부산대학교 도서관

Among environmental contaminants polychlorinated biphenyls (PCBs) are still a concern due to their persistence in environment. As an emerging contaminant, they are directly linked to climate change and few studies are available for their relation between microbiota including bacteria. Antibiotic resistance (AMR) as an increasing global issue, is still to be debated for its relation with pollutants. This study was aimed to determine the effects of dioxin-like PCB (PCB118) on tetracycline (Tet) resistance in Enterococcus faecalis ATCC 29212. Tet resistant strains were obtained by inducing tetracycline at 2-125 ppm,where the strains were exposed to Tet at increasing concentrations for cumulative 14 days to be transferred from nutrient agar to nutrient broth every day. PCB118 at 100 ppt in isooctane were added to tetracycline resistant strains. 6 groups were studied where bacterial strains in cultured broth of Group 1 received PCB and Tet, Group 2 received isooctane and Tet, Group 3 only Tet, Group 4 only PCB, Group 5 only isooctane and Group 6 broth only as a bacterial control. Antimicrobial susceptibility were determined by Kirby-Bauer disc diffusion and standard broth microdilution method for AMR as defined by CLSI guidelines. All experiments were run in triplicates. Zone diameters were found to be lower (27%, p<0.05) and MIC values were higher (29%, p>0.05) in Group 1 compared to Group 3. Indicating that PCB treated group were more resistant compared to Tet only treated group. MIC results of Group 2 and 5, which both received isooctan, indicate that isooctan only group were more susceptible,where cytotoxic effects of the organic solvent were thought to have influenced in vitro. This is the first study to directly link antibiotic resistance on PCB presence in E. faecalis in vitro. The preliminary experiment indicates that environmental contaminant, PCB118, induce positive effects on tetracycline resistant E. faecalis strains, where resistance were found to be increased. E. faecalis, as an environmental pathogen, where the resistant genes survive though sewage treatment, increase of the viability with respect to PCB polluted areas increase risk for human health. Further in vivo studies revealing the mechanisms of resistance-PCB relation are expected to confirm. [ABSTRACT FROM AUTHOR]