Assessment of antibiotic- and disinfectant-resistant bacteria in hospital wastewater, south Ethiopia: a cross-sectional study

Abstract

Introduction: Large quantities of antimicrobials are used in hospitals for patient care and disinfection. Antibiotics are partially metabolized and residual quantities reach hospital wastewater, exposing bacteria to a wide range of biocides that could act as selective pressure for the development of resistance. Methodology: A cross-sectional study was conducted between December 2010 and February 2011 on hospital wastewater. A total of 24 composite samples were collected on a weekly basis for bacteriological analysis and susceptibility testing. Indicator organisms and pathogenic and potentially pathogenic bacteria were found and isolated on selective bacteriologic media. Disinfectant activity was evaluated by use-dilution, and minimum inhibitory concentration (MIC) was determined by the agar dilution method. Similarly, antibiotic susceptibility tests were performed using the Kirby-Bauer disk diffusion method. Results: Pathogenic (Salmonella, Shigella, and S. aureus) and potentially pathogenic (E. coli) bacteria were detected from effluents of both hospitals. Dilution demonstrated tincture iodine to be the most effective agent, followed by sodium hypochlorite; the least active was 70% ethanol. MIC for ethanol against S. aureus and Gram-negative rods from Yirgalem Hospital (YAH) showed 4 and 3.5 log reduction, respectively. Salmonella isolates from YAH effluent were resistant to ceftriaxone, tetracycline, and doxycycline. Isolates from Hawassa University Referral Hospital (HURH) effluent were resistant to the above three antibiotics as well as gentamycin. Conclusions: Hospital effluents tested contained antibiotic-resistant bacteria, which are released into receiving water bodies, resulting in a threat to public health.

Identification of antibiotic-resistant Escherichia coli isolated from a municipal wastewater treatment plant

“…When the number of bacterial colonies was too high to be counted, the wastewater samples were diluted in Ca 2þ -free and Mg 2e -free phosphate buffered saline by 10 À2 to 10 À4 to have a reliable colony number. Since green colonies can be mostly ascribed to b-glucoronidase-positive Enterobacteria, and E. coli is by far the prevalentone compared to Salmonella and Shigella (Fekadu et al, 2015), the latter-ones were not taken into consideration. Considering the EUCAST breakpoint tables, that classify Enterobacteria as AMP R and CAF R when the MIC is >8 mg/mL (The European Committee on Antimicrobial Susceptibility Testing, 2016; Choffnes et al, 2011), the E. coli colonies were grown in agar medium where increasing AMP and CAF concentrations had been added (0, 8, 16, 32 mg/mL; Sigma, St Louis, MO, USA), to selectively monitor and count the resulting AMP R and CAF R colonies.…”

Antibiotic Resistant Bacteria from Treated and Untreated Hospital Wastewater at Ayder Referral Hospital, Mekelle, North Ethiopia

“…The same study conducted in Ethiopia, Hawassa University Referral Hospital, reported Salmonella spp, Shigella spp, E. coli and S. aureus from hospital effluent [3]. Similarly, from Thailand pathogenic bacteria like Vibrio spp and Salmonella spp as well as other potentially pathogenic bacteria were reported [23].…”

“…It carries the resistant bacteria introduced into the sewage system that come from human excretions, liquid waste discharged from domestic home, agricultural and commercial sectors, pharmaceutical and hospitals [2] [3].…”

Microbiological Quality of the Effluents Produced by the University and Hospital Centres in the Department of Littoral, Republic of Benin

“…The same results were reported in the study conducted by Asfaw et al in Ethiopia [24]. In addition, a study conducted at Hawassa University Reference Hospital, reported the presence of Salmonella spp., Shigella spp., E. coli and S. aureus in hospital effluents [25].…”