测序对于确认分离株的身份至关重要。
