Possible transfer of plasmid mediated third generation cephalosporin resistance between Escherichia coli and Shigella sonnei in the human gut

Choice of antibiotic for treatment of serious bacterial infection is rapidly diminishing by plasmid mediated transfer of antibiotic resistance. Here, we report a possible horizontal transfer of plasmid carrying third-generation-cephalosporin (TGC) resistance between Escherichia coli and Shigella sonnei. Two different types of colonies were identified in MacConkey agar plate from a faecal specimen collected from a patient with shigellosis. The colonies were identified as E. coli and S. sonnei. Both of the isolates were resistant to ampicillin, chloramphenicol, co-trimoxazole, erythromycin, azithromycin, nalidixic acid, ceftriaxone, cefixime, ceftazidime, cefotaxime and susceptible to co-amoxiclave, amikacin, imipenam, astreonam, levofloxacin, moxifloxacin, mecillinam. These two strains were positive for extended spectrum β-lactamase. We were able to transfer ESBL producing property from both ceftriaxone-resistant isolates to the ceftriaxone susceptible recipient E. coli K12 and S. sonnei. Plasmid profile analysis revealed that the first-generation E. coli K12 and S. sonnei transconjugants harbored a 50MDa R plasmid, as two-parent ESBL-producing S. sonnei and E. coli strains. Similar patterns of ESBL producing plasmid and transferable antimicrobial phenotype suggests that the ESBL producing plasmid might transferred between E. coli and S. sonnei through conjugation in the human gut.