Original articleQuantitation of antibiotic resistance genes pollution in hospital waste water effluent and Urban Clinton River Water, Michigan, USA
Introduction
The discharge of municipal, domestic, industrial, hospital waste water effluent containing antibiotics and antibiotic-resistant bacteria in great lakes and rivers has raised serious health concerns2 and considerable efforts are directed toward evaluation, control and prevention of municipal discharges into Great Lakes Water Bodies, in Michigan, USA.3 Antibiotics are used for aqua culture, animal husbandry and most importantly for the treatment of life-threatening bacterial infections in humans.4, 5, 6 Significant amounts of biologically active antibiotics are released in water bodies via agricultural farming, aqua culture overflow, effluent from hospital sewage treatment plant and municipal waste-water treatment plant.5, 7 Municipal wastewater and surface waters, being receptors of gut microbiota of humans and other animals, constitute important vehicles in the dissemination of resistant pathogenic bacteria in water environment.8 Recent studies indicate incomplete elimination and release of antibiotic-resistant bacteria to effluent receiving streams.9 Antibiotics may act as signaling compounds at sub-inhibitory concentrations and select for antibiotic-resistant bacteria. Although inputs of antibiotic-resistant bacteria and antibiotics to streams have been reported, it is not clear whether or to what extent inputs of low-levels of antibiotics from waste-water treatment plants (WWTPs) affects antibiotic resistance among effluent bacteria after entry into the receiving stream.
Of major concern is the diversity of extended-spectrum beta-lactamases (ESBLs) producing bacteria into the environment which is resistant to the third and fourth-generation cephalosporins, aminogycosides, quinolones, etc. The bacteria confer resistance to the antibiotics, mainly due to the production of beta-lactamase enzyme thus inactivating the beta-lactam ring of the antibiotic.10 Many of these organisms harbor antibiotic-resistance genes, eventually inserted into genetic mobile platforms (plasmids, transposons, integrons) able to spread among water and soil bacterial communities.11, 12 Water constitutes not only a way of dissemination of antibiotic-resistant organisms among human and animal populations, as drinking water is produced from surface water, but also the route by which resistance genes are introduced in natural bacterial ecosystems.13 In such systems, nonpathogenic bacteria could serve as a reservoir of resistance genes and platforms. Moreover, the introduction and progressive accumulation of chemical of emerging concerns (CEC, antimicrobial agents, detergents, disinfectants, and residues from industrial pollution, as heavy metals), in the environment of CEC contributes to the evolution and spread of such resistant organisms in the water environment.13, 14, 15 The objective of this study is to determine occurrence of antibiotic-resistant bacteria (ARB) in the hospital waste water effluent discharged in receiving streams and their potential health effect on human life. The preliminary results of this study were presented at American Society for Microbiology (ASM) Microbe 2016 (Boston, MA, USA).
Section snippets
Bacteriological and molecular analysis of waste water samples
Two waste water samples from the William Beaumont Hospital (Royal Oak, MI, USA) were collected. One sample was taken from the from the north east side of hospital waste water discharge point connecting to sewage line, and the other sample was collected from northwest side of the hospital before entering the hospital. The recreational Urban Clinton River Water (UCRW, Rochester, MI, USA) was used as a control to the hospital effluent with the assumption that it will contain the low amount of
Results
A total of 156 bacteria were isolated from effluent, downstream and upstream of the hospital waste-water treatment plant. Antibiotic susceptibility was determined for these bacteria as shown in Fig. 1. The bacteria isolated from the two sites (upstream and downstream of William Beaumont Hospital) were approximately 40–65% resistant to cefotaxime, 25–40% to chloramphenicol, 30–40% to tetracycline, 25–65% to ciprofloxacin and finally 30–50% to gentamicin. Of all cultivable bacteria, 34 (22%) were
Discussion
Human exposure to antibiotic-resistant bacteria (ARB) is a public health concern as it has direct links with disease management. This exposure could occur in a number of ways. Hospital and urban rivers seem to play an important role in the dissemination of ARB and antibiotic-resistant genes (ARG) in the environment. Earlier studies have shown that hospital effluent discharge without prior treatment is responsible for dissemination of ARG to environment (rivers, lakes, and seas).17 In contrast,
Conclusions
Hospital effluent and urban rivers are potential source and routes for the dissemination of ESBL producing bacteria and their genes into the natural environment. This could pose a hazard to environmental and public health.
Conflicts of interest
The authors have none to declare.
Acknowledgements
The authors are very grateful to William Beaumont Hospital Waste Water plant personnel for their assistance in the collection of hospital effluent samples. We are also grateful to Manhar Swani for the β-lactamase identification and Dipanshu Walia for his assistance in the preparation of the study material for this investigation.
References (20)
- et al.
Characterization of integrons and tetracycline resistance determinants in Aeromonas spp. isolated from South African aquaculture systems
Int J Food Microbiol
(2007) - et al.
Antibiotics and antibiotic resistance in water environments
Curr Opin Biotechnol
(2008) - et al.
Understanding the mechanisms and drivers of antimicrobial resistance
Lancet
(2016) - et al.
Evaluating the vulnerability of surface waters to antibiotic contamination from varying wastewater treatment plant discharges
Environ Pollut
(2006) - et al.
Vancomycin resistant Enterococci: from the hospital effluent to the urban wastewater treatment plant
Sci Total Environ
(2013) - et al.
Concentration-dependent activity of antibiotics in natural environments
Front Microbiol
(2013) - et al.
Wastewater as a point source of antibiotic-resistance genes in the sediment of a freshwater lake
ISME J
(2014) - et al.
Occurrence of virulence and antimicrobial resistance genes in Escherichia coli isolates from different aquatic ecosystems within the St. Clair River and Detroit River areas
Appl Environ Microbiol
(2007) - et al.
Tackling antibiotic resistance: the environmental framework
Nat Rev Microbiol
(2015) - et al.
Novel method for rapid assessment of antibiotic resistance in Escherichia coli isolates from environmental waters by use of a modified chromogenic agar
Appl Environ Microbiol
(2007)