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Sample sources that yielded the Shiga toxin-producing E. coli strains, examined in the present study. Wildlife (32%), watersheds (24%), leafy vegetables (22%), livestock (18%), other vegetables (1%), sediment (1%), soil (1%), and fruit (1%). https://doi.org/10.1371/journal.pone.0187827.g001
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The rapid spreading of polymyxin E (colistin) resistance among bacterial strains through the horizontally transmissible mcr-1 and mcr-2 plasmids has become a serious concern. The emergence of these genes in Shiga toxin-producing Escherichia coli (STEC), a group of human pathogenic bacteria was even more worrisome, urging us to investigate the preva...
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Escherichia coli is considered one of the most common agents associated with neonatal diarrhea in piglets. The aim of this work was to characterize the pathogenic and antimicrobial resistance (AMR) profiles of 122 E. coli strains isolated from pigs suffering diarrhea (n = 94) and pigs without diarrhea (n = 28) of 24 farms in Spain. Virulence factor...
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... Very low prevalence of mcr-1 is consistent with findings in similar studies, such as a screen of 1,000 environmental Shiga toxinproducing E. coli isolates in the agricultural region of California, identified by PCR that did not detect mcr-1 or mcr-2. 9 Similarly, a screen of cecal contents in >2,000 food animals identified only 2 samples (<0.1%) positive for mcr-1. 10 Our report provides the first assessment of mcr-1 dissemination in North Carolina. ...
... Mcr-1 and mcr-2 have been detected in pork carcasses, chicken meat and mutton in Belgium, Brazil and India respectively (Garciagraells et al., 2018;Ghafur et al., 2019;Monte et al., 2017). In contrast, none of the 1000 STEC isolates collected from 2006 through 2014 from livestock, wildlife, produce, soil and water samples from a major food-producing region of California, tested positive for mcr-1 or mcr-2 (Mavrici et al., 2017). Colistin has been widely used as a growth promoter in Belgium, India, China and Brazil, but not in the US (Sun et al., 2017), which could account for the detection of colistin resistance genes in those countries. ...
A circular food system is one in which food waste is processed to recover plant nutrients and returned to the soil to enable the production of more food, rather than being diverted to landfill or incineration. The approach may be used to reduce energy and water use in food production and contribute to the sustainability of the system. Anaerobic digestion and composting are common food waste treatment technologies used to stabilize waste and produce residual materials that can replenish the soil, thus contributing to a circular food system. This approach can only be deemed safe and feasible, however, if food waste is uncontaminated or any contaminants are destroyed during treatment. This review brings together information on several contaminant classes at different stages of the food supply chain, their possible sources, and their fates during composting and digestion. The main aim is to identify factors that could impede the transition towards a safe, reliable and efficient circular food system. We investigated heavy metals, halogenated organic compounds, foodborne pathogens and antibiotic resistance genes (ARGs) in the food system and their fates during digestion and composting. Production and processing stages were identified as major entry points for these classes of contaminants. Heavy metals and foodborne pathogens pose less risk in a circular system than halogenated organics or antibiotic resistance. Given the diversity of properties among halogenated organic compounds, there is conflicting evidence about their fate during treatment. There are relatively few studies on the fate of ARGs during treatment, and these have produced variable results, indicating a need for more research to clarify their fate in the final products. Repeated land application of contaminated food waste residuals can increase the risk of accumulation and jeopardize the safety of a circular food system. Thus, careful management of the system and research into the fate of the contaminants during treatment is needed.
... Mcr-1 and mcr-2 have been detected in swine cecae, pork carcasses, chicken meat and mutton in the Belgium, Brazil and India respectively (Garcia-graells et al., 2018;Ghafur et al., 2019;Meinersmann, Ladely, Plumblee, Cook, & Thacker, 2017;Monte et al., 2017). In contrast, 1000 STEC isolates collected from 2006 through 2014 from livestock, wildlife, produce, soil and water samples from a major food-producing region of California, and that were screened for mcr-1 and mcr-2 genes tested negative (Mavrici, Yambao, Lee, Quiñones, & He, 2017). In the US colistin has never been used in animals whereas colistin has been widely used as growth promoter in India, China and Brazil (Sun et al., 2017). ...
... Plasmid-borne mcr-1-mediated resistance has recently spread throughout the world (Caniça et al., 2019). No mcr-1 was detected in any of our samples, which was similar to the results of a study by Mavrici et al., (2017) who screened 1000 E. coli isolates obtained from wildlife, produce and environmental samples for mcr-1, and all came out negative in their study. ...
... and 2 poultry meat samples) A=(Del Collo et al., 2017), B=(Mavrici et al., 2017), C=(Schwaiger et al., 2011), D=(Adenipekun et al., 2019), E=(Larrañaga et al., 2018), F=(Iwamoto et al., 2017), G=(Bosilevac et al., 2009), H=(Glenn et al., 2013), I=(Vikram et al., 2018), J=(Folster et al., 2012), K=(Aslam, Diarra, Service, & Rempel, 2009), L=(Sharma et al., 2019), M=(Sjölund-Karlsson et al., 2013), N=(Garcia-graells et al., 2018), O=(Monte et al., 2017), P= (Y.-Y.Liu et al., 2016) and Q=(Ghafur et al., 2019). ...
About a third of the food produced annually is wasted. Food waste recycling can be a way to close the loop and attain a more sustainable food system, however, the system must be carefully monitored and managed to avoid the introduction and build-up of contaminants. To study the potential presence of contaminants in food waste, source-separated food waste was collected and screened for five classes of contaminants (physical contaminants, heavy metals, halogenated organic contaminants, pathogens, and antibiotic resistance genes) from two separate regulatory environments (voluntary vs mandated food separation). The regulatory environment did not affect the level of contamination, except there was more physical contamination in Maine, where food waste diversion is not mandated. Fifty-seven percent of samples had some form of non-compostable waste. Most of the heavy metals tested were not detected. Copper and zinc were detected in most samples but were always below the most stringent global standards for compost. Some samples had detectable halogenated organics, which is cause for concern because some are known to accumulate in the food chain. Foodborne pathogens were seldom detected and should be killed during treatment, but this could pose a risk to collectors and haulers. Antibiotic resistance genes were detected in most samples. This could jeopardize the utility of antibiotics used to fight infections. More research is needed to determine the fate of antibiotic resistance genes and halogenated organics during treatment, and the risk of their accumulation in a circular food system.
... Therefore, surveillance of plasmid-mediated colistin resistance in botanical ecosystem is warranted in these continents. Nevertheless, it is worth noting that no mcr-1 or mcr-2-positive strain was detected among 240 shigatoxin-producing E. coli isolates from vegetables/fruits in the US [139], and no mcr-1-carrying strain was detected among COL-resistant enterobacterial isolates from vegetables in Brazil [96]. ...
... This plasmid was further proven to potentially reduce the virulence of MGCB by injecting an~1 × 10 5 CFU of ST34 K. pneumoniae strains into Galleria mellonella larvae and observing significantly lowered mortality. It is worth mentioning that none of the studies on COL resistance among isolates from reptiles such as in turtles in Brazil, [96], reptiles in the US [139], and snake in Taiwan [153], detected any mcr-carrying strain. This warrants further surveillance since reptiles make contact with aquatic and terrestrial ecosystems. ...
The emergence and spread of mobile colistin (COL) resistance (mcr) genes jeopardize the efficacy of COL, a last resort antibiotic for treating deadly infections. COL has been used in livestock for decades globally. Bacteria have mobilized mcr genes (mcr-1 to mcr-9). Mcr-gene-containing bacteria (MGCB) have disseminated by horizontal/lateral transfer into diverse ecosystems, including aquatic, soil, botanical, wildlife, animal environment, and public places. The mcr-1, mcr-2, mcr-3, mcr-5, mcr-7, and mcr-8 have been detected in isolates from and/or directly in environmental samples. These genes are harboured by Escherichia coli, Enterobacter, Klebsiella, Proteus, Salmonella, Citrobacter, Pseudomonas, Acinetobacter, Kluyvera, Aeromonas, Providencia, and Raulotella isolates. Different conjugative and non-conjugative plasmids form the backbones for mcr in these isolates, but mcr have also been integrated into the chromosome of some strains. Insertion sequences (IS) (especially ISApl1) located upstream or downstream of mcr, class 1-3 integrons, and transposons are other drivers of mcr in the environment. Genes encoding multi-/extensive-drug resistance and virulence are often co-located with mcr on plasmids in environmental isolates. Transmission of mcr to/among environmental strains is clonally unrestricted. Contact with the mcr-containing reservoirs, consumption of contaminated animal-/plant-based foods or water, international animal-/plant-based food trades and travel, are routes for transmission of MGCB.
... The highest detection rate was recorded in chicken farms, where 97 per cent of samples were contaminated (Yang et al. 2017;Chen 2018). This may be concerning, however when you link the report with that of similar colistin resistant bacteria in the environment of California and Brazil (Mavrici et al. 2017;Rossi et al. 2017), it can be seen as a problem of international proportions. ...
The development of hormonal anabolic steroids and antibiotics to regulate the metabolism and disease status of humans has led to the evolution of therapeutic reagents designed to promote the growth of domestic farm animals over the second half of the 20th century. The most effective regime of hormones involved a combination of oestrogen and testosterone analogues carefully formulated into solid implants administered into the ear. These reagents can remain effective for up to 400 days depending on the regime of treatment. Provided animals are well fed, growth rates can be improved by over 15%. They can also be used to modify the degree of carcass fatness, which depends on the breed of livestock. In contrast antibiotics are sourced from a wide spectrum of biological resources dominated by bacteria, fungi and mould, in which they serve as protective molecules from other bacteria. They can be used at low levels as feed additives to selectively decrease the microbial load in the gastrointestinal tract and therefore increase the efficiency of feed utilisation by as much as 25%. Together with their over-prescription in human medicine this practice has accelerated the process of microbial resistance. The complement of genes responsible for the multiple resistance mechanisms including the synthesis of antibiotic targeted enzymes are easily transferred across species including humans through zoonotic transfer. Our increased awareness of the potential adverse environmental impacts of HGP’s and the ever-present risk of developing populations of antibiotic resistant bacteria has dictated that we investigate alternative strategies to boost the growth efficiency of our commercial livestock species. Failure to do so will compromise our ability to supply the world’s ever-increasing demand for high quality animal protein.
... Other genes have been identified as conferring resistance to polymyxin, such as mcr-1 to mcr-7 (E. Coli and K. pneumonia) [25][26][27]. ...
... Another polymyxin repulsion mechanism results from adding D-alanine (D-Ala) to teichoic acids, thereby increasing net positive charge due to the dlt-ABCD genes. Adding D-Ala to an OM has been described in other bacteria, regulating graXSR, dra/dlt, liaSR and CiaR operons (Staphylococcus aureus, Bordetella pertussis, Streptococcus gordonii, Listeria monocytogenes, Group B Streptococcus) [26,27]. Additional mechanisms have been described inducing modifications on cell surface regarding electrostatic repulsion of colistin, such as lipid A deacylation and hydroxylation by genes encoding Pag, PagL, LpxM and LpxO enzymes and decreasing membrane fluidity/permeability [25]. ...
Antimicrobial resistance to antibiotic treatment has significantly increased during recent years, causing this to become a worldwide public health problem. More than 70% of pathogenic bacteria are resistant to at least one of the currently used antibiotics. Polymyxin E (colistin) has recently been used as a "last line" therapy when treating Gram-negative multi-resistant bacteria. However, little is known about these molecules' pharmacological use as they have been discontinued because of their high toxicity. Recent research has been focused on determining colistimethate sodium's pharmacokinetic parameters to find the optimal dose for maintaining a suitable benefit-risk balance. This review has thus been aimed at describing the use of colistin on patients infected by multi-drug resistant bacteria and the importance of measuring this drug's plasma levels in such patients.
... Genotypic methods include conventional PCR, real-time PCR and whole genome sequencing (WGS). PCR methods were used to amplify mcr genes mediating resistance to colistin [23][24][25] . These methods are faster than the phenotypic tests without an initial culturing step. ...
Abstract The recent discovery and rapid spread of mobile colistin-resistant gene, mcr-1, among bacteria isolated from a broad range of sources is undermining our ability to treat bacterial infections and threatening human health and safety. To prevent further transfer of colistin resistance, practical and reliable methods for mcr-1-containing bacteria are need. In this study, standards and novel polyclonal and monoclonal antibodies (mAbs) against MCR-1 were developed. Among nine mAbs, three were MCR-1 specific and six cross-reacted with both MCR-1 and MCR-2. A sandwich enzyme-linked immunosorbent assay (ELISA) was established using the polyclonal antibody as a capturer and the mAb MCR-1-7 as a detector. The assay had a limit of detection of 0.01 ng/mL for MCR-1 and 0.1 ng/mL for MCR-2 in buffer with coefficients of variation (CV) less than 15%. When applied to ground beef, chicken and pork, this ELISA identified samples inoculated with less than 0.4 cfu/g of meat, demonstrating its strong tolerance to complex food matrices. To our knowledge, this is the first immunoassay developed for MCR-1 and MCR-2. It should be useful for prompt and reliable screening of meat samples contaminated with plasmid-borne colistin-resistant bacteria, thus reducing human risk of foodborne infections with possibly no antibiotic treatment options.
... For pathogenic E. coli, one study assessed the prevalence of plasmid-borne colistin resistance genes mcr1/mcr2 in STEC E. coli from the United States; not a single positive isolate was found in 1000 strains from different sources, including about 230 isolates from vegetables (Mavrici et al., 2017). ...
In recent years, vegetables gain consumer attraction due to their reputation of being healthy in combination with low energy density. However, since fresh produce is often eaten raw, it may also be a source for foodborne illness. The presence of antibiotic-resistant bacteria might pose a particular risk to the consumer. Therefore, this review aims to present the current state of knowledge concerning the exposure of humans to antibiotic-resistant bacteria via food of plant origin for quantitative risk assessment purposes. The review provides a critical overview of available information on hazard identification and characterization, exposure assessment, and risk prevention with special respect to potential sources of contamination and infection chains. Several comprehensive studies are accessible regarding major antimicrobial-resistant foodborne pathogens (e.g., Salmonella spp., Listeria spp., Bacillus cereus, Campylobacter spp., Escherichia coli) and other bacteria (e.g., further Enterobacteriaceae, Pseudomonas spp., Gram-positive cocci). These studies revealed vegetables to be a potential-although rare-vector for extended-spectrum beta-lactamase-producing Enterobacteriaceae, mcr1-positive E. coli, colistin- and carbapenem-resistant Pseudomonas aeruginosa, linezolid-resistant enterococci and staphylococci, and vancomycin-resistant enterococci. Even if this provides first clues for assessing the risk related to vegetable-borne antimicrobial-resistant bacteria, the literature research reveals important knowledge gaps affecting almost every part of risk assessment and management. Especially, the need for (comparable) quantitative data as well as data on possible contamination sources other than irrigation water, organic fertilizer, and soil becomes obvious. Most crucially, dose-response studies would be needed to convert a theoretical "risk" (e.g., related to antimicrobial-resistant commensals and opportunistic pathogens) into a quantitative risk estimate.
Food waste recycling is needed to create a more sustainable, circular food system; however, the process must be carefully managed to avoid the introduction and build-up of contaminants. We collected and screened source-separated food waste for five classes of contaminants (physical contaminants, heavy metals, halogenated organics, pathogens and antibiotic resistance genes) from two regulatory environments (voluntary vs mandated food separation) to quantify contamination. Physical contamination was frequently found; 57% of samples contained non-compostable waste. Most heavy metals were not detected, and although copper and zinc were present in most samples, they were always below the most stringent global standards for compost. Some samples had detectable halogenated organics, including perfluoroalkyl substances (PFAS), which is cause for concern because some of these accumulate in the food chain. PFBA was detected in 60%, PFHxS in 8% and PFNA in 4% of samples tested. The pathogen Salmonella was present in 3% (2/71) and L. monocytogenes in 11% (8/71) of samples. Shiga toxin-producing E. coli was not detected. Next generation sequencing showed the presence of several genera that contain foodborne pathogens, most commonly Yersinia. Antibiotic resistance genes tet(M) and blaTEM were present in 96% and 97% of samples respectively, however the last-resort colistin resistance gene mcr-1 was not detected. Overall contamination in our source-separated samples was low, with the exception of some antibiotic resistance genes, however our processing method might have underestimated packaging-associated contamination. Regulatory environment did not affect contamination, but carbon, nitrogen phosphorus, calcium, copper, tet (M), and physical contamination varied by source type.
This paper describes the results and outcomes of a survey conducted to investigate the presence of mcr-1 in 5169 domestic animal-origin samples collected by the USDA-Food Safety and Inspection Service between October 2018 and May 2019. Samples from chicken rinse (N = 1787), ground beef (N = 1369), beef trim (N = 1057), poultry (N = 363), raw pork (N = 416) and catfish (N = 177) were enriched in non-selective media and transferred to 96 well plates with a selection medium containing CaCl2, colistin and vancomycin. A novel ELISA was used to screen for the mcr-1 gene product (MCR-1). Only a single colistin resistant Escherichia coli carrying a mcr-1 gene was isolated from raw pork with a MIC of 8 mg/L, which resulted in an overall mcr-1 presence in raw pork of 0.24% and less than 0.02% in the total samples tested. This study represents the first large-scale investigation of mcr-1 in the U.S. meat, poultry, and catfish. Further examination of the positive isolate, Escherichia coli 2492 (EC2492), by whole genome sequencing revealed that this strain contained a 4.8 Mb chromosome and six plasmids. The mcr-1 gene was located on an IncI2 type plasmid and other five resistance genes, tetA, tetR, sul2, aph (3”)-Ib and aph (6)-Id identified were located on an IncB/O/K/Z plasmid. In silico analysis assigned EC2492 to ST101 and serotype O54:H21. In conclusion, while the survey results indicated that mcr-1 is rare in the U.S. animal derived foods, that one positive isolate was found suggests that continued vigilance to minimize further spread of mobile colistin resistance is warranted.
