Discharge Of Antibiotic-Resistant Bacteria From Urban Waste Treatment Facilities

ABSTRACT:Since the first clinical use of penicillin for microbial infection treatment in1940s, antibiotics have made an enormous contribution to human health-care and disease prevention. However, the abuse of antibiotic drugs has led to the accelerated emergence of antibiotic resistant genes (ARGs) and wide-spread of antibiotic resistant bacteria (ARBs), while poses a serious threat to the health of man-kind.The ARBs discharged from urban waste treatment facilities, such as wastewater treatment and solid-wastes management and disposal plants, could find their ways into the aquatic environment. From the perspectives of water environment protection and water usage safety, the characterization of the occurrence and discharge patterns of ARBs from these urban waste treatment facilities is of great importance. To this end, the present thesis investigated the antibiotic resistance properties of the E. coli strains isolated from a wastewater treatment plant, municipial solid waste transfer stations and landfill leachates.The results indicate that the number of culturable bacteria in leachates sampled from solid waste transfer stations and landfill sites is higher than107cell/ml, while the ARBs concentration is in the range of103-104cell/ml, respectively. The culturable bacterial cells in the surface water closed to a landfill plant is higher than107cell/ml, with the ARBs higher than105cell/ml. We have isolated236strains of E.coli from treated wastewater, solid waste leachate and surface water near the waste treatment facilities. The susceptibility assays of these strains to commonly used18antibiotics were carried out by the disk-diffusion methods according to the procotol recommended by the Clinical and Laboratory Standard Institute. The main conclusions could be drawn as follows:1. All E. coli strains exhibit resistance to more than two kinds of antibiotics tested in the experiments.2. The classifications antibiotics to which E. coli have stronger resistance are glycosides, large cyproterone esters, β-lactam antibiotics, while quinolones, sulfonamides, amphenicols drugs showed higher sensitivity to E. coli strains.3. More than80%E. coli strains are resistant to the antibiotics clinically adopted in1950s-1960s. 4. The antibiotics with highest resistance are vancomycin, erythromycin, amoxicillin, ampicillin, imipenem. On the contrary, ofloxacin, levofloxacin, cefoperazone are the most effective antibiotic drugs.5. Most E. coli strains are multi-resistant, on average resistant to more than5classifications of the antibiotics tested in the study.6. The statistic tests of the antibiotic resistance between the E. coli strains isolated from the landfill leachate and from the surface water nearby indicated that no significant difference exists, which implies the surface water was affected by the landfill plants.