Occurrence of Bacterial Markers and Antibiotic Resistance Genes in Sub-Saharan Rivers Receiving Animal Farm Wastewaters

Carbapenemase gene blaOXA-48 detected at six freshwater sites in Northern Ireland discharging onto identified bathing locations

Faecal contamination of surface waters has the potential to spread not only pathogenic organisms but also antimicrobial resistant organisms. During the bathing season of 2021, weekly water samples, from six selected coastal bathing locations (n = 93) and their freshwater tributaries (n = 93), in Northern Ireland (UK), were examined for concentrations of faecal indicator bacteria Escherichia coli and intestinal enterococci. Microbial source tracking involved detection of genetic markers from the genus Bacteroides using PCR assays for the general AllBac marker, the human HF8 marker and the ruminant BacR marker for the detection of human, and ruminant sources of faecal contamination. The presence of beta-lactamase genes blaOXA-48, blaKPC, and blaNDM-1 was determined using PCR assays for the investigation of antimicrobial resistance genes that are responsible for lack of efficacy in major broad-spectrum antibiotics. The beta-lactamase gene blaOXA-48 was found in freshwater tributary samples at all six locations. blaOXA-48 was detected in 83% of samples that tested positive for the human marker and 69% of samples that tested positive for the ruminant marker over all six locations. This study suggests a risk of human exposure to antimicrobial resistant bacteria where bathing waters receive at least episodically substantial transfers from such tributaries.

A review of spatial distribution of typical antibiotic resistance genes in marine environment surrounding China

Antibiotic resistance genes (ARGs) have been steadily increasing due to the extensive overuse of antibiotics in the marine environment. Currently, the research considering ARGs distribution in marine ecosystems gains more interest. As the coastal sea has been regarded as one of the most polluted areas by antibiotic contaminants in China. However, no comprehensive review of the spatial distribution of ARGs in marine environment surrounding China. The main objective of this review is to investigate the level, characteristic, and spatial distribution of ARGs in the marine environment (seawater and sediments) surrounding China. Key sea areas, such as Bohai Sea, Yellow Sea, East China Sea, and South China Sea were selected in this review. The marine environment was the reservoir of ARGs, and ARGs in seawater were generally 1 to 2 orders of magnitude higher than that in sediments. Total ARGs were more abundant in the Yellow Sea, followed by the Bohai Sea, the East China Sea, and the South China Sea. This study raises questions regarding the spread and distribution for antibiotic resistance in marine environments.

Antibiotic occurrence, environmental risks, and their removal from aquatic environments using microalgae: Advances and future perspectives

Antibiotic pollution has caused a continuous increase in the development of antibiotic-resistant bacteria and antibiotic-resistant genes (ARGs) in aquatic environments worldwide. Algae-based bioremediation technology is a promising eco-friendly means to remove antibiotics and highly resistant ARGs, and the generated biomass can be utilized to produce value-added products of industrial significance. This review discussed the prevalence of antibiotics and ARGs in aquatic environments and their environmental risks to non-target organisms. The potential of various microalgal species for antibiotic and ARG removal, their mechanisms, strategies for enhanced removal, and future directions were reviewed. Antibiotics can be degraded into non-toxic compounds in microalgal cells through the action of extracellular polymeric substances, glutathione-S-transferase, and cytochrome P450; however, antibiotic stress can alter microalgal gene expression and growth. This review also deciphered the effect of antibiotic stress on microalgal physiology, biomass production, and biochemical composition that can impact their commercial applications.

Risk assessment of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa in environmental water sources: Development of surrogate models for antibiotic resistance genes

The presence of Enterococcus faecium (E. faecium), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa), and the aminoglycoside resistance genes, aac(6')-Ib and aac(6')-aph(2″), was investigated in environmental water sources obtained from informal settlements in the Western Cape (South Africa). Using ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) analysis, E. faecium, K. pneumoniae, and P. aeruginosa were detected in 88.9 %, 100 %, and 93.3 % of the samples (n = 45), respectively, with a significantly higher mean concentration recorded for K. pneumoniae (7.83 × 104 cells/100 mL) over the sampling period. The aac(6')-Ib gene was detected in 95.6 % (43/45) of the environmental water samples [mean concentration of 7.07 × 106 gene copies (GC)/100 mL], while the aac(6')-aph(2″) gene was detected in 100 % (n = 45) of the samples [mean concentration of 6.68 × 105 GC/100 mL]. Quantitative microbial risk assessment (QMRA) subsequently indicated that the risks posed by K. pneumoniae and P. aeruginosa were linked to intentional drinking, washing/bathing, cleaning of the home, and swimming, in the samples collected from the various sampling sites. Surrogate risk assessment models were then designed and applied for Gram-positive [aac(6')-aph(2″) gene] and Gram-negative [aac(6')-Ib gene] pathogens that may exhibit aminoglycoside resistance. The results indicated that only the Gram-negative pathogens posed a risk (>10-4) in all the samples for cleaning of the home and intentional drinking, as well as for washing laundry by hand, garden hosing, garden work, washing/bathing, accidental consumption, and swimming at the stream and marsh sites. Thus, while environmental waters may pose a health risk of exposure to pathogenic bacteria, the results obtained indicate that screening for antibiotic resistant genes, associated with multiple genera/species, could serve as a surrogate model for estimating risks with the target group under investigation.

Molecular epidemiology of antimicrobial resistance in central africa: A systematic review

Background

In Central Africa, it is difficult to tackle antibiotic resistance, because of a lack of data and information on bacterial resistance, due to the low number of studies carried out in the field. To fill this gap, we carried out a systematic review of the various studies, and devised a molecular epidemiology of antimicrobial resistance from humans, animals and the environmental samples.

Method

A systematic search of all publications from 2005 to 2020 on bacterial resistance in Central Africa (Gabon, Cameroon, Democratic Republic of Congo, Central African Republic, Chad, Republic of Congo, Equatorial Guinea, São Tomé and Príncipe, Angola) was performed on Pubmed, Google scholar and African Journals Online (AJOL). All circulating resistance genes, prevalence and genetic carriers of these resistances were collected. The study area was limited to the nine countries of Central Africa.

Results

A total of 517 studies were identified through a literature search, and 60 studies carried out in eight countries were included. Among all articles included, 43 articles were from humans. Our study revealed not only the circulation of beta-lactamase and carbapenemase genes, but also several other types of resistance genes. To finish, we noticed that some studies reported mobile genetic elements such as integrons, transposons, and plasmids.

Conclusion

The scarcity of data poses difficulties in the implementation of effective strategies against antibiotic resistance, which requires a health policy in a 'One Health' approach.

Investigation of antibiotic resistance genotypic and phenotypic characteristics of marine aquaculture fish carried in the Dalian area of China

Due to the long-term and irrational use of antibiotics for the prevention and control of bacterial diseases in aquaculture, antibiotic resistance genes have become a new source of pollution in aquatic products. Factors such as the spread of drug-resistant strains and the horizontal transfer of drug-resistant genes have led to multi-drug resistance in fish-infecting bacteria, which seriously affects the quality and safety of aquatic products. In this study, 50 samples of horse mackerel and puffer fish sold in Dalian aquatic products market and seafood supermarket were collected, and the phenotypic characteristics of the bacteria carried by the fish for drugs such as sulfonamides, amide alcohols, quinolones, aminoglycosides and tetracyclines were tested and analyzed, and the resistance genes carried by fish samples were detected by SYBG qPCR. Our statistical analyses demonstrated that the drug resistance phenotypes and genotypes of bacteria carried by mariculture horse mackerel and puffer fish in the Dalian area of China were complex, and the multi-drug resistance rate reached 80%. Among the examined antibiotics, the resistance rates to cotrimoxazole, tetracycline, chloramphenicol, ciprofloxacin, norfloxacin, levofloxacin, kanamycin, and florfenicol exceeded 50%, whereas the resistance rates to gentamicin and tobramycin were 26 and 16%, respectively. The detection rate of the drug resistance genes tetA, sul1, sul2, qnrA, qnrS, and floR exceeded 70% and all samples carried more than three drug resistance genes. The correlation analysis of drug resistance genes and drug resistance phenotypes showed that the detection of the drug resistance genes sul1, sul2, floR, and qnrD was correlated with the detection of drug resistance phenotypes (p < 0.01). However, the correlation between the resistance genes cmlA, cfr, tetA, qnrA, qnrS, and aac(6')-Ib-cr and the corresponding resistance phenotype was not significant (p > 0.05). In general, our findings indicated that the multi-drug resistance of bacteria carried by marine horse mackerel and puffer fish in the Dalian area was serious. From the perspective of drug resistance rate and drug resistance gene detection rate, the aminoglycosides gentamicin and tobramycin are still considered effective in controlling bacterial infection in marine fish in the study area. Collectively, our findings provide a scientific basis for the management of drug use in mariculture, which can prevent the transmission of drug resistance through the food chain and minimize the associated human health risks.

Antibiotic resistomes and their chemical residues in aquatic environments in Africa

The aquatic environment is a hotspot for the transfer of antibiotic resistance to humans and animals. Several reviews have put together research efforts on the presence and distribution of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic chemical residue (ACRs) in food, hospital wastewater, and even in other aquatic environments. However, these reports are largely focused on data from developed countries, while data from developing countries and especially those in Africa, are only marginally discussed. This review is the first effort that distills information on the presence and distribution of ARGs and ACRs in the African aquatic environments (2012-2021). This review provides critical information on efforts put into the study of ARB, ARGs, and ACRs in aquatic environments in Africa through the lens of the different sub-regions in the continent. The picture provided is compared with those from some other continents in the world. It turns out that the large economies in Africa (South Africa, Nigeria, Tunisia, Kenya) all have a few reports of ARB and ARGs in their aquatic environment while smaller economies in the continent could barely provide reports of these in their aquatic environment (in most cases no report was found) even though they have some reports on resistomes from clinical studies. Interestingly, the frequency of these reports of ARB and ARGs in aquatic environments in Africa suggests that the continent is ahead of the South American continent but behind Europe and Asia in relation to providing information on these contaminants. Common ARGs found in African aquatic environment encode resistance to sulfonamide, tetracycline, β-lactam, and macrolide classes of antibiotics. The efforts and studies from African scientists in eliminating ARB and ARGs from the aquatic environment in Africa are also highlighted. Overall, this document is a ready source of credible information for scientists, policy makers, governments, and regional bodies on ARB, ARGs, and ACRs in aquatic environments in Africa. Hopefully, the information provided in this review will inspire some necessary responses from all stakeholders in the water quality sector in Africa to put in more effort into providing more scientific evidence of the presence of ARB, ARGs, and ACRs in their aquatic environment and seek more efficient ways to handle them to curtail the spread of antibiotic resistance among the population in the continent. This will in turn, put the continent on the right path to meeting the United Nations Sustainable Development Goals #3 and #6, which at the moment, appears to be largely missed by most countries in the continent.

Water Quality Focusing on the Hellenic World: From Ancient to Modern Times and the Future

Water quality is a fundamental issue for the survival of a city, especially on dry land. In ancient times, water availability determined the location and size of villages and cities. Water supply and treatment methods were developed and perfected along with the evolution of urbanization. In Europe, after the fall of the Roman Empire, water supply and sewage systems went through fundamental changes. However, in medieval times, the lack of proper sanitation and low water quality increased the spreading and effects of epidemics. The importance of potable water quality was established during modern times. In Greece, the significance of water filtration and disinfection was not understood until the beginning of the 20th century. Moreover, the beneficial effects of water quality and sanitation on human health and especially on life expectancy are considered. In Greece and other countries, a dramatic increase in life expectancy mainly after the 2nd World War is probably due to the improvement of potable water quality and hygiene conditions. However, since the mid-20th century, new water quality issues have emerged, such as eutrophication, the improvement of water treatment technologies, as well as chemical and microbiological water pollution problems. This study, in addition to the historical evolution of water quality, highlights and discusses the current issues and challenges with regard to the management and protection of water quality, including global changes in population and urbanization, lack of infrastructure, use of nonconventional water resources, spreading of emerging pollutants and contaminants (e.g., antibiotics and microplastics), and climatic variability impacts. Against these, a review of the main proposed strategies and measures is presented and discussed to protect water quality and maintain water supplies for the future. Understanding the practices and solutions of the past provides a lens with which to view the present and future.

A Review of Current Bacterial Resistance to Antibiotics in Food Animals

The overuse of antibiotics in food animals has led to the development of bacterial resistance and the widespread of resistant bacteria in the world. Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in food animals are currently considered emerging contaminants, which are a serious threat to public health globally. The current situation of ARB and ARGs from food animal farms, manure, and the wastewater was firstly covered in this review. Potential risks to public health were also highlighted, as well as strategies (including novel technologies, alternatives, and administration) to fight against bacterial resistance. This review can provide an avenue for further research, development, and application of novel antibacterial agents to reduce the adverse effects of antibiotic resistance in food animal farms.

Occurrence and distribution of Carbapenem-resistant Enterobacterales and carbapenemase genes along a highly polluted hydrographic basin

We determined the distribution and temporal variation of Carbapenem Resistant Enterobacterales (CRE), carbapenemase-encoding genes and other antibiotic resistance genes (ARGs) in a highly polluted river (Lis River; Portugal), also assessing the potential influence of water quality to this distribution. Water samples were collected in two sampling campaigns performed one year apart (2018/2019) from fifteen sites and water quality was analyzed. CRE were isolated and characterized. The abundance of four ARGs (bla_NDM, bla_KPC, tetA, bla_CTX-M), two Microbial Source Tracking (MST) indicators (HF183 and Pig-2-Bac) and the class 1 integrase gene (IntI1) was measured by qPCR. RESULTS: confirmed the poor quality of the Lis River water, particularly in sites near pig farms. A collection of 23 CRE was obtained: Klebsiella (n = 19), Enterobacter (n = 2) and Raoultella (n = 2). PFGE analysis revealed a clonal relationship between isolates obtained in different sampling years and sites. All CRE isolates exhibited multidrug resistance profiles. Klebsiella and Raoultella isolates carried bla_KPC while Enterobacter harbored bla_NDM. Conjugation experiments were successful for only four Klebsiella isolates. All ARGs were detected by qPCR on both sampling campaigns. An increase in ARGs and IntI1 abundances was detected in sites located downstream of wastewater treatment plants. Strong correlations were observed between bla_CTX-M, IntI1 and the human-pollution marker HF183, and also between tetA and the pig-pollution marker Pig-2-bac, suggesting that both human- and animal-derived pollution in the Lis River are a potential source of ARGs. Plus, water quality parameters related to eutrophication and land use were significantly correlated with ARGs abundances. Our findings demonstrated that the Lis River encloses high levels of antibiotic resistant bacteria and ARGs, including CRE and carbapenemase-encoding genes. Overall, this study provides a better understanding on the impacts of water pollution resulting from human and animal activities on the resistome of natural aquatic systems.

Occurrence of toxic metals and their selective pressure for antibiotic-resistant clinically relevant bacteria and antibiotic-resistant genes in river receiving systems under tropical conditions

The co-occurrence of heavy metals, antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) from hospital effluents spreading into the river receiving systems and evaluating associated risks are topics of scientific interest and still under-studied in developing countries under tropical conditions. To understand the selectors of the ARGs, we examined the occurrence of heavy metals (Cr, Co, Ni, Cu, Cd, Pb and Zn), associated ARB (β-lactam-resistant Escherichia coli, β-lactam-resistant Enterobacteriaceae, and carbapenem-resistant Enterobacteriaceae) and ARGs (bla_OXA, bla_CTX-M, bla_IMP, bla_TEM) in water and sediments from two sub-urban rivers receiving urban and hospital effluent waters in the Democratic Republic of the Congo (DRC). High abundances of ARB and ARGs were observed in all sediment samples. All the metal contents correlated negatively with grain size (- 0.94 ≤ r ≤  - 0.54, p < 0.05) except for Ni and positively with organic matter content and total copies of 16 s rRNA (0.42 ≤ r ≤ 0.79, p < 0.05), except for Ni and Zn. The metals had a significant positive correlation with the faecal indicator Enterococcus except for Ni and Cd (0.43 ≤ r ≤ 0.67, p < 0.05). Carbapenem-resistant Enterobacteriaceae correlated negatively with Zn (r =  - 0.44, p < 0.05) and positively with all the rest of toxic metals (0.58 ≤ r ≤ 1.0, p < 0.05). These results suggested that some metals had a great influence on the persistence of ARB and ARGs in sediments. Overall, this study strongly recommends the managing urban wastewater to preserve water resources used for human and agricultural purposes. Additionally, we recommend the utilizing biological indicators (faecal indicator bacteria, ARB, ARGs) when investigating urban wastewater pollutions.

Role of pollution on the selection of antibiotic resistance and bacterial pathogens in the environment

There is evidence that human activity causes pollution that contributes to an enhanced selection of bacterial pathogens in the environment. In this review, we consider how environmental pollution can favour the selection of bacterial pathogens in the environment. We specifically discuss pollutants released into the environment by human activities (mainly human waste) that are associated with the selection for genetic features in environmental bacterial populations that lead to the emergence of bacterial pathogens. Finally, we also identify key pollutants that are associated with antibiotic resistance and discuss possibilities of how to prevent their release into the environment.

Profiles of environmental antibiotic resistomes in the urban aquatic recipients of Sweden using high-throughput quantitative PCR analysis

Antibiotic resistance in aquatic ecosystems presents an environmental health issue worldwide. Urban recipient water quality is susceptible to effluent discharges with antibiotic resistance contaminants and needs to be protected, particularly for those as sources of drinking water production. Knowledge on aquatic resistome profiles in downstream of wastewater treatment plants allows a better understanding of the extent to which antibiotic resistance contaminants emerge and spread in recipient waters, but such information remains very limited in Sweden. The key objective of this study was to determine the resistome profiles of numerous antibiotic resistance genes (ARGs), mobile genetic elements (MGEs) and other genes in urban recipient water systems connected to Sweden's major drinking water reservoir. This was achieved through analysis of surface water samples for 296 genes using high-throughput quantitative PCR arrays. A total of 167 genes were detected in at least one of the samples, including 150 ARGs conferring resistance to 11 classes of antibiotics, 7 integrase MGEs and 9 other genes. There was a spatial difference in the resistome profiles with the greatest average relative abundance of resistance genes observed in the water body of Västerås followed by Uppsala, Stockholm and Eskilstuna, as similar to the general pattern of the antibiotic sales for these regions. ARGs against β-lactams and sulfonamides showed the highest average relative abundance in the studied water bodies, while vancomycin resistance genes were only found in the Uppsala water environment. Generally, the recipient water bodies were detected with higher numbers of genes and greater relative abundances as compared to the upstream sites. Anthropogenic pollution, i.e., wastewater discharge, in the recipient water was also reflected by the finding of intI, sul1 and crAssphage. Overall, this study provided the first quantitative assessment of aquatic environmental resistomes in Sweden, highlighting the widespread of antibiotic resistance contaminants in urban recipient waters.

Antibiotic Resistance and Sewage-Associated Marker Genes in Untreated Sewage and a River Characterized During Baseflow and Stormflow

Since sewage is a hotspot for antibiotic resistance genes (ARGs), the identification of ARGs in environmental waters impacted by sewage, and their correlation to fecal indicators, is necessary to implement management strategies. In this study, sewage treatment plant (STP) influent samples were collected and analyzed using quantitative polymerase chain reaction (qPCR) to investigate the abundance and correlations between sewage-associated markers (i.e., Bacteroides HF183, Lachnospiraceae Lachno3, crAssphage) and ARGs indicating resistance to nine antibiotics (belonging to aminoglycosides, beta-lactams, sulfonamides, macrolides, and tetracyclines). All ARGs, except bla_VIM, and sewage-associated marker genes were always detected in untreated sewage, and ermF and sul1 were detected in the greatest abundances. intl1 was also highly abundant in untreated sewage samples. Significant correlations were identified between sewage-associated marker genes, ARGs and the intl1 in untreated sewage (τ = 0.488, p = 0.0125). Of the three sewage-associated marker genes, the BIO-ENV procedure identified that HF183 alone best maximized correlations to ARGs and intl1 (τ = 0.590). Additionally, grab samples were collected from peri-urban and urban sites along the Brisbane River system during base and stormflow conditions, and analyzed for Escherichia coli, ARGs, the intl1, and sewage-associated marker genes using quantitative polymerase chain reaction (qPCR). Significant correlations were identified between E. coli, ARGs, and intl1 (τ = 0.0893, p = 0.0032), as well as with sewage-associated marker genes in water samples from the Brisbane River system (τ = 0.3229, p = 0.0001). Of the sewage-associated marker genes and E. coli, the BIO-ENV procedure identified that crAssphage alone maximized correlations with ARGs and intl1 in river samples (τ = 0.4148). Significant differences in E. coli, ARGs, intl1, and sewage-associated marker genes, and by flow condition (i.e., base vs. storm), and site types (peri-urban vs. urban) combined were identified (R = 0.3668, p = 0.0001), where percent dissimilarities between the multi-factorial groups ranged between 20.8 and 11.2%. Results from this study suggest increased levels of certain ARGs and sewage-associated marker genes in stormflow river water samples compared to base flow conditions. E. coli, HF183 and crAssphage may serve as potential indicators of sewage-derived ARGs under stormflow conditions, and this merits further investigation. Data presented in this study will be valuable to water quality managers to understand the links between sewage pollution and ARGs in urban environments.

Water Conflicts: From Ancient to Modern Times and in the Future

Since prehistoric times, water conflicts have occurred as a result of a wide range of tensions and/or violence, which have rarely taken the form of traditional warfare waged over water resources alone. Instead, water has historically been a (re)source of tension and a factor in conflicts that start for other reasons. In some cases, water was used directly as a weapon through its ability to cause damage through deprivation or erosion or water resources of enemy populations and their armies. However, water conflicts, both past and present, arise for several reasons; including territorial disputes, fight for resources, and strategic advantage. The main reasons of water conflicts are usually delimitation of boundaries, waterlogging (e.g., dams and lakes), diversion of rivers flow, running water, food, and political distresses. In recent decades, the number of human casualties caused by water conflicts is more than that of natural disasters, indicating the importance of emerging trends on water wars in the world. This paper presents arguments, fights, discourses, and conflicts around water from ancient times to the present. This diachronic survey attempts to provide water governance alternatives for the current and future.

Microbiological safety and antibiotic resistance risks at a sustainable farm under large-scale open-air composting and composting toilet systems

This study evaluated the microbial safety and antibiotic resistance risks of a sustainable ecological farm under large-scale open-air composting (OC) and green composting toilet systems (CT). Samples of livestock manure, compost, soil, vegetables, and rainwater were analysed to determine the best treatment of wastes and risk assessment of land application. Results showed that pathogenic bacteria (PB) in livestock manure was significantly greater than that in the surrounding topsoil, while the distribution of bacteria resistant to amoxicillin (AMX), tetracycline (TC), and amoxicillin-tetracycline (AMX- TC) was the opposite through long-term resistance selection pressure. E. coli and Enterococcus were the dominant pathogens in feces and surrounding soil, respectively, and AMX-resistant bacteria dominated soil, compost, and vegetable samples. Overall, while OC may significantly increase antibiotic resistance and effectively remove fecal PB, CT offers faster consumption with greater antibiotic resistant bacteria (ARB) removal but more PB. Moreover, PB and ARB were concentrated in mature compost, soil in planting areas, vegetables, and rainwater. In farm soil and vegetables, AMX-resistant and AMX-TC-resistant bacterial communities displayed similar composition. These findings may explain the main pathways of PB transmission, migration and accumulation of ARB in farms, and the potential risks to human health through the food chain.

Distribution characteristics and potential risks of heavy metals and antimicrobial resistant Escherichia coli in dairy farm wastewater in Tai'an, China

Heavy metals and antimicrobial resistant bacteria in livestock and poultry environments can cause declines in production and significant economic losses, leading to potential environmental and public health issues. In this study, the heavy metal pollution status of livestock breeding water bodies in the Dawen river basin of Shandong Province in China was evaluated, and a total of 10 heavy metals were measured. In addition, antimicrobial susceptibility tests were conducted for Escherichia coli strains isolated from the water samples. The results showed that among all the metals, copper, zinc, and iron were detected at each sampling point, followed by nickel (detection rate of 95.74%), arsenic (detection rate of 89.36%), selenium (detection rate of 68.09%), lead (detection rate of 27.66%), and mercury (detection rate of 12.77%). Cadmium and hexavalent chromium were not detected. The contents of nine heavy metals were below the existing water standard values in China, whereas the iron pollution index in the water body in the study area was large and may pose a potential risk. A total of 17 E. coli isolates showed different resistance to β-lactams, aminoglycosides, tetracyclines, quinolone antibiotics and chloramphenicol, but were mainly resistant to β-lactams and tetracyclines. The detection rate of the tetA resistance gene was relatively high, indicating the overuse of cephalosporins and tetracyclines. The results of the present study might provide evidence of metal pollution and theoretical basis on the treatment of colibacillosis in the livestock industries.

Longitudinal monitoring of multidrug resistance in Escherichia coli on broiler chicken fattening farms in Shandong, China

The extensive use of antibiotics has, in recent years, caused antimicrobial resistance and multidrug resistance in Escherichia coli to gradually develop into a worldwide problem. These resistant E. coli could be transmitted to humans through animal products and animal feces in the environment, thereby creating a problem for bacterial treatment for humans and animals and resulting in a public health issue. Monitoring the resistance of E. coli throughout the broiler fattening period is therefore of great significance for both the poultry industry and public health. In this longitudinal study, samples were taken from 6 conventional broiler fattening farms in Shandong Province, China, at 3 different times within 1 fattening period. The overall isolation rate of E. coli was 53.04% (375/707). Antibiotic resistance was very common in the E. coli isolated from these farms, and differed for different antibiotics, with ampicillin having the highest rate (92.86%) and cefoxitin the lowest (10.12%). Multidrug resistance was as high as 91.07%. More importantly, both the resistance rate of E. coli to the different drugs and the detection rate of drug resistance genes increased over time. The mobile colistin resistance (mcr-1) gene was detected in 24.40% of the strains, and these strains often carried other drug resistance genes, such as those conferring aminoglycoside, β-lactamase, tetracycline, and sulfonamide resistance. Antimicrobial resistance and drug resistance genes in E. coli were least common in the early fattening stage. The individual detection rates of sul1, sul3, aacC4, aphA3, and mcr-1 were significantly lower (P < 0.05) for the early fattening stage than for the middle and late stages. The rational use of antibiotics, in conjunction with the improvement of the breeding environment during the entire broiler fattening cycle, will be helpful in the development of the poultry industry and the protection of public health.

Occurrence of antibiotic resistance genes and microbial source tracking markers in the water of a karst spring in Germany

The emergence of antimicrobial resistances causes serious public health concerns worldwide. In recent years, the aquatic ecosystem has been recognized as a reservoir for antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). The prevalence of 11 ARGs, active against six antibiotic classes (β-lactams, aminoglycosides, tetracycline, macrolides, trimethoprim, and sulfonamides), was evaluated at a karst spring (Gallusquelle) in Germany, using molecular biological methods. In addition, fecal indicator bacteria (FIB), turbidity, electrical conductivity, spring discharge, and microbial source tracking markers specific for human, horse, chicken, and cow were determined. The ARGs most frequently detected were ermB (42.1%), tet(C) (40.8%), sul2 (39.5%), and sul1 (36.8%), which code for resistance to macrolides, tetracycline and sulfonamides, respectively. After a heavy rain event, the increase in FIB in the spring water was associated with the increase in ARGs and human-specific microbial source tracking (MST) markers. The determined correlations of the microbiological parameters, the observed overflow of a combined sewer overflow basin a few days before the increase of these parameters, and the findings of previous studies indicate that the overflow of this undersized basin located 9 km away from the spring could be a factor affecting the water quality of the karst spring. Our results provide a scientific basis for minimization of the input of fecal pollution and thus ARGs into the karst spring.

Hospital wastewaters: A reservoir and source of clinically relevant bacteria and antibiotic resistant genes dissemination in urban river under tropical conditions

The occurrence and dissemination of antibiotic resistant genes (ARGs) that are associated with clinical pathogens and the evaluation of associated risks are still under-investigated in developing countries under tropical conditions. In this context, cultivable and molecular approaches were performed to assess the dissemination of bacteria and the antibiotic resistance genes in aquatic environment in Kinshasa, Democratic Republic of the Congo. Cultivable approach quantified β-lactam, carbapenem resistant, and total Escherichia coli and Enterobacteriaceae in river sediments and surface waters that receive raw hospital effluents. The molecular approach utilized Quantitative Polymerase Chain Reaction (qPCR) to quantify the total bacteria and the richness of relevant bacteria (Escherichia coli, Enterococcus, and Pseudomonas), and antibiotic resistance genes (ARGs: bla_OXA-48, bla_CTX-M, bla_IMP, bla_TEM) in sediment samples. Statistical analysis were employed to highlight the significance of hospital contribution and seasonal variation of bacteria and ARGs into aquatic ecosystems in suburban municipalities of Kinshasa, Democratic Republic of the Congo. The contribution of hospitals to antibiotic resistance proliferation is higher in the dry season than during the wet season (p < 0.05). Hospital similarly contributed Escherichia coli, Enterococcus, and Pseudomonas and ARGs significantly to the sediments in both seasons (p < 0.05). The organic matter content correlated positively with E. coli (r = 0.50, p < 0.05). The total bacterial load correlated with Enterococcus, and Pseudomonas (0.49 < r < 0.69, p < 0.05). Each ARG correlated with the total bacterial load or at least one relevant bacteria (0.41 < r < 0.81, p < 0.05). Our findings confirm that hospital wastewaters contributed significantly to antibiotic resistance profile and the significance of this contribution increased in the dry season. Moreover, our analysis highlights this risk from untreated hospital wastewaters in developing countries, which presents a great threat to public health.

Impact of anthropogenic activities on the occurrence and distribution of toxic metals, extending-spectra β-lactamases and carbapenem resistance in sub-Saharan African urban rivers

The occurrence and dissemination of toxic metals, antibiotic resistant bacteria and their resistance genes (ARGs) in the aquatic ecosystems of sub-Saharan African countries are still understudied, despite their potential to threat human health and aquatic organisms. In this context, the co-contamination and seasonal distribution of toxic metals and ARG in river sediments receiving untreated urban sewages and hospital effluents from Kinshasa, the capital city of the Democratic Republic of the Congo were investigated. ARGs including β-lactam resistance (bla_CTX-M and bla_SHV), carbapenem resistance (bla_VIM, bla_IMP, bla_KPC, bla_OXA-48 and bla_NDM) and total bacterial load were quantified by using quantitative polymerase chain reaction (qPCR) in total DNA extracted from sediment. The amount of toxic metals in sediments was quantified using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The results highlight high abundance of 16S rRNA and ARGs copy numbers in sediment samples. Strong pollution of rivers by toxic metals was found, with max values (mg kg^-1) of 81.85(Cr), 5.09(Co), 33.84(Ni), 203.46 (Cu), 1055.92(Zn), 324.24(Pb) and 2.96(Hg). Results also highlight the high abundance of bacterial markers (8.06 × 10⁹-2.42 × 10¹² 16S rRNA/g^-1 DS) as well as antibiotic resistance genes (up to 4.58 × 10⁸ ARG. g^-1 DS) in the studied rivers. Significant correlations were observed between (i) metals (except Cd and Hg) and organic matter (R > 0.60, p < 0.05); and (ii) ARGs (except bla_NDM) and 16S rRNA (R > 0.57, p < 0.05) suggesting a tight link between (i) metal contamination and anthropogenic pressure and (ii) microbial contamination of river and dissemination of antibiotic resistance. Results demonstrated that multi-diffuse pollution originating from human activity contribute to the spread of toxic metals and ARGs into the aquatic ecosystems.

Ruminant Fecal Contamination of Drinking Water Introduced Post-Collection in Rural Kenyan Households

In sub-Saharan Africa, many families travel to collect water and store it in their homes for daily use, presenting an opportunity for the introduction of fecal contamination. One stored and one source water sample were each collected from 45 households in rural Kenya. All 90 samples were analyzed for fecal indicator bacteria (E. coli and enterococci) and species-specific contamination using molecular microbial source tracking assays. Human (HF183), avian (GFD), and ruminant (BacR) contamination were detected in 52, two, and four samples, respectively. Stored water samples had elevated enterococci concentrations (p < 0.01, Wilcoxon matched pairs test) and more frequent BacR detection (89% versus 27%, p < 0.01, McNemar's exact test) relative to source water samples. fsQCA (fuzzy set qualitative comparative analysis) was conducted on the subset of households with no source water BacR contamination to highlight combinations of factors associated with the introduction of BacR contamination to stored water supplies. Three combinations were identified: (i) ruminants in the compound, safe water extraction methods, and long storage time, (ii) ruminants, unsafe water extraction methods, and no soap at the household handwashing station, and (iii) long storage time and no soap. This suggests that multiple pathways contribute to the transmission of ruminant fecal contamination in this context, which would have been missed if data were analyzed using standard regression techniques.