Prevalence of Antibiotic Resistance in Drinking Water Treatment and Distribution Systems

Abstract

The occurrence and spread of antibiotic-resistant bacteria (ARB) are pressing public health problems worldwide, and aquatic ecosystems are a recognized reservoir for ARB. We used culture-dependent methods and quantitative molecular techniques to detect and quantify ARB and antibiotic resistance genes (ARGs) in source waters, drinking water treatment plants, and tap water from several cities in Michigan and Ohio. We found ARGs and heterotrophic ARB in all finished water and tap water tested, although the amounts were small. The quantities of most ARGs were greater in tap water than in finished water and source water. In general, the levels of bacteria were higher in source water than in tap water, and the levels of ARB were higher in tap water than in finished water, indicating that there was regrowth of bacteria in drinking water distribution systems. Elevated resistance to some antibiotics was observed during water treatment and in tap water. Water treatment might increase the antibiotic resistance of surviving bacteria, and water distribution systems may serve as an important reservoir for the spread of antibiotic resistance to opportunistic pathogens.The occurrence and spread of antibiotic-resistant bacteria (ARB) are pressing public health problems worldwide, and aquatic ecosystems are a recognized reservoir for ARB and antibiotic resistance genes (ARGs) (4,6,8,11,12,15,39). Naturally occurring ARB and ARGs in the aquatic environment are selected for and enriched for by antibiotics found in sewage and agricultural runoff, which result from the widespread and increased use of antibiotics (4,11,12,15,38). Historically, concerns about the microbial quality of drinking water have focused on the occurrence of pathogens in drinking water distribution systems (5, 34). However, the presence of trace levels of antibiotics and ARB in source water and finished drinking water may also greatly affect public health and is an emerging issue for the general public and the drinking water industry (3,30). Although several studies have detected ARB in drinking water systems (2,3,20,30,38), most previous studies focused on cultivable bacteria and/or indicator organisms. Little is known about the fate of ARGs in drinking water systems, and it was recently proposed that ARGs are emerging contaminants (24).We used culture-dependent methods and molecular techniques to investigate the prevalence and dynamics of heterotrophic ARB and ARGs in a drinking water source (source RW-P) and treated drinking water (source DW-P) (see Materials and Methods in the supplemental material). We tested water from a drinking water plant located in Michigan and tap water from several small cities located in Michigan and Ohio (sources TW-1, TW-2, TW-3, and TW-4). Two independent samples were collected each time at each collection site at three different times, and we used four replicates from each sample for tests. We tested bacterial resistance to the following antibiotics: amoxicillin (amoxicilline), chloramphenicol, ciprofloxacin, gentamicin, rifampi...

Tertiary-Treated Municipal Wastewater is a Significant Point Source of Antibiotic Resistance Genes into Duluth-Superior Harbor

“…Bacterial biomass in the different surface water samples varied substantially from as high as 3.6 × 10 6 gene copies per mL (sample location = SLR2) to as low as 2.1 × 10 5 gene copies per mL (sample location = LS2). These quantifications of 16S rRNA gene copies are substantially lower than that previously reported from the Haihe River in China (10 8 -10 9 copies per mL) 37 and from a drinking water source in Michigan (3.4 × 10 9 copies per mL), 38 but are consistent with previously reported direct cell counts from Lake Superior (1 × 10 5 cells/mL). 25 The quantity of bacterial biomass in the treated WLSSD effluent was 5.4 × 10 6 gene copies per mL, which was higher than any surface water sample.…”

Antibiotic resistance in urban aquatic environments: can it be controlled?

“…In addition, also some well-known acquired antibiotic resistance determinants, often associated with mobile genetic elements, have been reported in drinking water using culture-independent methods. Genes such as vanA, blaTEM, sul1, or intI1 (related with vancomycin, beta-lactam and sulfonamides resistance, and class 1 integrons, respectively) have been detected, although at very low abundance, in biofilm or planktonic DNA of tap water samples that fulfilled the quality criteria in different world regions (Schwartz et al 2003;Xi et al 2009; our data unpublished). The risks associated with intrinsic or acquired antibiotic resistance in drinking water for the dissemination of antibiotic resistance and its transmission to humans are not known; however, this is an issue that seems to deserve additional research.…”

TTC- Based Test as an Efficient Method to Determine Antibiofilm Activity of Silver Nanoparticles

“…Microorganisms resistant to antibiotics in water distribution system also exhibit resistance to chlorination. Environmental stress caused by the disinfection process may consequently increase the resistance to antibiotics [25]. Biofilm forming microorganisms are far more resistant to environmental stress, thus the first selection emerged microorganism whose high ability for adhesion and simultaneous resistance to antibiotics, which confirms the direct descent of biofilm.…”