Original article
Quantitation of antibiotic resistance genes pollution in hospital waste water effluent and Urban Clinton River Water, Michigan, USA

https://doi.org/10.1016/j.cmrp.2016.07.005Get rights and content

Abstract

Hospitals are the major antibiotic consumers and thus facilitate the spread of antibiotic resistance. Hospital wastewaters definitely play an important role in the evolution and dissemination of antibiotic-resistant genes. In this study, we evaluated the occurrence of three common groups of extended spectrum beta lactamase (ESBL) and their resistance genes in the hospital effluent and urban river as possible sources. A total of 156 bacteria were isolated from upstream and downstream of hospital waste-water treatment plant. Waste water samples were analyzed for the copy number of three groups of ESBL; SHV, TEM and CTX-M-1 genes. The bacteria isolated 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 these 156 bacteria, 34 (22%) were found to be ESBL producing bacteria. The copy numbers1 are 102, 104 and 103, respectively. Based on the data, the abundance of blaSHV and blaCTX-M-1 remained similar in both populations whereas the quantity of blaTEM decreased to an order of 102 in Urban Clinton River Water (UCRW). Hospital effluent and urban rivers are potential routes for dissemination of ESBL producing bacteria and their respective genes into the natural environment and pose a hazard to environmental and public health.

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.

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