Abstract
The study monitored the effect of tetracycline on bacterial biofilm formation and compared biofilm formation by resistant bacterial strains in different phases of the wastewater treatment process in wastewater treatment plant (WWTP). The crystal violet staining method was used to evaluate the biofilm formation. Biofilm-related bacterial properties were characterized by hydrophobicity, autoaggregation and motility tests. The relative abundance of tetracycline resistance genes (tetW, tetM, tetO, tetA and tetB) in wastewaters were subsequently quantified using qPCR. The results show that the isolates from the nitrification tank produce biofilm with up to 10 times greater intensity relative to the isolates from the sedimentation tank. In isolates of Aeromonas sp. from the nitrification tank, increased biofilm production in the occurrence of tetracycline from a concentration of 0.03125 µg/mL was observed. The tetW gene showed the highest relative abundance out of all the tested genes. From the sampling points, its abundance was the highest in the sedimentation tank of the WWTP. Based on these results, it can be assumed that resistant bacteria are able to form a biofilm and sub-inhibitory tetracycline concentrations induce biofilm formation. WWTPs thus represent a reservoir of antibiotic resistance genes and contribute to the spread of resistance in the natural environment.
Highlights
Wastewater treatment plants (WWTPs) are known to be important sources of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs)
The concentration of the antibiotic tetracycline was determined with UHPLC-MS/MS in wastewater samples from nitrification and sedimentation tanks of the wastewater treatment plant (WWTP)
The study monitored the effect of the antibiotic tetracycline on biofilm formation by resistant bacterial strains isolated from different phases of the wastewater treatment process
Summary
Wastewater treatment plants (WWTPs) are known to be important sources of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs). ARGs and ARB are continuously released into the environment and can transfer antibiotic resistance to susceptible microorganisms [1]. WWTP treatment processes are ideal environments for the development and spread of antibiotic resistance because a large number of bacteria are constantly exposed to antibiotics in low concentrations [2]. There are many microorganisms present in the wastewater, such as bacteria, viruses, protozoa or fungi [3]. A study on the spread of antibiotic resistance has shown strains that become multi-resistant, such as Acinetobacter spp., Aeromonas spp. and Pseudomonas spp. These are embodied in the microbial communities in municipal WWTPs and Processes 2020, 8, 989; doi:10.3390/pr8080989 www.mdpi.com/journal/processes
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