en میکروب شناسی محیطی - صنعتی Environmental Microbiology مقاله پژوهشی Original Research Article <p style="text-align: justify;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Background and Aim:</span></span></span></b><span style="color:black"> This study investigated the prevalence of antibiotic-resistant <i>Escherichia coli</i> in untreated and treated wastewater from a hospital wastewater treatment system and assessed their persistence after chlorine disinfection.</span><span lang="EN-ID"><span style="color:black"></span></span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Materials and Methods:</span></span></span></b><span style="color:black"> The study included three main steps. First, <i>E. coli</i> was isolated from untreated and treated wastewater samples. Second, antibiotic susceptibility was assessed phenotypically. Ten antibiotics were tested using the Kirby&ndash;Bauer disk diffusion method, while colistin susceptibility was evaluated by broth microdilution to determine the minimum inhibitory concentration (MIC). Colistin results were interpreted according to the EUCAST breakpoint for Enterobacterales, with MIC &le;2 mg/L considered susceptible and MIC >2 mg/L considered resistant. Third, selected resistance genes related to ESBL production, colistin resistance, and carbapenem resistance were detected by PCR after thermal DNA extraction.</span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Results:</span></span></span></b><span style="color:black"> <i>Escherichia coli</i> was detected in 5 of 10 untreated wastewater samples (50.0%) and 6 of 10 treated wastewater samples (60.0%), with no statistically significant difference (p > 0.05). Because the sample size was small and more than one isolate was obtained from some samples, the results should be interpreted as detection-frequency data rather than evidence of bacterial-load reduction. Ampicillin resistance was the most common phenotype in untreated wastewater isolates (86.7%) and was detected in all treated wastewater isolates (100%). Fosfomycin resistance was the least common phenotype in treated wastewater isolates (5.6%). The genes <i>bla</i>TEM, <i>bla</i>CTX-M-1 group, <i>bla</i>CTX-M-9 group, and <i>mcr</i>-1 were detected in isolates from both wastewater types, while selected carbapenemase genes were detected in treated-wastewater isolates.</span><br> <b><span style="background:#1f497d"><span style="color:white"><span style="letter-spacing:-.1pt">Conclusion:</span></span></span></b><span style="color:black"> The treatment system reduced conventional physicochemical pollutants but did not fully remove detectable antibiotic-resistant <i>E. coli</i> or selected resistance genes.</span></span></span></p> Escherichia coli, Antibiotic Resistance Genes, Hospital Wastewater, Chlorination, Antimicrobial Resistance 31 46 http://ijmm.ir/browse.php?a_code=A-10-3028-4&slc_lang=en&sid=1 Thanh Phong Ngo ngothanhphong@iph.org.vn 100319475328460034281 0009-0003-4382-6945 No Institute of Food and Biotechnology, Can Tho University, Can Tho City, Viet Nam Xuan Phong Huynh hxphong@ctu.edu.vn 100319475328460034282 100319475328460034282 No Institute of Food and Biotechnology, Can Tho University, Can Tho City, Viet Nam Van Chinh Dang dangvanchinh@iph.org.vn 100319475328460034283 100319475328460034283 No Institute of Public Health in Ho Chi Minh City, Ho Chi Minh City, Viet Nam Long Ho Phan phanlongho@iph.org.vn 100319475328460034284 100319475328460034284 No Institute of Public Health in Ho Chi Minh City, Ho Chi Minh City, Viet Nam Trung Tri Le letrungtribvsd@gmail.com 100319475328460034285 100319475328460034285 No Sa Dec General Hospital, Dong Thap Province, Viet Nam Do Hung Tran tdhung@ctump.edu.vn 100319475328460034286 100319475328460034286 Yes Department of Medicine and Pharmacy, Can Tho University, Can Tho City, Viet Nam