Studies on antimicrobial activity of some bacterial isolates against extended spectrum beta-lactamases producing Gram-negative bacteria

Abstract

A total number of 173 Streptomyces isolates were recovered from different soil samples. The recovered and collected isolates were screened for their antimicrobial activity against an extended spectrum beta-lactamase (ESBL) producer K. pneumoniae ATCC 700603 reference strain using agar plug method. Thirty isolates proved to have antimicrobial activity against the reference strain. The cell free culture supernatant (CFCS) of the thirty Streptomyces isolates were further screened for their antimicrobial activity against the same reference strain as well as against three different pathogenic ESBL producers using agar well diffusion method. Two Streptomyces isolates coded W2 and H21 gave the largest inhibition zones against all tested ESBL producers and were selected for completing the present study. They were identified by 16S rRNA gene sequencing as Streptomyces (S.) fulvissimus isolate W2 and Streptomyces (S.) manipurensis isolate H21 and were deposited in the National Center for Biotechnology Information (NCBI) GenBank database under the accession codes MH036743 and MH036744, respectively. The antibiotic susceptibility of S. fulvissimus isolate W2 showed sensitivity towards amikacin, ciprofloxacin, doxycycline, erythromycin, ertapenem, gentamicin, levofloxacin, linezolid, meropenem and vancomycin. On the other hand, S. manipurensis isolate H21 showed sensitivity towards amikacin, azithromycin, cephoxitin, ciprofloxacin, doxycycline, erythromycin, gentamicin, levofloxacin, linezolid and vancomycin.