Fate Of Antibiotic Resistant Bacteria Research Articles

Distribution of antibiotic-resistant bacteria in aerobic composting of swine manure with different antibiotics

BackgroundLivestock manure is an important reservoir of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs). The bacterial community structure and diversity are usually studied using high-throughput sequencing that cannot provide direct evidence for ARB changes. Thus, little is known about the distribution of ARB, especially in the presence of different antibiotics in composting process. In this study, the fate of ARB was investigated in aerobic composting of swine manure, using chlortetracycline, sulfamethoxazole, lincomycin, and ciprofloxacin as typical antibiotics. The abundance and species of ARB were analyzed systematically to evaluate their ecological risk at different stages of composting.ResultsThe absolute abundance of total ARB decreased, while the relative abundance increased on day 2. The relative abundance of lincomycin-resistant bacteria was higher than other ARBs during the whole composting process. The absolute abundance of four ARBs was 9.42 × 106–2.51 × 102 CFU/g (lincomycin- > chlortetracycline- > sulfamethoxazole- > ciprofloxacin- > multiple antibiotic-resistant bacteria), and they were not completely inactivated at the end of composting. Antibiotics led to a partial proliferation of ARBs including Corynebacterium, Sporosarcina, Solibacillus, and Acinetobacter. Especially, Corynebacterium, a pathogenic genus, was observed in chlortetracycline and lincomycin treatments.ConclusionAmong the antibiotics studied, lincomycin showed the highest ecological risk, due to it expanded the range of lincomycin-resistant bacteria at the phyla level (Firmicutes, Actinobacteria, and Proteobacteria). The principal co-ordinates analysis indicated that the bacterial community structure was primarily associated with the composting stages rather than antibiotic types. Possible potential hosts and the related to the decrease of ARGs abundance were indicated based on the network analysis. The decrease of culturable Proteobacteria and the increase of culturable Firmicutes (Solibacillus, Bacillus) partially explained the high degradation rate of various ARGs with the progress of composting in this study. These results provided important information for the control of antibiotic resistance in composting.

Effect of earthworms in reduction and fate of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) during clinical laboratory wastewater treatment by vermifiltration

In the recent decades, the role of wastewater treatment plants has been entrenched for the dissemination of antibiotic resistant bacteria into the environment. The present study explores the dynamics of earthworms-microorganisms interactions involved in the high treatment efficacy of vermifiltration technology along with reduction of antibiotic resistant bacteria (ARB). This study is the first of its kind to investigate the performance efficacy of vermifilter (VF) for clinical laboratory wastewater treatment. The results of the study showed that earthworms and VF associated microbial community had a significant effect on Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) reduction (78–85%), coliforms and pathogen removal (>99.9%) and caused a significant shift in the prevalence pattern of ARB. Molecular profiling of resistance causing genes such as ESBL (blaSHV, blaTEM and blaCTX-M), MRSA (mec-A) and Colistin (mcr-1) confirmed the probable mechanisms behind the resistance pattern. The microbial community diversity in the influent, earthworm's coelomic fluid and gut and filter media layers associated with the VF assists in the formation of biofilm, which helps in the removal of pathogens from the wastewater. This biofilm formation further results in a paradigm shift in the resistance profile of ARB and ARG, specifically most effective against drugs, targeting cell wall and protein synthesis inhibition such as Ampicillin, Ticarcillin, Gentamicin and Chloramphenicol. These findings further validate vermifiltration technology as a sustainable and natural treatment technology for clinical laboratory wastewater, specifically for the removal of pathogens and antibiotic resistance.

Antibiotic resistance fate in the full-scale drinking water and municipal wastewater treatment processes: A review

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been widely identified as emerging pollutants in various aquatic compartments. Concerns have been raised that the antibiotic resistance determinants may occur in treated drinking water and wastewater, weakening the therapeutic efficacy of antibiotics and so posing threat to public health. Most often, laboratory trials are conducted to assess the removal efficiency of ARB and ARGs in individual treatment processes (e.g., disinfection). However, the random variations of microbial distribution and chemical compositions in real-world environments cannot be entirely simulated, presumably leading to false-positive results as a consequence. It is therefore useful to provide a summary of recent advancements regarding the antibiotic resistance attenuation during full-scale water/wastewater treatments, which has not been adequately evaluated so far. In this review, the prevalence, proliferation and transmission of ARB and ARGs in urban water cycle, coupled with corresponding detection methods are presented as a short overview. The fate of ARB and ARGs in the sequential drinking water and wastewater processing units is critically summarized, the aim of which is to provide guidance for improving the current water treatment facilities to further reduce the antibiotic resistance in finished water.

Fate and seasonal change of Escherichia coli resistant to different antibiotic classes at each stage of conventional activated sludge process.

This study investigated the impact of each treatment stage of the activated sludge process on the fate of antibiotic resistant bacteria (ARB) in wastewater treatment plants (WWTPs). Wastewater and sludge samples were collected monthly at each stage of a commercial-scale WWTP. After 20-25 strains of indicator Escherichia coli were isolated from each sample on Chromocult Coliform Agar, antibiotic resistance of the isolates to amoxicillin (AMX), ciprofloxacin (CIP), norfloxacin (NFX), kanamycin (KM), sulfamethoxazole/trimethoprim (ST) and tetracycline (TC) were tested with the Kirby-Bauer disk diffusion method. As a result, activated sludge in the aeration tank and return sludge had higher abundance of antibiotic resistant E. coli than influent wastewater and secondary treatment effluent. AMX resistant E. coli was enriched in return sludge at the secondary clarifier. Higher temperature was also likely to cause an increase of AMX resistant E. coli in sludge. The antibiotic resistance profile of E. coli in secondary treatment effluent was more dependent on activated sludge than influent wastewater. These results suggested that activated sludge in WWTP possibly serves as a reservoir of ARB, and that behavior of ARB in WWTP differs by antibiotic classes.

Designing Fluorescent Polymer Sensors for the Detection of Antibiotics in Wastewater

Antimicrobial resistance, where bacteria that possess a tolerance for certain antibiotics are able to proliferate, is a rapidly growing concern in the world. In Europe alone, there is an estimated 25,000 deaths per year due to resistant bacteria [1].The prevalence of broad spectrum antibiotics for treating infections means there is a significant concentration in our water systems. While most developed countries have reliable filtration systems and regulations, there still exists industrial regions where the filtration system is not suitable for the level of contamination present [2]. Developing a fast, low cost and reliable system for the detection of these drugs would allow for the identification of problem areas to target improved filtration and treatment of wastewater. The presented work demonstrates a molecularly imprinted polymer (MIP) that contains a fluorescent moiety capable of interacting with antibiotic drugs such as nafcillin and amoxicillin. MIPs act as a synthetic receptor for a specific target, similar to antibodies, through interactions between the functional groups in the monomer and the chosen target molecule. Size-specific cavities are formed during polymerization and after the target has been extracted from the resulting material, specific rebinding can occur. Upon rebinding, the target can increase the thermal resistance of the material or interact with fluorescent molecule covalently attached to the polymer. Three different fluorescent moieties were investigated, each with different chemical structures and fluorescent bands. Fluorescent polymer microparticles were first synthesized and showed comparable binding to the target as non-fluorescent ones, demonstrating that the introduced moieties did not impede imprinting. Batch rebinding was conducted for both antibiotic drugs and the imprinted polymers showed significant higher uptake compared to the non-imprinted analogues. Fluorescence was then introduced into thin film polymers, with thickness of ~1-2 um, anchored to glass. The imprinted films showed a significant increase in fluorescent response in the presence of nafcillin compared to the non-imprinted film. The fluorescent response of 9-vinylanthracene, fluorescein methacrylate and a synthesized molecule containing multiple anthracenes were compared for each target, with and without imprinting. The measured response was used in tandem with a novel thermal detection method to quantify the level of antibiotics in aqueous samples. These results demonstrate a possible avenue to create low-cost, robust sensors capable of selectively detecting drugs in wastewater with the use of multiple transducers.[1] Paphitou, N. I. Antimicrobial Resistance: Action to Combat the Rising Microbial Challenges. Int. J. Antimicrob. Agents 2013, 42, S25–S28.[2] Bouki, C.; Venieri, D.; Diamadopoulos, E. Detection and Fate of Antibiotic Resistant Bacteria in Wastewater Treatment Plants: A Review. Ecotoxicol. Environ. Saf. 2013, 91, 1–9. Figure 1

Demobilizing Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes by Electrochemical Technology: New Insights

Taking into account its merits in terms of high efficiency and low energy consumption, electrochemical (EC) technology especially bioelectrochemical system (BES) has been applied largely in reducing different antibiotics from wastewater. BES averts the spread of antibiotic resistance genes (ARGs) via forming less quantity of sludge compared with wastewater treatment plants. Nevertheless, transmembrane permeability and membrane potential could be influenced by the electrical stimulation, conducting to augmentations in the antibiotic-resistant bacteria (ARB) and ARGs in BES. This work discusses the utilization of EC technology especially BES for antibiotic reduction and the fate of ARB and ARGs in such systems. BES can effectively remove antibiotics. Nevertheless, low electric current promotes vertical and horizontal ARGs transfer during the treatment of antibiotics in BES. ARB and ARGs could be inhibited by a higher electric current. Questions regarding the potential role of BES in antibiotic removal and the consequent fate of ARGs and ARB in wastewater are presented. Further research is needed to elucidate the primary ARG transfer mechanism and to fully understand the advantages of BESs.

Fate of antibiotic resistance genes and antibiotic-resistant bacteria in water resource recovery facilities.

Many important diseases are showing resistance to commonly used antibiotics, and the resistance is potentially caused by widespread use of antibiotics for maintaining human health and improving food production. Antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) are associated with this increase, and their fate in water resource recovery facilities is an important, emerging area of research. This literature review summarizes current findings of worldwide research on the fate of ARB and ARGs in various types of treatment plants. Twenty-five published studies were reviewed which contained 215 observations in activated sludge, membrane bioreactors, anaerobic digestion, constructed wetlands, coagulation-filtration, and three types of disinfection. We found 70% decreased observations, 18% increased observations, and 12% unchanged observations of all observations in all treatment processes. Resistance genes to tetracycline were most often observed, but more studies are needed in other antibiotic resistance genes. The causes for increased abundance of ARGs and ARB are not well understood, and further studies are warranted. PRACTITIONER POINTS: Antibiotic resistance is increasing with concern that treatment plants may acclimate bacteria to antibiotics. A literature survey found 215 resistance observations with 70% decreased, 18% increased, 12% unchanged after treatment. The type of treatment process is important with activated sludge showing the greatest reductions.

Simulated wastewater reduced Klebsiella michiganensis strain LH-2 viability and corresponding antibiotic resistance gene abundance in bio-electrochemical reactors

A previous study revealed that the electrolytic stimulation process in bio-electrochemical reactors (BER) can accelerate growth of sulfadiazine (SDZ) antibiotic resistant bacteria (ARB) in nutrient broth medium. However, the influence of different medium nutrient richness on the fate of ARB and the relative abundance of their corresponding antibiotic resistance genes (ARGs) in this process is unknown. Specifically, it is not clear if the fate of ARB in minimal nutrition simulated wastewater is the same as in nutrient broth under electrolytic stimulation. Therefore, in this study, nutrient broth medium and the simulated wastewater were compared to identify differences in the relative abundance of Klebsiella michiganensis LH-2 ARGs in response to the electrolytic stimulation process, as well as the fate of the strain in simulated wastewater. Lower biomass, specific growth rates and viable bacterial counts were obtained in response to the application of increasing current to simulated wastewater medium. Furthermore, the percentage of ARB lethality, which was reflected by flow cytometry analysis, increased with current in the medium. A significant positive correlation of sul genes and intI gene relative abundance versus current was also observed in nutrient broth. However, a significant negative correlation was observed in simulated wastewater because of the higher metabolic burden, which may have led to decreased ARB viability. Further investigation showed that the decrease in ARGs abundance was responsible for decreased strain tolerance to SDZ in simulated wastewater. These results reveal that minimal nutrition simulated wastewater may reduce ARB and ARGs propagation in BER.

Bacterial lineages putatively associated with the dissemination of antibiotic resistance genes in a full-scale urban wastewater treatment plant

Urban wastewater treatment plants (UWTPs) are reservoirs of antibiotic resistance. Wastewater treatment changes the bacterial community and inevitably impacts the fate of antibiotic resistant bacteria and antibiotic resistance genes (ARGs). Some bacterial groups are major carriers of ARGs and hence, their elimination during wastewater treatment may contribute to increasing resistance removal efficiency. This study, conducted at a full-scale UWTP, evaluated variations in the bacterial community and ARGs loads and explored possible associations among them. With that aim, the bacterial community composition (16S rRNA gene Illumina sequencing) and ARGs abundance (real-time PCR) were characterized in samples of raw wastewater (RWW), secondary effluent (sTWW), after UV disinfection (tTWW), and after a period of 3 days storage to monitoring possible bacterial regrowth (tTWW-RE). Culturable enterobacteria were also enumerated.Secondary treatment was associated with the most dramatic bacterial community variations and coincided with reductions of ~2 log-units in the ARGs abundance. In contrast, no significant changes in the bacterial community composition and ARGs abundance were observed after UV disinfection of sTWW. Nevertheless, after UV treatment, viability losses were indicated ~2 log-units reductions of culturable enterobacteria. The analysed ARGs (qnrS, blaCTX-M, blaOXA-A, blaTEM, blaSHV, sul1, sul2, and intI1) were strongly correlated with taxa more abundant in RWW than in the other types of water, and which associated with humans and animals, such as members of the families Campylobacteraceae, Comamonadaceae, Aeromonadaceae, Moraxellaceae, and Bacteroidaceae.Further knowledge of the dynamics of the bacterial community during wastewater treatment and its relationship with ARGs variations may contribute with information useful for wastewater treatment optimization, aiming at a more effective resistance control.

Soil types influence the fate of antibiotic-resistant bacteria and antibiotic resistance genes following the land application of sludge composts

Sewage sludge was generally considered a significant reservoir of antibiotic resistance genes (ARGs) and could enter agricultural systems as fertilizer after composting. Soil types and the discrepancy of sludge composts could have influenced the fate of antibiotic-resistant bacteria (ARB) following the land application of sludge composts, which deserved to be clarified. Thus, the fate of ARB and ARGs following the land application of three types of sludge composts (A, B, and C) to three different soils (red soil, loess, and black soil) was investigated. The results showed that tetX, which was enriched the most during composting, did not affect the soil resistome, whereas tetG did. Soil types influenced the dynamics of ARB and ARGs significantly, whereas no significant difference was observed among compost types. The advantage of reducing ARGs during the composting process in compost B did not extend to land application. Land application of composts influenced the microbial community significantly at the early stage, but the microbial community returned to the control pattern gradually. Changes in the microbial community contributed more to the dynamics of ARGs in red and black soil compared with other factors, including co-selection from heavy metals, horizontal gene transfer, biomass and environmental factors, whereas horizontal gene transfer, reflected by intI1 levels, contributed the most in loess.

Effects ofdirect current on Klebsiella spp. viability and corresponding resistance gene expression in simulative bio-electrochemical reactors

The fate of antibiotic-resistant bacteria (ARB) and associated antibiotic-resistant gene (ARG) expression under electrolytic stimulation in bio-electrochemical reactors (BERs) was unknown. In this study, sulfadiazine resistant bacteria (Klebsiella spp.), which were isolated from a BER, were subjected to constant direct current (DC) stimulation in a simulated BER. With an increase of the current from 7 to 28 mA, it was found that lactic dehydrogenase (LDH) showed a 1.03-, 1.21-, 1.34-, and 1.46-fold value compared with the control at 48 h, indicating that the cell membrane permeability had increased. Since the adenosine triphosphate (ATP) concentration increased with the current, the specific growth rate of Klebsiella spp. increased (R = 0.98). The viable count of Klebsiella spp. reached a maximum at 19 mA and then decreased. The percentage of ARB lethality, which was reflected by flow cytometry analysis, increased from 18% (7 mA) to 37.8% (28 mA) at 48 h. Reactive oxygen species (ROS) produced from the electrolysis of water were greater with the increasing current (R = 0.94), which may be responsible for the high lethality rate of Klebsiella spp.. Scanning electronic microscope results showed that electrolytic stimulation changed the cell surface morphology with some cell disruption. An upregulation of sulII and int1 expression was observed. A significant correlation between int1 and the current (R = 0.97) were observed. Taken together, BERs possess potential risks in accelerating ARB multiplication and promoting ARG expression.

Survival of Antibiotic Resistant Bacteria and Horizontal Gene Transfer Control Antibiotic Resistance Gene Content in Anaerobic Digesters.

Understanding fate of antibiotic resistant bacteria (ARB) vs. their antibiotic resistance genes (ARGs) during wastewater sludge treatment is critical in order to reduce the spread of antibiotic resistance through process optimization. Here, we spiked high concentrations of tetracycline-resistant bacteria, isolated from mesophilic (Iso M1-1—a Pseudomonas sp.) and thermophilic (Iso T10—a Bacillus sp.) anaerobic digested sludge, into batch digesters and monitored their fate by plate counts and quantitative polymerase chain reaction (QPCR) of their corresponding tetracycline ARGs. In batch studies, spiked ARB plate counts returned to baseline (thermophilic) or 1-log above baseline (mesophilic) while levels of the ARG present in the spiked isolate [tet(G)] remained high in mesophilic batch reactors. To compare results under semi-continuous flow conditions with natural influent variation, tet(O), tet(W), and sul1 ARGs, along with the intI1 integrase gene, were monitored over a 9-month period in the raw feed sludge and effluent sludge of lab-scale thermophilic and mesophilic anaerobic digesters. sul1 and intI1 in mesophilic and thermophilic digesters correlated positively (Spearman rho = 0.457–0.829, P < 0.05) with the raw feed sludge. There was no correlation in tet(O) or tet(W) ratios in raw sludge and mesophilic digested sludge or thermophilic digested sludge (Spearman rho = 0.130–0.486, P = 0.075–0.612). However, in the thermophilic digester, the tet(O) and tet(W) ratios remained consistently low over the entire monitoring period. We conclude that the influent sludge microbial composition can influence the ARG content of a digester, apparently as a result of differential survival or death of ARBs or horizontal gene transfer of genes between raw sludge ARBs and the digester microbial community. Notably, mesophilic digestion was more susceptible to ARG intrusion than thermophilic digestion, which may be attributed to a higher rate of ARB survival and/or horizontal gene transfer between raw sludge bacteria and the digester microbial community.

Fate of antibiotic resistance bacteria and genes during enhanced anaerobic digestion of sewage sludge by microwave pretreatment

The fate of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) were investigated during the sludge anaerobic digestion (AD) with microwave-acid (MW-H), microwave (MW) and microwave-H2O2-alkaline (MW-H2O2) pretreatments. Results showed that combined MW pretreatment especially for the MW-H pretreatment could efficiently reduce the ARB concentration, and most ARG concentrations tended to attenuate during the pretreatment. The subsequent AD showed evident removal of the ARB, but most ARGs were enriched after AD. Only the concentration of tetX kept continuous declination during the whole sludge treatment. The total ARGs concentration showed significant correlation with 16S rRNA during the pretreatment and AD. Compared with unpretreated sludge, the AD of MW and MW-H2O2 pretreated sludge presented slightly better ARB and ARGs reduction efficiency.

Fate of Antibiotic Resistant Bacteria and Genes during Wastewater Chlorination: Implication for Antibiotic Resistance Control

This study investigated fates of nine antibiotic-resistant bacteria as well as two series of antibiotic resistance genes in wastewater treated by various doses of chlorine (0, 15, 30, 60, 150 and 300 mg Cl2 min/L). The results indicated that chlorination was effective in inactivating antibiotic-resistant bacteria. Most bacteria were inactivated completely at the lowest dose (15 mg Cl2 min/L). By comparison, sulfadiazine- and erythromycin-resistant bacteria exhibited tolerance to low chlorine dose (up to 60 mg Cl2 min/L). However, quantitative real-time PCRs revealed that chlorination decreased limited erythromycin or tetracycline resistance genes, with the removal levels of overall erythromycin and tetracycline resistance genes at 0.42 ± 0.12 log and 0.10 ± 0.02 log, respectively. About 40% of erythromycin-resistance genes and 80% of tetracycline resistance genes could not be removed by chlorination. Chlorination was considered not effective in controlling antimicrobial resistance. More concern needs to be paid to the potential risk of antibiotic resistance genes in the wastewater after chlorination.