Genetic Investigation of Beta-Lactam Associated Antibiotic Resistance Among Escherichia Coli Strains Isolated from Water Sources.

Background: Antimicrobial resistance is an important factor threatening human health. It is widely accepted that antibiotic resistant bacteria such as Escherichia coli ( E. coli) released from humans and animals into the water sources, can introduce their resistance genes into the natural bacterial community.
Objective: The aim of this study was to investigate the prevalence of bla _TEM , bla _CTX , bla _SHV , bla _OXA and bla _VEB associated-antibiotic resistance among E. coli bacteria isolated from different water resources in Iran.
Methods: The study contained all E. coli strains segregated from different surface water sources. The Kirby-Bauer method and combined discs method was determined in this study for testing antimicrobial susceptibility and strains that produced Extended-Spectrum Beta Lactamases (ESBL), respectively. DNA extraction kit was applied for genomic and plasmid DNA derivation. Finally the frequency of resistant genes including bla _TEM , bla _CTX , bla _SHV , bla _OXA and bla _VEB in ESBL producing isolates were studied by PCR.
Results: One hundred E. coli strains were isolated and entered in the study. The highest antibiotic resistance was observed on clindamycin (96%). Moreover, 38.5% isolates were ESBL producers. The frequency of different ESBLs genes were 37%, 27%, 27%, and 25% for bla _TEM , bla _CTX , bla _SHV , and bla _OXA , respectively. The bla _VEB wasn't found in any isolates.
Conclusion: The study revealed a high prevalence of CTX-M, TEM, SHV and OXA genes among E. coli strains in surface water resources. In conclusion, these results raised a concern regarding the presence and distribution of these threatening factors in surface water sources and its subsequent outcomes.