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The presence of antimicrobial resistance genes (ARGs) in the microbiome of freshwater communities is a consequence of thousands of years of evolution but also of the pressure exerted by anthropogenic activities, with potential negative impact on environmental and human health. In this study, we investigated the distribution of ARGs in Lake Tanganyika (LT)'s water column to define the resistome of this ancient lake. Additionally, we compared the resistome of LT with that of Lake Baikal (LB), the oldest known lake with different environmental characteristics and a lower anthropogenic pollution than LT. We found that richness and abundance of several antimicrobial resistance classes were higher in the deep water layers in both lakes. LT Kigoma region, known for its higher anthropogenic pollution, showed a greater richness and number of ARG positive MAGs compared to Mahale. Our results provide a comprehensive understanding of the antimicrobial resistome of LT and underscore its importance as reservoir of antimicrobial resistance. In particular, the deepest water layers of LT are the main repository of diverse ARGs, mirroring what was observed in LB and in other aquatic ecosystems. These findings suggest that the deep waters might play a crucial role in the preservation of ARGs in aquatic ecosystems.
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Antiinfecciosos , Microbiota , Humanos , Lagos , Agua , Tanzanía , Genes Bacterianos , AntibacterianosRESUMEN
Microplastic particles are persistent micropollutants that provide a substrate for the growth of bacterial biofilms, posing a threat to the environment. This study explores the changes in commercially available food containers made of conventional (polypropylene PP, polyethylene terephthalate PET), innovative biodegradable (Mater-Bi) and natural (wood and cellulose) materials, when introduced in the surface waters of Lake Maggiore for 43 days. Spectral changes revealed by FT-IR spectroscopy in PET and Mater-Bi, and changes in thermal properties of all human-made material tested indicated a degradation process occurred during environmental exposure. Despite similar bacterial richness, biofilms on PET, PP, and Mater-Bi differed from natural material biofilms and the planktonic community. Human-made material communities showed a higher proportion of potential pathogens, with PET and PP also exhibiting increased abundances of antibiotic resistance genes. Overall, these findings stress the need for dedicated strategies to curb the spread of human-made polymers in freshwaters, including innovative materials that, due to their biodegradable properties, might be perceived less hazardous for the environment.
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Plásticos Biodegradables , Humanos , Plásticos , Plancton , Espectroscopía Infrarroja por Transformada de Fourier , Polipropilenos , Microplásticos , BacteriasRESUMEN
Wastewater treatment plants are hotspots for the release of antimicrobial resistant pathogenic bacteria into aquatic ecosystems, significantly contributing to the cycle of antimicrobial resistance. Special attention should be paid to antimicrobial resistant ESKAPE bacteria, which have been identified as high-priority targets for control measures. Among them, Klebsiella pneumoniae is particularly noteworthy. In this study, we collected wastewater samples from the inlet, sedimentation tank, and effluent water of a wastewater treatment plant in June, July, October, and November of 2018. We detected and characterized 42 K. pneumoniae strains using whole genome sequencing (15 from the inlet, 8 from the sedimentation tank, and 19 from the effluent). Additionally, the strains were tested for their antimicrobial resistance phenotype. Using whole genome sequencing no distinct patterns were observed in terms of their genetic profiles. All strains were resistant to tetracycline, meanwhile 60%, 47%, and 37.5% of strains isolated from the inlet, sedimentation tank, and effluent, respectively, were multidrug resistant. Some of the multidrug resistant isolates were also resistant to colistin, and nearly all tested positive for the eptB and arnT genes, which are associated with polymyxin resistance. Various antimicrobial resistance genes were linked to mobile genetic elements, and they did not correlate with detected virulence groups or defense systems. Overall, our results, although not quantitative, highlight that multidrug resistant K. pneumoniae strains, including those resistant to colistin and genetically unrelated, being discharged into aquatic ecosystems from wastewater treatment plants. This suggests the necessity of monitoring aimed at genetically characterizing these pathogenic bacteria.
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Introduction: Constructed wetlands (CWs) are nature-based solutions for wastewater treatment where the root system microbiome plays a key role in terms of nutrient and pollutant removal. Nonetheless, little is known on plant-microbe interactions and bacterial population selection in CWs, which are mostly characterized in terms of engineering aspects. Methods: Here, cultivation-independent and cultivation-based analyses were applied to study the bacterial communities associated to the root systems of Phragmites australis and Typha domingensis co-occurring in the same cell of a CW receiving primary treated wastewaters. Results and discussion: Two endophytic bacteria collections (n = 156) were established aiming to find novel strains for microbial-assisted phytodepuration, however basing on their taxonomy the possible use of these strains was limited by their low degrading potential and/or for risks related to the One-Health concept. A sharp differentiation arose between the P. australis and T. domingensis collections, mainly represented by lactic acid bacteria (98%) and Enterobacteriaceae (69%), respectively. Hence, 16S rRNA amplicon sequencing was used to disentangle the microbiome composition in the root system fractions collected at increasing distance from the root surface. Both the fraction type and the plant species were recognized as drivers of the bacterial community structure. Moreover, differential abundance analysis revealed that, in all fractions, several bacteria families were significantly and differentially enriched in P. australis or in T. domingensis. CWs have been also reported as interesting options for the removal of emerging contaminants (e.g, antibiotic resistance genes, ARGs). In this study, ARGs were mostly present in the rhizosphere of both plant species, compared to the other analyzed fractions. Notably, qPCR data showed that ARGs (i.e., ermB, bla TEM, tetA) and intl1 gene (integrase gene of the class 1 integrons) were significantly higher in Phragmites than Typha rhizospheres, suggesting that macrophyte species growing in CWs can display a different ability to remove ARGs from wastewater. Overall, the results suggest the importance to consider the plant-microbiome interactions, besides engineering aspects, to select the most suitable species when designing phytodepuration systems.
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Antibiotic resistance genes (ARGs) are abundant in aquatic ecosystems affected by human activities. Understanding the fate of ARGs across different ecosystems is essential because of the significant role aquatic environments play in the cycle of antibiotic resistance. We quantified selected ARGs in Lake Maggiore, its main tributaries, and the effluent of the main wastewater treatment plant (WWTP) discharging directly into the lake. We linked their dynamics to the different anthropogenic impacts in each tributary's watershed. The dynamics of tetA in the lake were influenced by those of the rivers and the WWTP effluent, and by the concentration of N-NH4, related to anthropogenic pollution, while sul2 abundance in the lake was not influenced by any water inflow. The dynamics of the different ARGs varied across the different rivers. Rivers with watersheds characterized by high population density, touristic activities, and secondary industries released more ARGs, while ermB correlated with higher numbers of primary industries. This study suggests a limited contribution of treated wastewater in the spread of ARGs, indicating as prevalent origin other sources of pollution, calling for a reconsideration on what are considered the major sources of ARGs into the environment.
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Antibacterianos , Genes Bacterianos , Humanos , Antibacterianos/farmacología , Antibacterianos/análisis , Lagos , Ecosistema , Farmacorresistencia Microbiana/genética , RíosRESUMEN
Petroleum-based microplastic particles (MPs) are carriers of antimicrobial resistance genes (ARGs) in aquatic environments, influencing the selection and spread of antimicrobial resistance. This research characterized MP and natural organic particle (NOP) bacterial communities and resistomes in the Tyrrhenian Sea, a region impacted by plastic pollution and climate change. MP and NOP bacterial communities were similar but different from the free-living planktonic communities. Likewise, MP and NOP ARG abundances were similar but different (higher) from the planktonic communities. MP and NOP metagenome-assembled genomes contained ARGs associated with mobile genetic elements and exhibited co-occurrence with metal resistance genes. Overall, these findings show that MPs and NOPs harbor potential pathogenic and antimicrobial resistant bacteria, which can aid in the spread of antimicrobial resistance. Further, petroleum-based MPs do not represent novel ecological niches for allochthonous bacteria; rather, they synergize with NOPs, collectively facilitating the spread of antimicrobial resistance in marine ecosystems.
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Bacterias , Microplásticos , Bacterias/genética , Bacterias/efectos de los fármacos , Microplásticos/toxicidad , Contaminantes Químicos del Agua/análisis , Microbiota/efectos de los fármacos , Farmacorresistencia Bacteriana/genética , Monitoreo del Ambiente , Agua de Mar/microbiología , Agua de Mar/químicaRESUMEN
Aquatic ecosystems are crucial in the antimicrobial resistance cycle. While intracellular DNA has been extensively studied to understand human activity's impact on antimicrobial resistance gene (ARG) dissemination, extracellular DNA is frequently overlooked. This study examines the effect of anthropogenic water pollution on microbial community diversity, the resistome, and ARG dissemination. We analyzed intracellular and extracellular DNA from wastewater treatment plant effluents and lake surface water by shotgun sequencing. We also conducted experiments to evaluate anthropogenic pollution's effect on transforming extracellular DNA (using Gfp-plasmids carrying ARGs) within a natural microbial community. Chemical analysis showed treated wastewater had higher anthropogenic pollution-related parameters than lake water. The richness of microbial community, antimicrobial resistome, and high-risk ARGs was greater in treated wastewaters than in lake waters both for intracellular and extracellular DNA. Except for the high-risk ARGs, richness was significantly higher in intracellular than in extracellular DNA. Several ARGs were associated with mobile genetic elements and located on plasmids. Furthermore, Gfp-plasmid transformation within a natural microbial community was enhanced by anthropogenic pollution levels. Our findings underscore anthropogenic pollution's pivotal role in shaping microbial communities and their antimicrobial resistome. Additionally, it may facilitate ARG dissemination through extracellular DNA plasmid uptake.
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Aguas Residuales , Aguas Residuales/microbiología , Farmacorresistencia Microbiana/genética , Lagos/microbiología , Genes Bacterianos/efectos de los fármacos , Contaminación del Agua , Microbiología del Agua , Microbiota/efectos de los fármacos , Antibacterianos/farmacología , Plásmidos/genética , Farmacorresistencia Bacteriana/genética , Bacterias/efectos de los fármacos , Bacterias/genética , Bacterias/clasificaciónRESUMEN
The impact of Fenton oxidation (FO) and Air stripping (AS) pre-treatments on the bacterial community of a biological activated sludge (B-AS) process for the co-treatment of mature landfill leachate (MLL) and urban wastewater (UWW) was assessed. In this work high-throughput sequencing was used to identify changes in the composition of the bacterial communities when exposed to different landfill leachate's pre-treatments. The combination of FO and AS to increase biodegradability (BOD5/COD) and reduce ammonia concentration (NH3) respectively, allowed to successfully operate the B-AS and effectively treat MLL. In particular, BOD5/COD resulted to be the key factor for bacterial community shifting. The microbiological community of the B-AS, mainly composed by the phylum Bacteroidota (Saprospiraceae, PHOS-HE51, Chitinophagaceae) after FO pre-treatment, shifted to Pseudomonadota (Caulobacteraceae and Hyphomicrobiaceae) when FO was not used. At the same time a drastic reduction in BOD5 removal was observed (90%-58%). On the other hand, high NH3 concentration affected the abundance of the family Saprospiraceae, known to play a key role in the degradation of complex organic compounds in B-AS. The results obtained suggest that a suitable combination of pre-treatments can reduce the negative effect of MLL on the B-AS process, reducing the pressure on autochthonous bacteria and therefore the acclimatization time of the biological process.
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Aguas Residuales , Contaminantes Químicos del Agua , Aguas del Alcantarillado , Contaminantes Químicos del Agua/análisis , Peróxido de Hidrógeno/química , Hierro/química , Oxidación-Reducción , Aclimatación , Bacterias/genéticaRESUMEN
Wastewater treatment plants are among the main hotspots for the release of antibiotic resistance genes (ARGs) into the environment. ARGs in treated wastewater can be found in the intracellular DNA (iDNA) and in the extracellular DNA (eDNA). In this study, we investigated the fate and the distribution (either in eDNA or in iDNA) of ARGs in the treated wastewaters pre and post-disinfection by shotgun metagenomics. The richness of the intracellular resistome was found to be higher than the extracellular one. However, the latter included different high risk ARGs. About 11% of the recovered metagenome assembled genomes (MAGs) from the extracted DNA was positive for at least one ARG and, among them, several were positive for more ARGs. The high-risk ARG bacA was the most frequently detected gene among the MAGs. The disinfection demonstrated to be an important driver of the composition of the antibiotic resistomes. Our results demonstrated that eDNA represents an important fraction of the overall ARGs, including a number of high-risk ARGs, which reach the environment with treated wastewater effluents. The studied disinfections only marginally affect the whole antibiotic resistome but cause important shifts from intracellular to extracellular DNA, potentially threating human health.
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Antibacterianos , Aguas Residuales , Humanos , Antibacterianos/farmacología , Genes Bacterianos , ADN , Farmacorresistencia Microbiana/genéticaRESUMEN
Bacteriophages are known as players in the transmission of antimicrobial resistance genes (ARGs) by horizontal gene transfer. In this study, we characterized the bacteriophage community and the associated ARGs to estimate the potential for phages to spread ARGs in aquatic ecosystems analyzing the intra- and extracellular DNA isolated from two wastewater treatment plants (WWTPs) by shotgun metagenomics. We compared the phage antimicrobial resistome with the bacterial resistome and investigated the effect of the final disinfection treatment on the phage community and its resistome. Phage community was mainly composed by Siphoviridae and other members of the order Caudovirales. The final disinfection only marginally affected the composition of the phage community, and it was not possible to measure its effect on the antimicrobial resistome. Indeed, only three phage metagenome-assembled genomes (pMAGs) annotated as Siphoviridae, Padoviridae, and Myoviridae were positive for putative ARGs. Among the detected ARGs, i.e., dfrB6, rpoB mutants, and EF-Tu mutants, the first one was not annotated in the bacterial MAGs. Overall, these results demonstrate that bacteriophages limitedly contribute to the whole antimicrobial resistome. However, in order to obtain a comprehensive understanding of the antimicrobial resistome within a microbial community, the role of bacteriophages needs to be investigated. IMPORTANCE WWTPs are considered hotspots for the spread of ARGs by horizontal gene transfer. In this study, we evaluated the phage composition and the associated antimicrobial resistome by shotgun metagenomics of samples collected before and after the final disinfection treatment. Only a few bacteriophages carried ARGs. However, since one of the detected genes was not found in the bacterial metagenome-assembled genomes, it is necessary to investigate the phage community in order to gain a comprehensive overview of the antimicrobial resistome. This investigation could help assess the potential threats to human health.
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This study investigates the antibiotic resistance fate in the urban water cycle, evaluating the dynamics of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in three different full-scale wastewater treatment plants (WWTPs) and two drinking water treatment plants (DWTPs) located in the same geographical area (North-West of Italy). ARB (tetracycline-, ampicillin-, and sulfonamide-resistant bacteria) were quantified by plate counting and the abundances of selected ARGs (i.e., tetA, blaTEM, and sulII) and intI1 gene were measured using quantitative real-time PCR (qPCR). Higher concentrations of ARB and ARGs were observed in the WWTPs with respect to the DWTPs identifying the WWTP as hotspot for the spread of antibiotic resistances. Although a significant reduction of ARB and ARGs was observed in WWTPs and DWTPs after the treatment, none of the detected ARB or ARGs was completely removed in drinking water. The stability of the antibiotic-resistant rates between inlet and outlet associated with the reduction of relative ARG abundances underlined that both the treatments (WWTs and DWTs) did not apply any selective pressure. The overall results highlighted the importance to investigate the antibiotic resistance dynamics in aquatic ecosystems involved in urban water cycle integrating the information obtained by culture-dependent method with the culture-independent one and the need to monitor the presence of ARB and ARGs mainly in drinking water that represents a potential route of transmission to human.
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Agua Potable , Purificación del Agua , Humanos , Aguas Residuales , Eliminación de Residuos Líquidos/métodos , Genes Bacterianos , Bacterias/genética , Ecosistema , Agua Potable/análisis , Antagonistas de Receptores de Angiotensina/análisis , Ciclo Hidrológico , Inhibidores de la Enzima Convertidora de Angiotensina , Antibacterianos/farmacología , Antibacterianos/análisisRESUMEN
The risk for human health posed by polluted aquatic environments, and especially those carrying antibiotic resistance genes (ARGs) of clinical interest, is still debated. This is because of our limited knowledge of the dynamics of antimicrobial resistance in the environment, the selection mechanisms underlying the spread of ARGs, and the ecological factors potentially favoring their return to humans. The Class 1 integron is one of the most effective platforms for the dissemination of ARGs. In this study we investigated a freshwater system consisting of a lake-river-lake continuum, determining the abundance of class 1 integrons and their associated ARGs by a modulated metagenomic approach. Bacterial abundance and community composition were used to identify the potential carriers of class 1 integrons and their associated ARGs over a period of six months. Class 1 integrons and their ARG cargoes were significantly more abundant in riverine sampling sites receiving treated wastewater. Further, class 1 integrons carried ARGs ranked at the highest risk for human health (e.g., catB genes), in particular, genes encoding resistance to aminoglycosides. Genera of potential pathogens, such as Pseudomonas and Escherichia-Shigella, were correlated with class 1 integrons. The lake-river-lake system demonstrated a clear relationship between the integrase gene of class 1 integrons (intI1) and anthropogenic impact, but also a strong environmental filtering that favored the elimination of intI1 once the human derived stressors were reduced. Overall, the results of this study underline the role class 1 integrons as proxy of anthropogenic pollution and suggest this genetic platform as an important driver of aminoglycoside resistance genes, including high risk ARGs, of potential concern for human health.
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Antibacterianos , Integrones , Humanos , Integrones/genética , Antibacterianos/farmacología , Efectos Antropogénicos , Farmacorresistencia Bacteriana/genética , Genes Bacterianos , LagosRESUMEN
Aquatic ecosystems in anthropogenically impacted areas are important reservoirs of antibiotic resistance genes (ARGs) of allochthonous origin. However, the dynamics of the different ARGs within the bacterial communities of lakes and rivers, as well as the factors that drive their selection, are not completely understood. In this study, we analysed the fate of the bacterial resistome (total content of ARGs and of metal resistance genes, MRGs) for a period of six months (summer-winter) in a continuum lake-river-lake system (Lake Varese, River Bardello, Lake Maggiore) in Northern Italy, by shotgun metagenomics. The metagenomic data were then compared with chemical, physical and microbiological data, to infer the role of anthropogenic pressure in the different sampling stations. ARGs and MRGs were more abundant and diverse in the River Bardello, characterised by the highest anthropogenic pollution. The date of sampling influenced ARGs and MRGs, with higher abundances in summer (August) than in fall or in winter, when the impact of the treated wastewater discharge in the river was limited by a higher water flow from Lake Varese. ARG and MRG abundances were significantly correlated and they co-occurred in the main network analysis modules with potential pathogenic bacteria. Different levels of anthropogenic impact selectively promoted specific ARGs while others, generally abundant in waters, were not affected by anthropogenic pressure. Reducing the level of anthropogenic pressure resulted in a rapid decrease of most ARGs. From our results, the role of anthropogenic pressure in promoting the spread of specific antibiotic resistances and of potential pathogens in aquatic ecosystem becomes clear. Finally we highlight the strict correlation between ARGs and MRGs suggesting their potential co-selection in stressed aquatic bacterial communities.
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Ecosistema , Genes Bacterianos , Bacterias/genética , Farmacorresistencia Microbiana/genética , Lagos/microbiología , Ríos/microbiología , Antibacterianos/farmacologíaRESUMEN
Wastewater treatment plants (WWTPs) are among the main hotspots of antibiotic resistance genes (ARGs) in the environment. Previously, we demonstrated that, by increasing anthropogenic pollution, the antibiotic resistome persisted in the microbial community of rivers and lakes, independently by changes in community composition. In this study, we reanalysed the data to test for the relation of metal resistance genes (MRGs), plasmids, and integrons to the persistence of the antibiotic resistome. The experiment consisted in replicated co-cultures of riverine or lacustrine microbial communities and WWTP effluents in different proportions. Samples before (T0) and after a short period of incubation (TF) were collected and community metagenomic data were obtained by shotgun sequencing. The data were processed to annotate MRGs, plasmids, and integrases. The integrases stabilized in the aquatic environment following the degree of contamination with effluent water (in particular in one site), whereas MRGs and plasmids showed stochastic trajectories. These results confirm the potential correlation between integrons and anthropogenic pollution, and the reliability of intI1 as a pollution marker. Only in one site MRGs, plasmids, and ARGs were correlated, highlighting their partial contribution to the persistence of ARGs in surface waters.
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Antibacterianos , Genes Bacterianos , Integrasas/genética , Reproducibilidad de los Resultados , Aguas ResidualesRESUMEN
Seas and oceans are a global reservoir of antibiotic resistance genes (ARGs). Only a few studies investigated the dynamics of ARGs along the water column of the Black Sea, a unique environment, with a peculiar geology, biology and history of anthropogenic pollution. In this study, we analyzed metagenomic data from two sampling campaigns (2013 and 2019) collected across three different sites in the Western Black Sea at depths ranging from 5 to 2000 m. The data were processed to annotate ARGs, metal resistance genes (MRGs) and integron integrase genes. The ARG abundance was significantly higher in the deep water layers and depth was the main driver of beta-diversity both for ARGs and MRGs. Moreover, ARG and MRG abundances strongly correlated (r = 0.95). The integron integrase gene abundances and composition were not influenced by the water depth and did not correlate with ARGs. The analysis of the obtained MAGs showed that some of them harbored intI gene together with several ARGs and MRGs, suggesting the presence of multidrug resistant bacteria and that MRGs and integrons could be involved in the selection of ARGs. These results demonstrate that the Black Sea is not only an important reservoir of ARGs, but also that they accumulate in the deep water layers where co-selection with MRGs could be assumed as a relevant mechanism of their persistence.
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Antibacterianos , Genes Bacterianos , Antibacterianos/farmacología , Mar Negro , Farmacorresistencia Microbiana/genética , Integrasas/genética , Metagenómica/métodos , Metales , AguaRESUMEN
A side effect of antibiotic usage is the emergence and dissemination of antibiotic resistance genes (ARGs) within microbial communities. The spread of ARGs among pathogens has emerged as a public health concern. While the distribution of ARGs is documented on a global level, their routes of transmission have not been clarified yet; for example, it is not clear whether and to what extent the emergence of ARGs originates in farms, following the selective pressure exerted by antibiotic usage in animal husbandry, and if they can spread into the environment. Here we address this cutting edge issue by combining data regarding antimicrobial usage and quantitative data from selected ARGs (blaTEM, blaCTXM, ermB, vanA, qnrS, tetA, sul2, and mcr-1) encoding for resistance to penicillins, macrolides-lincosamides-streptogramins, glycopeptides, quinolones, tetracyclines, sulfonamides, and colistin at the farm level. Results suggest that dairy farms could be considered a hotspot of ARGs, comprising those classified as the highest risk for human health and that a correlation existed between the usage of penicillins and blaTEM abundances, meaning that, although the antibiotic administration is not exclusive, it remains a certain cause of the ARGs' selection and spread in farms. Furthermore, this study identified the role of calves as the main source of ARGs spread in dairy farms, claiming the need for targeted actions in this productive category to decrease the load of ARGs along the production chain.
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Antibacterianos , Genes Bacterianos , Animales , Antibacterianos/farmacología , Bovinos , Farmacorresistencia Microbiana/genética , Granjas , Penicilinas/farmacologíaRESUMEN
Wastewater treatment plants (WWTPs) efficiently retain microplastic particles (MPs) generated within urban areas. Among the wastewater treatment steps, disinfection has not been characterized for its potential MPs retention activity, although it has been reported that processes used to abate the bacterial load could also affect MPs concentration. For this reason, we evaluated the MPs concentration across the overall wastewater treatment process and before and after the disinfection step in four small/medium WWTPs located in the north of Italy. Most of the MPs found in the samples were fibers or fragments, smaller than 500 µm, mainly composed of polyethylene, polypropylene, or polyethylene terephthalate. The retention efficiency at the outlets was higher than 94% in all the plants analyzed. More interestingly, the disinfection treatments adopted by the different WWTPs reduced MPs concentration from a minimum of 9.1% (UV treatment) to a maximum of 67.6% (chlorination), promoting a further increase of the overall retention efficiency of the WWTPs from 0.4 to 0.7%. Quantitatively, the disinfection contributes to the MPs reduction in the outlets by retaining 0.5-6.7 million MPs per day, in WWTPs that discharge 2.7-12 million MPs per day. The results of the present work underline the importance of a careful choice of the steps that constitute the wastewater treatment, including disinfection, in order to minimize MPs discharge into the natural ecosystems.
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Contaminantes Químicos del Agua , Purificación del Agua , Desinfección , Ecosistema , Monitoreo del Ambiente , Microplásticos , Plásticos , Eliminación de Residuos Líquidos , Aguas Residuales , Contaminantes Químicos del Agua/análisisRESUMEN
Although abundant and chemically peculiar, tyre wear microplastic particles (TWP) and their impact on the microbial communities in water are largely understudied. We tested in laboratory based semi-continuous cultures the impact of TWP and of polyethylene terephthalate (PET) derived particles (following a gradient of relative abundance) on the pathobiome (the group of potential human pathogenic bacteria) of a freshwater microbial community exposed to contamination by the effluent of a urban wastewater treatment plant, for a period of 28 days. We could define the modulated impact of the two types of microplastic particles: while PET does not favour bacterial growth, it offers a refuge to several potential pathogens of allochthonous origin (from the treated sewage effluent), TWP act as an additional carbon source, promoting the development and the massive growth of a biofilm composed by fast-growing bacterial genera including species potentially harmful and competitive in abating biodiversity in surface waters. Our results demonstrate the different ecological role and impact on freshwater environments of TWP and PET particles, and the need to approach the study of this pollutant not as a whole, but considering the origin and the chemical composition of the different particles.
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Microbiota , Contaminantes Químicos del Agua , Ecosistema , Monitoreo del Ambiente , Humanos , Microplásticos/toxicidad , Plásticos/toxicidad , Tereftalatos Polietilenos , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
Antibiotic resistance is a serious concern for public health. Farm environments are relevant reservoirs of antibiotic resistant bacteria and antibiotic resistance genes (ARGs), thus strategies to limit the spread of ARGs from farms to the environment are needed. In this study a broiler farm, where antibiotics have never been used for any purpose, was selected to evaluate if this measure is effective in reducing the ARGs load in farm environment (FE) and in meat processing environment (MPE). Faecal samples from FE and MPE were processed for DNA extraction. Detection and quantification of the 16S rRNA gene and selected ARGs (blaTEM, qnrS, sul2, and tetA) were carried out by PCR and digital droplet PCR (ddPCR), respectively. Generally, the relative abundance of the quantified ARGs in FE was similar or higher than that measured in intensive farms. Furthermore, apart for tetA, no differences in relative abundances of the other ARGs between FE and MPE were determined. These results suggest that the choice to not use antibiotics in broiler farming is not so effective to limit the ARGs spread in MPE and that further sources of ARGs should be considered including the preceding production phase with particular reference to the breeding stage.
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Antibacterianos , Genes Bacterianos , Animales , Antibacterianos/análisis , Antibacterianos/farmacología , Pollos/genética , Farmacorresistencia Microbiana/genética , Granjas , ARN Ribosómico 16S/genéticaRESUMEN
Swine farms are considered a hotspot of antimicrobial resistance and may contribute to the spread of antibiotic-resistant and/or pathogenic bacteria into the environment as well as to farm workers. In this study, swine fecal samples have been collected over the primary production, selecting three categories, i.e., "Suckling piglets", "Weaning pigs" and "Fatteners", in six intensive swine farms, for two years. Feces were analysed for the detection and abundance of class 1 integrons (used as proxy of antibiotic resistance and of anthropogenic pollution), and of enterococci [fecal indicator bacteria (FIB) and potentially pathogenic for humans] by quantitative Real Time PCR. Furthermore, Enterococcus faecalis and Enterococcus faecium were isolated, analysed for the presence of the intI1 gene by Real Time PCR and genetically typed by Pulsed-Field Gel Electrophoresis. Both enterococci and class 1 integrons were significantly more abundant in the Suckling piglets (p = 0.0316 and 0.0242, respectively). About 8% of the isolated enterococci were positive for the intI1 gene by Real Time PCR. E. faecalis and E. faecium were found genetically heterogeneous and no specific pattern could be identified as the driver for their presence along the pig primary production. These findings suggest that the "Suckling piglets" category of production represents the key point where to mitigate the risk of transmission of enterococci and class 1 integrons with associated antibiotic resistance genes to humans and spread into the environment.