Challenges in identification of enteroinvasive Escherichia coli and Shigella spp. in Lebanon

This study aimed to evaluate the routine identification tools available in Lebanon for differentiation of Escherichia coli and Shigella spp. The identification of 43 isolates defined as Shigella spp. by Api 20E was accessed using MALDI-TOF, serological testing, duplex PCR targeting ipaH (present in Shigella spp. and enteroinvasive E. coli "EIEC") and lacY (found in E. coli including EIEC but not Shigella spp.) as well as gyrB gene sequencing. Antibiotic susceptibility was investigated as well as Shiga-toxin production. All isolates were identified as E. coli by MALDI-TOF while the PCR showed a disparate group of 26 EIEC, 11 Shigella spp., 5 E. coli and 1 inactive E. coli. However, the sequencing of gyrB gene, which was recently described as a suitable marker for distinguishing E. coli and Shigella spp., identified all isolates as E. coli. Antibiotic resistance was noticeable against ß-lactams, rifampicin, trimethoprim-sulfamethoxazole, gentamicin, and ciprofloxacin. The most common variants of beta-lactamase genes were blaTEM-1, blaCTX-M-15, and blaCTX-M-3. A great discordance between the used methods in identification was revealed herein. An accurate identification technique able to distinguish E. coli from Shigella spp. in routine laboratories is a pressing need in order to select the appropriate treatment and assess the epidemiology of these bacteria.