Antibiotic Resistance and Plasmid Profiling of Escherichia coli Isolated from Human Sewage Samples

Abstract

In developing countries, the occurrence of antibiotic resistance is increasing day by day and antibiotic resistant microorganisms are being found in almost every environmental setting. Plasmids are considered as the main vector in the procurement and propagation of antibiotic resistance in many microorganisms such as Escherichia coli (E. coli). The goal of this study was to examine the antibiotic resistance and screening of plasmid in E. coli strains which were previously identified from human sewage samples. During this study antibiotic susceptibility of E. coli isolates were determined by Kirby-Bauer disk diffusion method against 5 antibiotics (ampicilin, ceftriaxone, amoxicillin, ciprofloxacin, azithromycin). Furthermore, plasmid extraction of each isolate was done according to the protocol of FavorPrepTMPlasmid Mini Kit and plasmid profiling was done by agarose gel electrophoresis. In antibiotic sensitivity test, all E. coli strains showed resistance to ampicilin, amoxicillin, and ceftriaxone. In the plasmid profiling, it was revealed that all the isolates of E. coli harbored plasmids. The plasmid sizes ranged from approximately 1.5 to 15 kb. The findings of this study prove the consequences of antibiotic resistance as well as relationship of plasmid with antibiotic resistance which necessitates proper surveillance on antibiotic usage in the developing countries.

Keywords: E. coli; antibiotic resistance; plasmid.

Figure 1.

(A) Antibiotic sensitivity test by Kirby-Bauer Disk diffusion method. Picture of culture plates showed zone of inhibition by Ec-CRS1 and Ec-CRS2 against different antibiotics. (B) A, 1 kb DNA ladder; B, Identification of Plasmid DNA through gel electrophoresis (Lane M= DNA ladder, Lane 1-8 shows band for Ec-CRS1, Ec-CRS2, Ec-JHT3, Ec-AKS4, Ec-AKS5. Ec-AKS6, Ec-KPM7, Ec-KPM8, respectively). Abbreviations: AZM, azithromycin; AMX, amoxicillin; AMP, ampicilin; CIP, ciprofloxacin; CTR, ceftriaxone.