Townsend Stacy M, Hurrell Edward, Caubilla-Barron Juncal, Loc-Carrillo Catherine, Forsythe Stephen J
Nottingham Trent University, School of Science and Technology, Clifton Lane, Nottingham NG11 8NS, UK.
Microbiology (Reading). 2008 Dec;154(Pt 12):3659-3667. doi: 10.1099/mic.0.2008/021980-0.
Enterobacter hormaechei is a Gram-negative bacterium within the Enterobacter cloacae complex, and has been shown to be of clinical significance by causing nosocomial infections, including sepsis. Ent. hormaechei is spread via horizontal transfer and is often associated with extended-spectrum beta-lactamase production, which increases the challenges associated with treatment by limiting therapeutic options. This report considers 10 strains of Ent. hormaechei (identified by 16S rDNA sequencing) that had originally been identified by phenotyping as Cronobacter (Enterobacter) sakazakii. Seven strains were from different neonates during a nosocomial outbreak in a California hospital. PFGE analysis revealed a clonal relationship among six of the seven isolates and therefore a previously unrecognized Ent. hormaechei outbreak had occurred over a three-month period. Antibiotic-resistance profiles were determined and extended-spectrum beta-lactamase activity was detected. The association of the organism with powdered infant formula, neonatal hosts and Cr. sakazakii suggested that the virulence of these organisms may be similar. Virulence traits were tested and all strains were shown to invade both gut epithelial (Caco-2) and blood-brain barrier endothelial cells (rBCEC4), and to persist in macrophages (U937). Due to misidentification we suggest that Ent. hormaechei may be an under-reported cause of bacterial infection, especially in neonates. Also, its isolation from various sources, including powdered infant milk formula, makes it a cause for concern and merits further investigation.
霍氏肠杆菌是阴沟肠杆菌复合体中的一种革兰氏阴性菌，已被证明具有临床意义，可引起包括败血症在内的医院感染。霍氏肠杆菌通过水平转移传播，且常与超广谱β-内酰胺酶的产生有关，这通过限制治疗选择增加了治疗相关的挑战。本报告考虑了10株最初通过表型鉴定为阪崎肠杆菌（阴沟肠杆菌）的霍氏肠杆菌（通过16S rDNA测序鉴定）。7株来自加利福尼亚一家医院医院感染暴发期间的不同新生儿。脉冲场凝胶电泳分析揭示了7株分离株中有6株存在克隆关系，因此在三个月期间发生了一次先前未被认识的霍氏肠杆菌暴发。确定了抗生素耐药谱并检测到超广谱β-内酰胺酶活性。该菌与婴儿配方奶粉、新生儿宿主以及阪崎肠杆菌的关联表明这些菌的毒力可能相似。对毒力特性进行了测试，结果显示所有菌株均可侵袭肠道上皮细胞（Caco-2）和血脑屏障内皮细胞（rBCEC4），并可在巨噬细胞（U937）中存活。由于错误鉴定，我们认为霍氏肠杆菌可能是细菌感染，尤其是新生儿细菌感染的一个未被充分报道的病因。此外，从包括婴儿配方奶粉在内的各种来源分离出该菌，令人担忧，值得进一步研究。
