Abstract
The scope of the study was to apply Phenotype Biolog MicroArray (PM) technology to test the antibiotic sensitivity of the bacterial strains isolated from on-site wastewater treatment facilities. In the first step of the study, the percentage values of resistant bacteria from total heterotrophic bacteria growing on solid media supplemented with various antibiotics were determined. In the untreated wastewater, the average shares of kanamycin-, streptomycin-, and tetracycline-resistant bacteria were 53, 56, and 42%, respectively. Meanwhile, the shares of kanamycin-, streptomycin-, and tetracycline-resistant bacteria in the treated wastewater were 39, 33, and 29%, respectively. To evaluate the antibiotic susceptibility of the bacteria present in the wastewater, using the phenotype microarrays (PMs), the most common isolates from the treated wastewater were chosen: Serratia marcescens ss marcescens, Pseudomonas fluorescens, Stenotrophomonas maltophilia, Stenotrophomonas rhizophila, Microbacterium flavescens, Alcaligenes faecalis ss faecalis, Flavobacterium hydatis, Variovorax paradoxus, Acinetobacter johnsonii, and Aeromonas bestiarum. The strains were classified as multi-antibiotic-resistant bacteria. Most of them were resistant to more than 30 antibiotics from various chemical classes. Phenotype microarrays could be successfully used as an additional tool for evaluation of the multi-antibiotic resistance of environmental bacteria and in preliminary determination of the range of inhibition concentration.
Highlights
Antibiotic resistance was identified by the World Health Organization as a major problem in terms of the environment and human and animal health (WHO 2014)
In order to compare the results from this study with those carried out by other researchers, the percentages of antibiotic-resistant bacteria from the total heterotrophic bacteria growing on solid media supplemented with antibiotics were calculated
The highest percentage values of antibioticresistant bacteria were in the biofilm carrier samples in facility B, e.g., rock wool which was used as a trickling biofilter media in facility B and in the sample from black plastic pieces obtained from facility C, e.g., small, fluidized units of carrier media providing a high active surface for growing of microorganisms
Summary
Antibiotic resistance was identified by the World Health Organization as a major problem in terms of the environment and human and animal health (WHO 2014). Antibiotics get into soil and water, mainly through wastewater treatment plant effluents, leakage from waste storage containers, agricultural waste, and application of biosolids to fields (Dias et al 2015). The conventional methods for susceptibility testing require the isolation of the bacteria from the environmental samples and culturing on the appropriate media that contain antibiotic(s) (Dias et al 2015). The most popular are growth inhibition assays performed in broth or by an agar disc diffusion method. In a dilution-based growth inhibition assay, the minimum inhibitory concentration (MIC) of an antibiotic can be calculated for each bacterial isolate, and the bacteria are classified as being susceptible or resistant to the antibiotic
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