This study investigated the prevalence of antibiotic-resistant bacteria and genes in fecal sludge and soil in Ho Chi Minh City, Vietnam, and identified the factors contributing to the survival of antibiotic-resistant bacteria in soil. Sludge and soil samples (n = 24 and 55, respectively) were collected from residential septic systems and environmental reservoirs (i.e., canals, rivers, and parks) in twelve districts of Ho Chi Minh City and tested against a library of 12 antibiotic-resistant genes and 1 integron gene. The susceptibility of isolated Escherichia coli from sludge and soil (n = 104 and 129, respectively) was tested against nine antibiotics. Over 60% of sludge and soil samples harbored sul1, ere(A), intI1, cmIA, and tet(A) genes. The three most common phenotypic resistances found in E. coli isolated from sludge and soil were to ampicillin, tetracycline, and sulfamethoxazole/trimethoprim. In a temporal microcosm study of antibiotic-susceptible and multi-drug-resistant E. coli inoculated in soil, temperature (21.4 vs. 30 °C), resistance phenotype, and soil background microbial community were associated with E. coli decay rates over 73 days. This is the first study that provides insights into the high prevalence of antibiotic resistance in septic systems and environmental reservoirs in Ho Chi Minh City, Vietnam. Findings highlight that the fecal sludge and soil environments in Vietnam are likely reservoirs for dissemination of and human exposure to antibiotic resistance.
Keywords: Antibiotic-resistant bacteria; Antibiotic-resistant genes; E. coli; Fecal sludge; Soil; Vietnam.