Emergence of ciprofloxacin-resistant extended-spectrum β-lactamase-producing enteric bacteria in hospital wastewater and clinical sources

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Highlights

  • The study reports a common prevalence of ESBL-producing enteric bacteria in clinical and hospital wastewater which is a matter of great public health concern.

  • A close association of ciprofloxacin resistance with ESBL production was found indicating an emergence of hazardous trends of MDR combinations of resistance among enteric bacteria.

Abstract

This study aimed to evaluate the incidence of ciprofloxacin-resistant extended-spectrum β-lactamase (ESBL)-producing enteric bacteria in hospital wastewater and clinical sources. Enteric bacteria, mainly Escherichia coli, were isolated from clinical sources (urinary tract and gastrointestinal tract infections; 80 isolates) and hospital wastewater (103 isolates). The antibiotic resistance profile and ESBL production of the isolates were investigated by disc diffusion assay and combined disc diffusion test, respectively. Plasmid profiling was performed by agarose gel electrophoresis, and elimination of resistance markers was performed by a plasmid curing experiment. Antibiotic susceptibility testing revealed a high incidence of β-lactam resistance, being highest to ampicillin (88.0%) followed by amoxicillin, ceftriaxone, cefpodoxime, cefotaxime, aztreonam, cefepime and ceftazidime. Among the non-β-lactam antibiotics, the highest resistance was recorded to nalidixic acid (85.7%). Moreover, 50.8% of enteric bacteria showed resistance to ciprofloxacin. Among 183 total enteric bacteria, 150 (82.0%) exhibited multidrug resistance. ESBL production was detected in 78 isolates (42.6%). A significantly higher incidence of ciprofloxacin resistance was observed among ESBL-producing enteric bacteria both in clinical (P = 0.0015) and environmental isolates (P = 0.012), clearly demonstrating a close association between ESBL production and ciprofloxacin resistance. Plasmid profiling of selected ESBL-positive strains indicated the presence of one or more plasmids of varying sizes. Plasmid curing resulted in loss of ciprofloxacin and cefotaxime resistance markers simultaneously from selected ESBL-positive isolates, indicating the close relationship of these markers. This study revealed a common occurrence of ciprofloxacin-resistant ESBL-producing enteric bacteria both in hospital wastewater and clinical sources, indicating a potential public health threat.

Introduction

Hospital wastewater is considered one of the major reservoirs of pathogenic bacteria. Wastewater or natural water supplies into which wastewater has been discharged are likely to contain pathogenic organisms mainly coming from human excreta [1]. Furthermore, antibiotics used in hospitals and their release into effluents and municipal sewage via patient excreta or direct deposition impose a selection pressure on bacteria leading to emergence of resistance to different classes of antibiotics in micro-organisms in the aquatic environment [2]. Besides this, wastewater from hospitals constitutes a route of dissemination of antibiotic-resistant bacteria to human and animal populations through various ecological modes of transmission including food, water and insects vectors. Moreover, in developing countries, the chance of transmission of pathogenic bacteria is more common owing to lack of adequate hygiene, poor water quality and inadequate management of human and hospital wastes [1]. Considering the impact of hospital-acquired infections, national evidence-based guidelines for preventing healthcare-associated infections in National Health Service (NHS) hospitals were commissioned by the Department of Health in England. These guidelines focused on hospital environmental hygiene, hand hygiene, the use of personal protective equipment, and the safe use and disposal of sharps; preventing infections associated with the use of short-term indwelling urethral catheters; and preventing infections associated with central venous catheters [3].

The occurrence of drug-resistant micro-organisms in hospital wastewater and clinical sources creates immense clinical and public health problems. Currently, extended-spectrum β-lactamase (ESBL)-producing enteric bacteria are globally recognised problematic multidrug-resistant (MDR) bacteria. ESBLs confer resistance to β-lactam antibiotics containing an oxyimino group (e.g. ceftazidime, cefotaxime and aztreonam). ESBL-producing organisms have been associated with various community- and hospital-acquired infections, including urinary tract infections, bacteraemia, peritonitis, nosocomial pneumonia, intra-abdominal infections and meningitis [4]. Ciprofloxacin has been regarded as a potent antimicrobial recommended for the treatment of various diseases caused by ESBL-producing enteric bacteria [4], [5]. As the use of fluoroquinolones in treatment strategies is increasing, resistance to fluoroquinolones has emerged and has been documented globally. A recent surveillance study, the Study for Monitoring Antimicrobial Resistance Trends (SMART), included 38 hospitals from 10 countries in the Asia-Pacific region and found 48.6% resistance to ciprofloxacin with wide variation among different countries, being as high as 76.2% in Vietnam and 72.0% in China [6].

However, the incidence of fluoroquinolone resistance in ESBL-producing enteric bacteria is less explored in India [7]. Therefore, the aim of this study was to investigate the prevalence of ciprofloxacin resistance and ESBL production among enteric bacteria from hospital wastewater as well as clinical sources and to emphasise the impact of this potential problem on human health.

Section snippets

Isolation and characterisation of enteric bacteria and growth conditions

Enteric bacteria from clinical sources were isolated from urine samples of patients with urinary tract infection and from stool samples of patients with gastrointestinal tract infection (mainly diarrhoea) at Jawaharlal Nehru Medical College, Aligarh Muslim University (Aligarh, India) and Ashok Pathology and Research Centre (Aligarh, India). Wastewater samples were collected from the Jawaharlal Nehru Medical College Hospital wastewater discharging point during the months December 2011 to

Results

A total of 183 isolates comprising E. coli (n = 101), K. pneumoniae (n = 17), Enterobacter spp. (n = 21), Salmonella spp. (n = 18), Shigella spp. (n = 9) and Proteus spp. (n = 17) were isolated, of which 80 were from clinical sources and 103 were isolated from hospital wastewater (Supplementary Table S1).

. Details of enteric bacteria isolated from different sources.

The incidence of antibiotic resistance against individual antibiotics was determined for 16 antibacterial agents. Overall, the bacterial isolates

Discussion

The prevalence of antibiotic resistance among bacteria has been increasing in recent years. In this study, a greater incidence of resistance to antibiotics and the MDR nature of the test isolates revealed that there was a continuous selective pressure of commonly used antibiotics in the hospital environment. Moreover, non-antibiotic toxic compounds in the environment may also help in the development and selection of co-resistance to antibiotics [13].

Production of ESBL is the most prevalent

Funding

MM has received financial assistance from Aligarh Muslim University (Aligarh, India) in the form of a non-NET-UGC Fellowship of the University Grants Commission.

Competing interests

None declared.

Ethical approval

Not required.

Acknowledgments

The authors are grateful to Prof. Abida Malik (Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh, India) and Dr Ashok Kumar (Ashok Pathology and Research Centre, Aligarh, India) for providing the clinical isolates.

References (16)

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