Drug resistance in airborne bacteria isolated from waste management and wastewater treatment plants in Olsztyn

Wastewater treatment plants (WWTPs) and municipal waste management plants (MWMPs) emit bioaerosols containing potentially pathogenic biological components which post a threat for human health. Microbiological monitoring supports evaluations of the antibiotic resistance (AR) of airborne microorganisms and the relevant health risks. The aim of this study was to analyze the microbiological quality of air sampled in a WWTP and MWMP in Olsztyn based on total bacterial counts, the presence of bacteria resistant to three antibiotic classes (beta-lactams, tetracyclines and chloramphenicol) and genes encoding resistance to these antibiotics (blaTEM, blaSHV, blaCMY-2, blaAmpC, tet(M), tet(A), tet(X), tet(B), cmlA, floR, fexA, fexB and catA1 ). Bacterial counts were higher in air samples collected from the MWMP (~104 CFU/m3) than from the WWTP (101–103 CFU/m3). A similar trend was noted in the counts of antibiotic resistant bacteria (ARB). The abundance of ARB did not exceed 1.7 x 102 CFU/m3 in WWTP samples, but was higher at up to 4.2 x 103 CFU/m3 in MWMP samples. Bacteria resistant to doxycycline were least prevalent in the analyzed ARB. In the group of 49 tested bacterial strains, 44 harbored at least one of the analyzed antibiotic resistance genes (ARGs). A comparison of ARGs in all bacterial strains isolated from WWTP and MWMP air samples revealed the highest diversity and prevalence of ARGs in the samples collected in the mechanical segment of the waste processing line in MWMP and the biological segment of the wastewater processing line in WWTP. The results of this study point to high microbiological contamination of air in MWMPs and WWTPs which are reservoirs of ARB and ARGs and potential sources of AR

Anaerobic Digestion in the Presence of Antimicrobials—Characteristics of Its Parameters and the Structure of Methanogens

Antibiotics are widely used in human and veterinary medicine, and they are accumulated in various types of waste, including sewage sludge (SS) and cattle slurry (CS), processed by anaerobic digestion (AD). Anaerobic treatment is a method enabling the stabilization of these substrates before transferring to the environment. The presence of contaminants, such as antimicrobials, in organic substrates processed by AD is not regulated by law. The accumulation of antimicrobials in SS and CS is a crucial issue because it may reduce the effectiveness of their stabilization. This study aimed to evaluate the long-term impact of growing concentrations of a mixture of antibiotics on the AD of SS and CS. Methane (CH4) yield, which is the main indicator of the efficiency of AD, was determined. Antibiotic exposure significantly decreased CH4 production only in SS (by 5–8% relative to control; p < 0.05). The copy numbers of the mcrA gene, a functional marker of methanogenesis, were not reliable indicators of CH4 yields in either substrate. During long-term AD, the average concentrations of the mcrA gene were determined at 108 in 1 g of SS digestate and from 108 to 109 in 1 g of CS digestate samples. At the end of long-term AD, methanogens belonging to the family Methanosarcinaceae were more prevalent than methanogens of the family Methanosaetaceae both in SS and CS samples (107 and 108–109 gene copies in 1 g of digestate, respectively)

Impact of Anthropogenic Activities on the Dissemination of ARGs in the Environment—A Review

Over the past few decades, due to the excessive consumption of drugs in human and veterinary medicine, the antimicrobial resistance (AR) of microorganisms has risen considerably across the world, and this trend is predicted to intensify. Many worrying research results indicate the occurrence of pools of AR, both directly related to human activity and environmental factors. The increase of AR in the natural environment is mainly associated with the anthropogenic activity. The dissemination of AR is significantly stimulated by the operation of municipal facilities, such as wastewater treatment plants (WWTPs) or landfills, as well as biogas plants, agriculture and farming practices, including animal production and land application of manure. These activities entail a risk to public health by spreading bacteria resistant to antimicrobial products (ARB) and antibiotic resistance genes (ARGs). Furthermore, subinhibitory concentrations of antimicrobial substances additionally predispose microbial consortia and resistomes to changes in particular environments that are permeated by these micropollutants. The current state of knowledge on the fate of ARGs, their dissemination and the complexity of the AR phenomenon in relation to anthropogenic activity is inadequate. This review summarizes the state-of-the-art knowledge on AR in the environment, in particular focusing on AR spread in an anthropogenically altered environment and related environmental consequences

Impact of type of wastewater treatment process on the antibiotic resistance of bacterial populations

Antibiotic resistant bacteria reach the environment directly with faeces, and indirectly with sewage discharged from wastewater treatment plants (WWTPs). The aim of the study was to determine the level of removal of bacteria during wastewater treatment. Samples of untreated and treated sewage were collected from 13 WWTPs with different capacity, modification of treatment and type of inflowing wastewater. Microbiological characterization of the samples included determination of the total number of bacteria resistant (ARB) to β-lactams and tetracyclines as well as the number of Escherichia coli resistant to the same drugs. The counts of ARB and E. coli were determined on TSA and mFc media with/without antibiotic supplementation, respectively. The highest percent of reduction in number of ARB (at least 99.9%) and E. coli (above 99.3%) was obtained for WWTPs with A2O system. The lowest percentage reduction of ARB and E. coli was observed for WWTPs operating with SBR system. The lowest number of microorganisms resistant to analyzed antibiotics was observed for ARB and E. coli resistant to cefotaxime and doxycycline. The results indicate a large variation in the removal of antibiotic-resistant bacteria in WWTPs depending on modifications of treatment system and type of inflowing wastewater

Quantitative Occurrence of Antibiotic Resistance Genes among Bacterial Populations from Wastewater Treatment Plants Using Activated Sludge

Wastewater treatment plants (WWTPs) are an important reservoir in the development of drug resistance phenomenon and they provide a potential route of antibiotic resistance gene (ARGs) dissemination in the environment. The aim of this study was to assess the role of WWTPs in the spread of ARGs. Untreated and treated wastewater samples that were collected from thirteen Polish WWTPs (applying four different modifications of activated sludge⁻based treatment technology) were analyzed. The quantitative occurrence of genes responsible for the resistance to beta-lactams and tetracyclines was determined using the real-time PCR method. Such genes in the DNA of both the total bacterial population and of the E. coli population were analyzed. Among the tested genes that are responsible for the resistance to beta-lactams and tetracyclines, blaOXA and blaTEM and tetA were dominant, respectively. This study found an insufficient reduction in the quantity of the genes that are responsible for antibiotic resistance in wastewater treatment processes. The results emphasize the need to monitor the presence of genes determining antibiotic resistance in the wastewater that is discharged from treatment plants, as they can help to identify the hazard that treated wastewater poses to public health

Seasonal and Technological Shifts of the WHO Priority Multi-Resistant Pathogens in Municipal Wastewater Treatment Plant and Its Receiving Surface Water: A Case Study

The present study was focused on the identification of multi-resistant bacteria from the WHO priority pathogens list in the samples taken from different stages of the full-scale municipal wastewater treatment plant and receiving water. Additionally, the seasonal variations of the selected multi-resistant pathogens were analyzed in the samples. In order to the aim of the study, the metagenomic DNA from the collected samples was isolated and sequenced. The samples were collected in three campaigns (spring, summer, autumn). Metagenomic DNA was isolated by the commercial kits, according to the manufacturer’s instruction. Illumina sequencing system was employed, and the R program was used to metagenomic analysis. It was found that the wastewater samples and receiving water contained the multi-resistant bacteria from the WHO priority pathogens list. The seasonal and technological variations affected the distribution of the pathogens in the wastewater. No effect of the effluent on the pathogens in the receiving water was observed. The results indicated that antibiotic-resistant “priority pathogens” from the WHO list are there in the waste- and receiving water. Technological process and seasons effected their distribution in the environment. Metagenomic analysis can be used as sufficient tool in microbiological and human health risk assessment

The prevalence of virulence genes specific for Escherichia coli in wastewater samples from wastewater treatment plants with the activated sludge process

Treated wastewater evacuated into the aquatic environment is a potential reservoir of pathogenic and virulent bacteria. The aim of this study was to analyze the presence of genes encoding virulence in E. coli bacteria in samples of untreated (UWW) and treated (TWW) wastewater from 13 wastewater treatment plants deploying various sewage treatment methods. Wastewater samples were passed through polycarbonate membrane filters, and genomic DNA was extracted. Virulence genes specific for E. coli were detected by standard PCR and were grouped according to their association with different pathotypes. The stx2 gene was most prevalent in samples of UWW, and the eae gene was most frequently detected in samples of TWW. An analysis of virulence markers revealed a predominance of genes characteristic of STEC and EIEC pathotypes. The highest variability of virulence genes was observed in wastewater treatment plants where sewage is treated mechanically and biologically, and the lowest variability was noted in plants deploying the A2/O treatment process (3-stage Bardenpho). In several plants, the prevalence of virulence genes increased after treatment. The results of this study suggest that wastewater treatment plants are significant reservoirs of virulent bacteria. The evacuation of TWW into water bodies can contribute to the dissemination of virulence genes in the environment, which poses a serious health hazard for humans and animals