Abstract
Antibiotic resistance of the indicator microorganism Escherichia coli was investigated in isolates from samples collected during the course of one year from two wastewater treatment plants treating municipal and animal wastes in Slovakia, respectively. The genes of antibiotic resistance and virulence factors in selected resistant E. coli isolates were described. A high percentage of the isolates from municipal and animal wastewater were resistant to ampicillin, streptomycin, tetracycline, ceftiofur, ceftriaxone, and enrofloxacin. In the selected E. coli isolates, we detected the following phenotypes: ESBL (20.4% in animal wastewater; 7.7% in municipal wastewater), multidrug-resistant (17% of animal and 32% of municipal isolates), high resistance to quinolones (25% of animal and 48% of municipal samples), and CTX-M (7.9% of animal and 17.3% of municipal isolates). We confirmed an integro-mediated antibiotic resistance in 13 E. coli strains from municipal and animal wastewater samples, of which the Tn3 gene and virulence genes cvaC, iutA, iss, ibeA, kps, and papC were detected in six isolates. One of the strains of pathogenic E. coli from the animal wastewater contained genes ibeA with papC, iss, kpsII, Int1, Tn3, and Cit. In addition, one blaIMP gene was found in the municipal wastewater sample. This emphasises the importance of using the appropriate treatment methods to reduce the counts of antibiotic-resistant microorganisms in wastewater effluent.
Highlights
A wastewater treatment plant (WWTP) presents an important point in the protection and environmental hygiene of the urban and rural environment
A modified microdilution method with the VetMIC panel was used to detect the antimicrobial resistance in 88 E. coli strains isolated from animal wastewater (WW) and 108 strains from municipal wastewater
The highest occurrence of resistance was detected for ampicillin (85% in municipal WW and 65% in animal WW), followed by nalidixic acid (68% vs. 46%), tetracycline (61% vs. 61%), cotrimoxazole (63% vs. 37%), and streptomycin
Summary
A wastewater treatment plant (WWTP) presents an important point in the protection and environmental hygiene of the urban and rural environment. Adequate treatment can minimise the discharge of many water contaminants, mostly organic substances, chemicals, and microorganisms [1,2,3]. Many contaminants are not completely eliminated from the wastewater by treatment processes used in WWTPs. The degradation of hormones, pesticides, antibiotics, antihistaminic, and drugs is only limited, and they are commonly present in the aquatic environment [2,3]. Antibiotic-resistant organisms from wastewater enter the environment and spread resistance among water-indigenous microbes [4]. Antimicrobial resistance poses a serious global threat to humans, animals, and the environment. Deficiencies in the treatment of wastes that may contain resistant agents of bacterial infections may result in many human deaths (estimation for 2050 is 10 million human deaths) [5]
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