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Method for isolation of both lactose-fermenting and – non-fermenting Escherichia albertii strains from stool samples

Andrée F. Maheux, Stéphanie Brodeur, Ève Bérubé, Dominique K. Boudreau, Jehane Y. Abed, Maurice Boissinot, Luc Bissonnette, Michel G. Bergeron
Journal of microbiological methods 2018 v.154 pp. 134-140
Escherichia albertii, bacteria, feces, fermentation, isolation techniques, lactose, pathogenicity, phenotype, polymerase chain reaction, species identification
Initially, Escherichia albertii has been described as a non-lactose fermenting bacterium and methods used to isolate it were first based on this phenotypic property. However, a recent study showed a variable lactose fermentation phenotype for E. albertii suggesting that this microorganism could have been underestimated by previous studies using isolation methods based on lactose fermentation. In this study, we present a method for the isolation and identification of both lactose fermenting and non-fermenting-E. albertii cells in stool samples, said method combining culture and isolation on mEA agar, an indole test, as well as an E. albertii-specific PCR assay for formal species identification. The ability of the procedure to detect E. albertii strains was verified using 19 E. albertii strains and 132 non-E. albertii strains representing 88 species of different origins majoritary belonging to the Enterobacteriaceae family. All indole-positive white colonies grown on mEA agar were subjected to E. albertii-specific PCR amplification; all E. albertii strains tested were detected with this assay and none of the non-E. albertii strains tested was detected. To demonstrate the ability of the procedure to directly detect E. albertii in stool samples, E. albertii-inoculated stools were tested and for all inoculated samples, E. albertii colonies were easily detected and identified. The present study provides a method enable to recover both lactose-fermenting and -non-fermenting E. albertii strains from clinical samples. This method could help to provide a better portrait of the prevalence and pathogenicity of E. albertii in clinical samples.