Abstract
In disenfranchised communities, untreated greywater (wastewater without sewage) is often environmentally discharged, resulting in potential human exposure to antimicrobial-resistant bacteria (ARB), including extended-spectrum beta-lactamase (ESBL) producers. We sought to examine the abundance of ARB, specifically ESBLs, and antimicrobial resistance genes (ARGs) in greywater from off-grid, pastoral Bedouin villages in Southern Israel. Greywater samples (n = 21) collected from five villages were analyzed to enumerate fecal coliforms and Escherichia coli. ESBL producers were recovered on CHROMagar ESBL and confirmed by VITEK®2 (bioMerieux, Marcy l’Etoile, France) for identification and antimicrobial susceptibility testing. Total genomic DNA was extracted from greywater samples and quantitative PCR (qPCR) was used to determine relative abundance (gene copies/16S rRNA gene) of class 1 integron-integrase intI1, blaTEM, blaCTX-M-32, sul1, and qnrS. The mean count of presumptive ESBL-producing isolates was 4.5 × 106 CFU/100 mL. Of 81 presumptive isolates, 15 ESBL producers were recovered. Phenotypically, 86.7% of ESBL producers were multi-drug resistant. Results from qPCR revealed a high abundance of intI1 (1.4 × 10−1 gene copies/16S rRNA), sul1 (5.2 × 10−2 gene copies/16S rRNA), and qnrS (1.7 × 10−2 gene copies/16S rRNA) followed by blaTEM (3.5 × 10−3 gene copies/16S rRNA) and blaCTX-M-32 (2.2 × 10−5 gene copies/16S rRNA). Results from our study indicate that greywater can be a source of ARB, including ESBL producers, in settings characterized by low sanitary conditions and inadequate wastewater management.
Highlights
Increase in levels of antimicrobial-resistant bacteria (ARB) [1] and antimicrobial resistance genes (ARGs) in the environment due to the discharge of wastewater is a recent human health concern.Water 2020, 12, 1460; doi:10.3390/w12051460 www.mdpi.com/journal/waterUntreated greywater (GW, wastewater from all household sources other than sewage) is known to harbor pathogens including but not limited to Klebsiella pneumoniae, Pseudomonas aeruginosa, and Legionella sp. [2,3,4]
Our results demonstrate that untreated GW can harbor ARB and ARGs of human origin, and this is one of the first studies reporting the presence of MDR extended-spectrum beta-lactamase (ESBL)-producing bacteria in untreated GW discharged from household activities
The current findings from our study indicate that untreated GW can serve as a potential source of ARGs and MDR bacteria such as Gram-negative ESBL producers
Summary
Increase in levels of antimicrobial-resistant bacteria (ARB) [1] and antimicrobial resistance genes (ARGs) in the environment due to the discharge of wastewater is a recent human health concern.Water 2020, 12, 1460; doi:10.3390/w12051460 www.mdpi.com/journal/waterUntreated greywater (GW, wastewater from all household sources other than sewage) is known to harbor pathogens including but not limited to Klebsiella pneumoniae, Pseudomonas aeruginosa, and Legionella sp. [2,3,4]. GW has been identified as a potential factor responsible for proliferation of resistant bacteria [5,6,7]. Factors such as crowding, poor sanitation, and antimicrobial misuse are known drivers of antimicrobial resistance (AMR) among low socioeconomic status populations [8]. Despite these known concerns, the risks of potential human exposure to AMR in the case of disenfranchised communities where domestic GW is often environmentally discharged without treatment is understudied.
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