Samira Abduolrahimi; Ali Akbar Safari Sinegani
Abstract
Background and purpose: Municipal and hospital waste land fills that have various contaminants, especially pharmaceuticals, provide a suitable habitat for resistant bacteria which play a special role in the transfer of resistance genes. Therefore, the abundance of microorganisms and the antibiotic resistance ...
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Background and purpose: Municipal and hospital waste land fills that have various contaminants, especially pharmaceuticals, provide a suitable habitat for resistant bacteria which play a special role in the transfer of resistance genes. Therefore, the abundance of microorganisms and the antibiotic resistance of bacteria in soil and leachate samples of municipal and hospital waste burial sites in Hamedan city were investigated.Materials and methods: The characteristics of soil and leachate as well as the abundance of their microorganisms were tested and counted. Also, the percentage of bacteria resistant to ten commonly used antibiotics ampicillin, amoxicillin, cefixime, gentamicin, streptomycin, tetracycline, doxycycline, chloramphenicol, lincomycin and metronidazole was investigated. In addition, the response of bacteria from two virgin soils and new rubbish landfill to different concentrations of three antibiotics, ampicillin, gentamicin and tetracycline, were measured.Results: The log of population of fungi, actinomycetes, pseudomonas, and enterobacters, was the highest in new rubbish landfill. They were 5.35, 5.28, 6.13, and 5.98 respectively. The percentage of bacteria resistant to all ten antibiotics was higher in samples of new rubbish landfill than in other locations and lower in virgin soil than in other locations. These results were also seen in the dose response of ampicillin, gentamicin and tetracycline antibiotics. The inhibitory concentrations of these antibiotics for new rubbish landfill bacteria were 1500, 1000 and 100 mg/l, respectively. But for virgin soil, they were much less (10, 18 and 50 mg/l respectively).Conclusion: In general, this research showed that municipal and hospital waste landfills provide a suitable habitat for antibiotic-resistant bacteria, which may increase the transfer of resistant genes among soil native bacteria. Therefore, the bacteria that reach the soil through waste can be more harmful.
Samira Abduolrahimi; Ali Akbar Safari Sinegani
Abstract
Background and Purpose: The biological pollution of landfill sites for urban waste is a crucial concern. This study aims to investigate the resistance of bacteria in contaminated soils at waste burial sites against heavy metals in Hamadan.Materials and methods: The physical and chemical characteristics ...
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Background and Purpose: The biological pollution of landfill sites for urban waste is a crucial concern. This study aims to investigate the resistance of bacteria in contaminated soils at waste burial sites against heavy metals in Hamadan.Materials and methods: The physical and chemical characteristics of soils were examined, and the total amounts of metals such as copper, lead, zinc, and cadmium were measured. Additionally, pollution load index (PLI), average pollution index (PIavg), and pollution degree (Cdeg) were estimated and analyzed. Furthermore, the percentage of stable bacteria resistant to copper, lead, cadmium, and zinc in the NA culture medium was studied by measuring the logarithm of microorganism abundanceResults: Among the mentioned sites, the soil surrounding the leachate lagoon exhibited the highest levels of organic carbon, available phosphorus, and potassium. The PLI and PIavg indices for virgin soil were below one, indicating that this soil was not polluted. However, these indices were above one for the other five sites, indicating pollution. The intensity of soil pollution in these sites exceeded the permissible limit. The logarithm of population for fungi, actinomycetes, pseudomonas, and enterobacters was highest in the new rubbish landfill, with values of 5.35, 5.28, 6.13, and 5.98, respectively. The percentage of bacteria resistant to lead was 100% in all sampled soils, but in the leachate, it was lower than 64%.Conclusion: Overall, the percentages of bacteria resistant to copper, zinc, and cadmium in the new rubbish landfill site were higher compared to other sites, which may be attributed to the landfilling of urban waste in the soil.