Seasonal variations in antibiotic resistance gene transport in the Almendares River, Havana, Cuba

Numerous studies have quantified antibiotic resistance genes (ARG) in rivers and streams around the world, and significant relationships have been shown that relate different pollutant outputs and increased local ARG levels. However, most studies have not considered ambient flow conditions, which can vary dramatically especially in tropical countries. Here, ARG were quantified in water column and sediment samples during the dry- and wet-seasons to assess how seasonal and other factors influence ARG transport down the Almendares River (Havana, Cuba). Eight locations were sampled and stream flow estimated during both seasons; qPCR was used to quantify four tetracycline, two erythromycin, and three beta-lactam resistance genes. ARG concentrations were higher in wet-season versus dry-season samples, which combined with higher flows, indicated much greater ARG transport downstream during the wet-season. However, water column ARG levels were more spatially variable in the dry-season than the wet-season, with the proximity of waste outfalls strongly influencing local ARG levels. Results confirm that dry-season sampling provides a useful picture of the impact of individual waste inputs on local stream ARG levels, whereas the majority of ARGs in this tropical river were transported downstream during the wet-season, possibly due to re-entrainment of ARG from sediments

Agricultural contamination impacts antibiotic resistance gene abundances in river bed sediment temporally

Kewaunee County, Wisconsin is an agricultural area dominated by concentrated animal feeding operations and manure fertilized cropland. The objective of this study was to characterize chemical and antibiotic resistance gene (ARG) profiles of 20 surface water locations in Kewaunee County to better understand relationships between agricultural contamination and ARG abundance over one year. Surface water (n = 101) and bed sediment (n = 93) were collected from 20 sites during five timepoints between July 2016 and May 2017. Samples were analyzed for six genes (erm(B), tet(W), sul1, qnrA, intI1 and 16S rRNA) and water chemistry and pollution indicators. qnrA, intI1 and sul1 genes in surface water were significantly higher than erm(B) and tet(W); however, no difference was present in sediment samples. Redundancy analysis identified positive correlations of nitrate, Escherichia coli, and coliforms with tet(W) and intI1 genes in sediment and intI1, sul1 and tet(W) genes in water. Temporal patterns of ARG abundance were identified with significantly higher gene abundances found in sediment during Kewaunee County\u27s manure fertilization period; however, surface water patterns were not distinct. Together, these results suggest Kewaunee County sediments serve as a site of accumulation for non-point source agricultural pollution and ARGs on a temporal scale associated with manure fertilization

Antibiotic Resistance Gene Abundances Correlate with Metal and Geochemical Conditions in Archived Scottish Soils

The vast majority of antibiotic resistant genes (ARG) acquired by human pathogens have originated from the natural environment. Therefore, understanding factors that influence intrinsic levels of ARG in the environment could be epidemiologically significant. The selection for metal resistance often promotes AR in exposed organisms; however, the relationship between metal levels in nature and the intrinsic presence of ARG has not been fully assessed. Here, we quantified, using qPCR, the abundance of eleven ARG and compared their levels with geochemical conditions in randomly selected soils from a Scottish archive. Many ARG positively correlated with soil copper levels, with approximately half being highly significant (p<0.05); whereas chromium, nickel, lead, and iron also significantly correlated with specific ARG. Results show that geochemical metal conditions innately influence the potential for AR in soil. We suggest soil geochemical data might be used to estimate baseline gene presence on local, regional and global scales within epidemiological risk studies related to AR transmission from the environment

The effect of combined sewer overflow (CSO) on the abundance of antibiotic resistant bacteria in the James River

Antibiotics have been used to treat bacterial infections worldwide since their discovery in the early 20th century and are vital to human health. Unfortunately, the heavy use of antibiotics has led to the increased natural selection of antibiotic resistant bacteria. In urban rivers, the spread of resistance resistance is through through the direct acquisition of resistance genes by either either either cell-to -cell contact or DNA uptake via a process called horizontal gene transfer transfer(HGT) 2.HGT, resistance genes, and resistant bacteria are in greater abundance in wastewater systems, and are released into the environment in wastewater plant effluent2,3. One problematic method of wastewater treatment, used in over over 750 cities in the US, is the Combined Sewer System System(CSS) 4.This collects the water from both rainfall and sewage for treatment at a single facility.Occasionally when it rains, the treatment plant exceeds capacity and the combined untreated effluent enters the river in what is called a CSO (Combined Sewer Overflow) event. Some studies have found that antibiotic resistance genes can be more abundant in river water water affected by wastewater treatment effluent and correlated with CSO events events 7

Antibiotic Resistance Gene Abundances Associated with Waste Discharges to the Almendares River near Havana, Cuba

Considerable debate exists over the primary cause of increased antibiotic resistance (AR) worldwide. Evidence suggests increasing AR results from overuse of antibiotics in medicine and therapeutic and nontherapeutic applications in agriculture. However, pollution also can influence environmental AR, particularly associated with heavy metal, pharmaceutical, and other waste releases, although the relative scale of the “pollution” contribution is poorly defined, which restricts targeted mitigation efforts. The question is “where to study and quantify AR from pollution versus other causes to best understand the pollution effect”. One useful site is Cuba because industrial pollution broadly exists; antibiotics are used sparingly in medicine and agriculture; and multiresistant bacterial infections are increasing in clinical settings without explanation. Within this context, we quantified 13 antibiotic resistance genes (ARG; indicators of AR potential), 6 heavy metals, 3 antibiotics, and 17 other organic pollutants at 8 locations along the Almendares River in western Havana at sites bracketing known waste discharge points, including a large solid waste landfill and various pharmaceutical factories. Significant correlations (p < 0.05) were found between sediment ARG levels, especially for tetracyclines and β-lactams (e.g., tet(M), tet(O), tet(Q), tet(W), blaOXA), and sediment Cu and water column ampicillin levels in the river. Further, sediment ARG levels increased by up to 3 orders of magnitude downstream of the pharmaceutical factories and were highest where human population densities also were high. Although explicit links are not shown, results suggest that pollution has increased background AR levels in a setting where other causes of AR are less prevalent

The effect of heavy metals on antibiotic resistance in the environment

Copper concentrations influenced tetracycline and (Sb (Blactamase resistance gene abundances in both soils and simulated wastewater activated-sludge treatment process. Results suggest that copper discharged to wastewater and the environment increase resistance genes. Additionally surface-water microcosms were used to determine whether copper concentration enhanced retention of antibiotic resistance genes released by wastewater treatment. While no selection effect was observed, further work is still needed. Effect exhorted by metals on antibiotic resistance is not novel; however, its role in the environment could play a more significant role in the clinical problem than anticipated. Agencies, such as World Health Organisation, call for further investigations to reduce antibiotic resistance in the environment; this thesis highlights how metals, particularly, contributes to the problemAntibiotic resistance is a significant clinical problem, with bacterial infections becoming increasingly difficult to treat. Efforts, such as reducing the use of antibiotics, have proved unsuccessful, and we now face the prospect of a future without antibiotics. The natural environment acts as a reservoir for resistance genes. The selection and maintenance of resistance could counteract clinical efforts to reduce antibiotic resistance. Heavy metals have been linked to antibiotic resistance by genetic mechanisms whereby metals potentially select for and maintain antibiotic resistance, even in the absence of the antibiotic itself. Here, the role of heavy metals in enhancing, or maintaining, antibiotic resistance in the environment is investigated. Background levels of metals in soil were found to correlate to antibiotic resistance gene abundances, implying the effect heavy metals in the environment have on antibiotic resistance is more intrinsic than anticipated. Using controlled microcosm studies, the influence of pollution levels on antibiotic resistance was further investigated. Copper concentrations influenced tetracycline and β lactamase resistance gene abundances in both soils and simulated wastewater activated-sludge treatment process. Results suggest that copper discharged to wastewater and the environment increase resistance genes. Additionally surface-water microcosms were used to determine whether copper concentration enhanced retention of antibiotic resistance genes released by wastewater treatment. While no selection effect was observed, further work is still needed. Effect exhorted by metals on antibiotic resistance is not novel; however, its role in the environment could play a more significant role in the clinical problem than anticipated. Agencies, such as World Health Organisation, call for further investigations to reduce antibiotic resistance in the environment; this thesis highlights how metals, particularly, contributes to the problem.Antibiotic resistance is a significant clinical problem, with bacterial infections becoming increasingly difficult to treat. Efforts, such as reducing the use of antibiotics, have proved unsuccessful, and we now face the prospect of a future without antibiotics. The natural environment acts as a reservoir for resistance genes. The selection and maintenance of resistance could counteract clinical efforts to reduce antibiotic resistance. Heavy metals have been linked to antibiotic resistance by genetic mechanisms whereby metals potentially select for and maintain antibiotic resistance, even in the absence of the antibiotic itself. Here, the role of heavy metals in enhancing, or maintaining, antibiotic resistance in the environment is investigated. Background levels of metals in soil were found to correlate to antibiotic resistance gene abundances, implying the effect heavy metals in the environment have on antibiotic resistance is more intrinsic than anticipated. Using controlled microcosm studies, the influence of pollution levels on antibiotic resistance was further investigated. Copper concentrations influenced tetracycline and β lactamase resistance gene abundances in both soils and simulated wastewater activated-sludge treatment process. Results suggest that copper discharged to wastewater and the environment increase resistance genes. Additionally surface-water microcosms were used to determine whether copper concentration enhanced retention of antibiotic resistance genes released by wastewater treatment. While no selection effect was observed, further work is still needed. Effect exhorted by metals on antibiotic resistance is not novel; however, its role in the environment could play a more significant role in the clinical problem than anticipated. Agencies, such as World Health Organisation, call for further investigations to reduce antibiotic resistance in the environment; this thesis highlights how metals, particularly, contributes to the problem

The effect of combined sewer overflows on the abundance of antibiotic resistance genes and bacteria in the James River

Antibiotic resistance is a major threat to human health. Clinical situations are the main focus for antibiotic resistance research, but understanding the spread of resistance in the environment is also vital. A major contributor to this spread is wastewater from combined sewer overflow (CSO) events. The effect of CSO events on antibiotic resistance in the James River near Richmond, Virginia was studied using genomic and microbiological approaches. The abundance of genes associated with resistance to quinolones (qnrA) and tetracycline (tetW) was strongly correlated with the presence of fecal indicator bacteria (E. coli abundance) as well as total nitrogen and phosphorus loads, which suggests an anthropogenic source of these genes. Abundance of the blaTEM gene, which confers resistance to β-lactam antibiotics, was elevated during CSO events and increased with precipitation and river discharge. Bacteria isolated during a CSO event were resistant to more antibiotics and had higher multi-drug resistance when compared to isolates from a non-event. This study demonstrated that CSO events are contributing to the spread of antibiotic resistance

Natural Antibiotic Resistance and Contamination by Antibiotic Resistance Determinants: The Two Ages in the Evolution of Resistance to Antimicrobials

Work in our laboratory is supported by grants BIO2008-00090 from the Spanish Ministry of Science and Innovation and KBBE-227258 (BIOHYPO), HEALTH-F3-2011-282004 (EVOTAR), and HEALTH-F3-2010-241476 (PAR) from European Union.Peer reviewedPeer Reviewe

Appearance of β-lactam resistance genes in agricultural soils and clinical isolates over the 20th century

Debate exists about whether agricultural versus medical antibiotic use primarily drives increasing antibiotic resistance (AR) across nature. Both sectors have been historically inconsistent at antibiotic stewardship and, as a result, acquired bacterial AR has progressively increased over the 20th century. The question is which sector has most influenced changes in acquired AR. To examine this question, we quantified four broad spectrum β-lactam AR (ARG; blaTEM, blaSHV, blaOXA and blaCTX-M) and class 1 integron genes (int1) in soils archived since 1894 from Askov Experimental Station, Denmark. ARG levels were significantly higher in post-1940 soils that only received manure (M) versus inorganic fertilisers (IF) (paired-t test; p < 0.001). However, first appearance of each ARG varied over historic time; blaTEM and blaSHV between 1963 and 1974, blaOXA slightly later, and blaCTX-M in 1989, dates that parallel appearance of each ARG in hospital isolates, suggesting their parallel occurrence in animal manure and human patients. It is not possible to determine whether farm versus hospital AR appeared first, but archive data imply they are mutually influential. Interestingly, levels of β-lactam ARGs in the M soils, especially blaCTX-M, declined since the mid-1990s, which aligns with reduced non-therapeutic antibiotic use in Danish agriculture. These data suggest improved antibiotic stewardship can reduce soil ARG reservoirs, although it also shows reduced manure applications to agricultural soils should be included in prudent stewardship programmes