Ecological and Public Health Implications of the Discharge of Multidrug-Resistant Bacteria and Physicochemical Contaminants from Treated Wastewater Effluents in the Eastern Cape, South Africa

Abstract

This study assessed the prevalence of fecal indicator bacteria (FIB) and Vibrio species, as well as the physicochemical qualities of the discharged effluents of two wastewater treatment facilities, in the Eastern Cape, South Africa over a one-year sampling period using standard methods. Bacteriological assessment revealed presumptive E. coli counts ranging from 3 to 1.2 × 10 5 CFU/100 mL, while counts of Vibrio spp. ranged from 11 to 1.4 × 10 4 CFU/100 mL. Molecular identification of the isolates by polymerase chain reactions (PCR) yielded positive reaction rates of 76.2% (381/500) and 69.8% (279/400) for E. coli and Vibrio species, respectively. The antibiotic susceptibility profiles of 205 randomly selected PCR-confirmed Vibrio isolates against 18 antibiotics revealed resistance frequencies ranging from 0.5% (imipenem) to 96.1% (penicillin G), based on recommended breakpoint concentrations. About 81% (166/205) of the Vibrio isolates exhibited multidrug resistance (resistance to three or more classes of antibiotics), while nine different antibiotic resistance genes were detected by PCR. The physicochemical qualities of the effluents also ranged as follows: pH (6.5-7.6), temperature (12-27 • C), turbidity (1.5-65.7 mg/L), total dissolved solids (95-171 mg/L), dissolved oxygen (2.1-9.8), electrical conductivity (134-267 µS/cm), free chlorine (0.08-0.72 mg/L), biochemical oxygen demand (0.12-9.81 mg/L), nitrate (1.04-21.5 mg/L), nitrite (0.11-0.76 mg/L), phosphate (1.03-18.3 mg/L) and chemical oxygen demand (27-680 mg/L). The discharged effluents fell short of the regulatory guidelines for some of the parameters assessed. We conclude that the discharged effluents are potential sources of environmental pollution and can contribute to drug resistant bacteria load in the receiving watershed, with the associated ecological and human health risks.

Preharvest Transmission Routes of Fresh Produce Associated Bacterial Pathogens with Outbreak Potentials: A Review

“…For instance, the bacteriological assessment of the effluents of two wastewater treatment facilities in South Africa revealed a high count of E. coli (3 to 1.2 × 10 5 Colony Forming Unit (CFU)/100 mL) and Vibrio spp. (11 to 1.4 × 10 4 CFU/100 mL) [99]. However, adequate treatment of wastewater is only done in a few cases because the procedure is costly and time overwhelming [98].…”

Isolation and Characterization of Bacteria from Sewage and Pond Water, Malda, India

“…Thus, this is imperative for the regular vigilance of such wastewater bacteria in order to combat the bacterial multiple antibiotic resistances. for determining the level of antibiotic pollution in the given ecological niches [11,12]. In our earlier report, a high range of MAR indices among gram-negative and gram-positive bacteria, from environmental sources, have been demonstrated [13].…”

“…The isolated bacteria were subjected to the susceptibility test- The MAR indices for the isolated sewage wastewater bacteria were calculated following the formula published earlier [13] and the results were interpreted following the criteria of Krumperman [11]. The antibiotic resistance phenotypes were determined, for the isolates, according to Adefisoye and Okoh [12]; the isolates with resistance to ≥ 3 test antibiotics expressed multiple antibiotic resistance phenotypes.…”

Principal component analysis exploring the association between antibiotic resistance and heavy metal tolerance of plasmid-bearing sewage wastewater bacteria of clinical relevance

“…Incubation was performed at 37 °C, for 24 h, and the results, in terms of zone diameter of inhibition (ZDI; nearest whole in millimetres) from the test antibiotic action, were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) criteria [ 15 ]. The MAR indices for the isolated bacteria were calculated using the formula stated earlier [ 16 ], and MAR phenotype profiles were generated for the isolates with resistance to three or more test antibiotics [ 17 ]. MAR indices of >0.2 indicated that the bacteria originated from niches with a high risk of antibiotic pollution [ 18 ], while MAR indices of >0.4 indicated that the bacterial originated from niches with human faecal contamination [ 19, 20 ].…”