ABSTRACT
The emergence of antimicrobial-resistant genes and the indiscriminate use of antibiotics contribute to the dissemination of resistant pathogens in the environment. The objective of the present study was isolation and molecular identification of antibiotic resistant bacteria from the hospital sewage and investigation of the role of plasmid in resistance mechanism. In this experimental study, the antibiotic resistance patterns of the isolated strains from hospital effluent samples were assayed by disc diffusion method. The selected isolate was identified by morphological and biochemical methods in accordance with Bergey's Manual of Systematic Bacteriology. Phylogenetic analysis was performed based on 16S rRNA gene sequences. Plasmid extraction was carried out by alkaline lysis technique and curing of plasmids performed by Ethidium bromide. Ten bacterial strains were isolated from hospital sewage. Results of antibiotic susceptibility test showed that all of the isolates were multi-drug resistant. One of the isolates [ST1] was resistant to all of the tested antibiotics. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belongs to the genus Acinetobacter then designated as Acinetobacter sp. HM_C. Phylogenetically the closest relative of strain was Acinetobacter baumanni IARI-V-4. Curing experiments by Ethidium bromide caused the elimination of all plasmids. The sensitivity of the plasmid cured ST1 to gentamycin, and amikacin indicated that the genes encoding resistance to gentamycin, and amikacin were located on plasmid. Hospital effluents are important materials in dissemination of multidrug resistant bacteria and their resistant genes into the environment