The Enterobacter cloacae complex (ECC) comprises 13 genetic groups that are widespread in varied environmental niches and demonstrate highly diverse phenotypic and genotypic profiles. They are also of clinical importance, being responsible for a range of community associated and nosocomial infections in humans, including nosocomial outbreaks. The most frequent isolates of ECC from humans are Enterobacter hormaechei and cluster III, which are definitively classified only by sequence analysis of their hsp60, rpoB, or hemB genes. Such identification cannot be used for routine diagnosis, but the qPCR platform fits the purpose. It has evolved rapidly, and is embedded in many microbiological disciplines as a specific, sensitive, high-throughput, rapid, and cost effective molecular method. We designed novel qPCR assays for identifying Enterobacter hormaechei and ECC cluster III.
The assays were developed targeting unique sequences and SNPs in the hsp60 gene. Validation included 112 different organisms, including ATCC, environmental and clinical strains. The sensitivity of the cluster III and Enterobacter hormaechei assays were 100%, 97% and specificity 100% and 97%, respectively. Blood culture isolates were mainly assigned to E. hormaechei or to cluster III, while isolates from other clinical sources were more varied. A statistically significant difference in the distribution of cluster III was demonstrated between blood and non-blood sources (p<0.5). These results emphasize the importance of accurate and rapid identification of Enterobacter hormaechei and ECC cluster III.
