Transient intestinal carriage after ingestion of antibiotic-resistant Enterococcus faecium from chicken and pork

Chagas disease is related to structural changes of the gut microbiota in adults with chronic infection (TRIPOBIOME Study)

BACKGROUND

The implications of the gut microbial communities in the immune response against parasites and gut motility could explain the differences in clinical manifestations and treatment responses found in patients with chronic Chagas disease.

METHODOLOGY/PRINCIPAL FINDINGS

In this pilot prospective cross-sectional study, we included 80 participants: 29 with indeterminate CD (ICD), 16 with cardiac CD (CCD), 15 with digestive CD (DCD), and 20 controls without CD. Stool was collected at the baseline visit and faecal microbial community structure DNA was analyzed by whole genome sequencing. We also performed a comprehensive dietary analysis. Ninety per cent (72/80) of subjects were of Bolivian origin with a median age of 47 years (IQR 39-54) and 48.3% (29/60) had received benznidazole treatment. There were no substantial differences in dietary habits between patients with CD and controls. We identified that the presence or absence of CD explained 5% of the observed microbiota variability. Subjects with CD exhibited consistent enrichment of Parabacteroides spp, while for Enterococcus hirae, Lactobacillus buchneri and Megamonas spp, the effect was less clear once excluded the outliers values. Sex, type of visceral involvement and previous treatment with benznidazole did not appear to have a confounding effect on gut microbiota structure. We also found that patients with DCD showed consistent Prevotella spp enrichment.

CONCLUSIONS

We found a detectable effect of Chagas disease on overall microbiota structure with several potential disease biomarkers, which warrants further research in this field. The analysis of bacterial diversity could prove to be a viable target to improve the prognosis of this prevalent and neglected disease.

Antibiotic Resistance among Gastrointestinal Bacteria in Broilers: A Review Focused on Enterococcus spp. and Escherichia coli

Chickens can acquire bacteria at different stages, and bacterial diversity can occur due to production practices, diet, and environment. The changes in consumer trends have led to increased animal production, and chicken meat is one of the most consumed meats. To ensure high levels of production, antimicrobials have been used in livestock for therapeutic purposes, disease prevention, and growth promotion, contributing to the development of antimicrobial resistance across the resident microbiota. Enterococcus spp. and Escherichia coli are normal inhabitants of the gastrointestinal microbiota of chickens that can develop strains capable of causing a wide range of diseases, i.e., opportunistic pathogens. Enterococcus spp. isolated from broilers have shown resistance to at least seven classes of antibiotics, while E. coli have shown resistance to at least four. Furthermore, some clonal lineages, such as ST16, ST194, and ST195 in Enterococcus spp. and ST117 in E. coli, have been identified in humans and animals. These data suggest that consuming contaminated animal-source food, direct contact with animals, or environmental exposure can lead to the transmission of antimicrobial-resistant bacteria. Therefore, this review focused on Enterococcus spp. and E. coli from the broiler industry to better understand how antibiotic-resistant strains have emerged, which antibiotic-resistant genes are most common, what clonal lineages are shared between broilers and humans, and their impact through a One Health perspective.

Tracking Antimicrobial Resistant E. coli from Pigs on Farm to Pork at Slaughter

Antimicrobial-resistant bacteria might be transferred via the foodchain. However, that risk is rarely tracked along different production steps, e.g., from pigs at farm to meat. To close that gap, we performed a prospective study in four conventional and two organic farms from the moment pigs entered the farm until meat sampling at slaughter. Antimicrobial use was recorded (0 to 11 agents). Antimicrobial susceptibility (AMS) against 26 antibiotics, including critically important substances, was tested by microdilution, and tetA-tetB-sulI-sulII-strA-strB-bla-CTXM-qacEΔ1 were included in PCR-genotyping. From 244 meat samples of 122 pigs, 54 samples (22.1%) from 45 animals were positive for E. coli (n = 198). MICs above the breakpoint/ECOFF occurred for all antibiotics except meropenem. One isolate from organic farming was markedly resistant against beta-lactams including fourth-generation cefalosporines. AMS patterns differed remarkably between isolates from one piece of meat, varying from monoresistance to 16-fold multiresistance. Amplicon-typing revealed high similarity between isolates at slaughter and on farm. Prior pig lots andeven the farmer might serve as reservoirs for E. coli isolated from meat at slaughter. However, AMS phenotyping and genotyping indicate that antimicrobial resistance in E. coli is highly dynamic, impairing reliable prediction of health risks from findings along the production chain.

Transmission routes of antibiotic resistant bacteria: a systematic review

Background

Quantification of acquisition routes of antibiotic resistant bacteria (ARB) is pivotal for understanding transmission dynamics and designing cost-effective interventions. Different methods have been used to quantify the importance of transmission routes, such as relative risks, odds ratios (OR), genomic comparisons and basic reproduction numbers. We systematically reviewed reported estimates on acquisition routes’ contributions of ARB in humans, animals, water and the environment and assessed the methods used to quantify the importance of transmission routes.

Methods

PubMed and EMBASE were searched, resulting in 6054 articles published up until January 1st, 2019. Full text screening was performed on 525 articles and 277 are included.

Results

We extracted 718 estimates with S. aureus (n = 273), E. coli (n = 157) and Enterobacteriaceae (n = 99) being studied most frequently. Most estimates were derived from statistical methods (n = 560), mainly expressed as risks (n = 246) and ORs (n = 239), followed by genetic comparisons (n = 85), modelling (n = 62) and dosage of ARB ingested (n = 17). Transmission routes analysed most frequently were occupational exposure (n = 157), travelling (n = 110) and contacts with carriers (n = 83). Studies were mostly performed in the United States (n = 142), the Netherlands (n = 87) and Germany (n = 60). Comparison of methods was not possible as studies using different methods to estimate the same route were lacking. Due to study heterogeneity not all estimates by the same method could be pooled.

Conclusion

Despite an abundance of published data the relative importance of transmission routes of ARB has not been accurately quantified. Links between exposure and acquisition are often present, but the frequency of exposure is missing, which disables estimation of transmission routes’ importance. To create effective policies reducing ARB, estimates of transmission should be weighed by the frequency of exposure occurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07360-z.

Risk Factors and Prevalence of mcr-1-Positive Escherichia coli in Fecal Carriages Among Community Children in Southern Taiwan

Colistin is the last resort antimicrobial for treating multidrug-resistant gram-negative bacterial infections. The plasmid-mediated colistin resistance gene, mcr-1, crucially influences colistin’s resistance transmission. Human fecal carriages of mcr-1-positive Escherichia coli (E. coli) were detected in many regions worldwide; however, only a few studies have focused on children. Therefore, we identified the prevalence and risk factors of mcr-1-positive E. coli in fecal carriages among community children in Southern Taiwan. In this study, 510 stool samples were collected from April 2016 to August 2019 from the pediatric department at a medical center in Southern Taiwan. These samples were collected within 3 days after admission and were all screened for the presence of the mcr-1 gene. Diet habits, travel history, pet contact, and medical history were also obtained from participants to analyze the risk factors of their fecal carriages to mcr-1-positive E. coli. Antimicrobial susceptibility testing was determined using the VITEK 2 system and the broth microdilution test. Twelve mcr-1-positive E. coli. were isolated from 2.4% of the fecal samples. Through multivariate analysis, frequent chicken consumption (at least 3 times per week) had a significantly positive association with the presence of mcr-1-positive E. coli in fecal carriages (adjust odds ratio 6.60, 95% confidence interval1.58– 27.62, p = 0.033). Additionally, multidrug resistance was more common in mcr-1-positive E. coli. (75.0% vs. 39.5%, p = 0.031) than in non-mcr-1-positive Escherichia coli. Furthermore, the percentage of extraintestinal pathogenic E. coli in mcr-1-positive isolates was 83.3%. Some multi-locus sequence types in our mcr-1-positive E. coli were also similar to those isolated from food animals in the literature. The prevalence of fecal carriages of mcr-1-positive E. coli was low among community children in Southern Taiwan. Our data shows that chicken consumption with a higher frequency increases the risk of mcr-1-positive E. coli. in fecal carriages.

Antimicrobial Resistance in Enterococcus Spp. Isolated from a Beef Processing Plant and Retail Ground Beef

Antimicrobial use in food-producing animals has come under increasing scrutiny due to its potential association with antimicrobial resistance (AMR). Monitoring of AMR in indicator microorganisms such as Enterococcus spp. in meat production facilities and retail meat products can provide important information on the dynamics and prevalence of AMR in these environments. In this study, swabs or samples were obtained from various locations in a commercial beef packing operation (n = 600) and from retail ground beef (n = 60) over a 19-month period. All samples/swabs were enriched for Enterococcus spp., and suspected enterococci isolates were identified using species-specific PCR primers. Enterococcus faecalis was the most frequently isolated species, followed by Enterococcus hirae, which was found mostly on post-hide removal carcasses and in ground beef. Enterococcus faecium (n = 9) and E. faecalis (n = 120) isolates were further characterized for AMR. Twenty-one unique AMR profiles were identified, with 90% of isolates resistant to at least two antimicrobials and two that were resistant to nine antimicrobials. Tetracycline resistance was observed most often in E. faecalis (28.8%) and was likely mediated by tet(M). Genomic analysis of selected E. faecalis and E. faecium isolates revealed that many of the isolates in this study clustered with other publicly available genomes from ground beef, suggesting that these strains are well adapted to the beef processing environment.

IMPORTANCE Antimicrobial resistance (AMR) is a serious challenge facing the agricultural industry. Understanding the flow of antimicrobial-resistant bacteria through the beef fabrication process and into ground beef is an important step in identifying intervention points for reducing AMR. In this study, we used enterococci as indicator bacteria for monitoring AMR in a commercial beef packaging facility and in retail ground beef over a 19-month period. Although washing of carcasses post-hide removal reduced the isolation frequency of Enterococcus spp., a number of antimicrobial-resistant Enterococcus faecalis isolates were recovered from ground beef produced in the packaging plant. Genome analysis showed that several E. faecalis isolates were genetically similar to publicly available isolates recovered from retail ground beef in the United States.

The multifaceted lifestyle of enterococci: genetic diversity, ecology and risks for public health

Enterococci are long-standing members of the gastrointestinal tract of humans and many animals and they are also ubiquitously distributed in natural environments. Classically as harmless bacteria, two main species (namely Enterococcus faecalis and Enterococcus faecium) have become a leading cause of human infections, especially in hospital settings, with the worldwide spread of multidrug-resistant isolates, especially vancomycin-resistant enterococci. In this review, it will be summarized what is known about genetic diversity and ecology of enterococci with a focus on E. faecalis and E. faecium from human and non-human habitats and related risks for public health.

Spread of vancomycin-resistant Enterococcus faecium ST133 in the aquatic environment in Switzerland

OBJECTIVES

The global dissemination of vancomycin-resistant enterococci (VRE) has become a serious public-health concern. Although outbreaks are typically caused by nosocomial transmission, contaminated food and water may contribute to the spread of VRE. The aim of this study was to assess the presence of VRE in flowing surface water bodies in Switzerland and to characterise the isolates.

METHODS

Surface water was sampled from rivers, streams and canals throughout Switzerland and was screened for the presence of VRE. Whole-genome sequencing was used to identify antimicrobial resistance genes and the phylogenetic similarity of the obtained isolates.

RESULTS

VRE were detected in 6 (3.1%) of 191 water samples. The six VRE-containing samples were all collected near treated wastewater discharge sites. The six isolates were identified as Enterococcus faecium sequence type 133 (ST133) and harboured the vancomycin resistance-conferring vanA gene cluster on transposon Tn1546. They showed a close phylogenetic relationship to ST133 swine faecal isolates obtained during a previously reported screening in Switzerland.

CONCLUSION

Our results suggest that surface water contributes to the environmental dissemination of VRE. Repeated identification of ST133 clones in geographically distinct water sampling sites and swine faecal samples collected in slaughterhouses may indicate a local dominance of this VRE lineage in Switzerland.

Fecal Microbiota Transplantation: The Evolving Risk Landscape

Fecal microbiota transplantation (FMT) has been recommended in clinical guidelines for the treatment of recurrent Clostridioides difficile infection (CDI). However, it is considered investigational by most regulatory agencies. As the adoption of FMT has increased from a small group of CDI experts alone to more widespread use, there has been a corresponding increase in concern regarding potential risk. FMT is largely considered a safe procedure although risks described range from mild gastrointestinal symptoms to serious infection. Currently, there is variability in how "FMT" is characterized specifically regarding testing approach, which, in turn, impacts the risk profile. This has been highlighted by the rare cases of multidrug-resistant organisms, Shiga toxin-producing Escherichia and enteropathogenic E. coli, recently reported, where these organisms were not screened. These cases have prompted additional screening mandates from the US Food and Drug Administration (FDA), which has maintained its policy of enforcement discretion for the use of FMT for CDI not responding to standard therapy. Here, we examine the evolving risk landscape of FMT.

Can the use of older-generation beta-lactam antibiotics in livestock production over-select for beta-lactamases of greatest consequence for human medicine? An in vitro experimental model

Though carbapenems are not licensed for use in food animals in the U.S., carbapenem resistance among Enterobacteriaceae has been identified in farm animals and their environments. The objective of our study was to determine the extent to which older-generation β-lactam antibiotics approved for use in food animals in the U.S. might differentially select for resistance to antibiotics of critical importance to human health, such as carbapenems. Escherichia coli (E. coli) strains from humans, food animals, or the environment bearing a single β-lactamase gene (n = 20 each) for blaTEM-1, blaCMY-2, and blaCTX-M-* or else blaKPC/IMP/NDM (due to limited availability, often in combination with other bla genes), were identified, along with 20 E. coli strains lacking any known beta-lactamase genes. Baseline estimates of intrinsic bacterial fitness were derived from the population growth curves. Effects of ampicillin (32 μg/mL), ceftriaxone (4 μg/mL) and meropenem (4 μg/mL) on each strain and resistance-group also were assessed. Further, in vitro batch cultures were prepared by mixing equal concentrations of 10 representative E. coli strains (two from each resistance gene group), and each mixture was incubated at 37°C for 24 hours in non-antibiotic cation-adjusted Mueller-Hinton II (CAMH-2) broth, ampicillin + CAMH-2 broth (at 2, 4, 8, 16, and 32 μg/mL) and ceftiofur + CAMH-2 broth (at 0.5, 1, 2, 4, and 8μg/mL). Relative and absolute abundance of resistance-groups were estimated phenotypically. Line plots of the raw data were generated, and non-linear Gompertz models and multilevel mixed-effect linear regression models were fitted to the data. The observed strain growth rate distributions were significantly different across the groups. AmpC strains (i.e., blaCMY-2) had distinctly less robust (p < 0.05) growth in ceftriaxone (4 μg/mL) compared to extended-spectrum beta-lactamase (ESBL) producers harboring blaCTX-M-*variants. With increasing beta-lactam antibiotic concentrations, relative proportions of ESBLs and CREs were over-represented in the mixed bacterial communities; importantly, this was more pronounced with ceftiofur than with ampicillin. These results indicate that aminopenicillins and extended-spectrum cephalosporins would be expected to propagate carbapenemase-producing Enterobacteriaceae in food animals if and when Enterobacteriaceae from human health care settings enter the food animal environment.

Metabolome responses of Enterococcus faecium to acid shock and nitrite stress

Enterococcus faecium is gaining increasing interest due to its virulence and tolerance to a range of stresses (e.g., acid shock and nitrite stress in human stomach). The chemical taxonomy and basic structural features of cellular metabolite can provide us a deeper understanding of bacterial tolerance at molecular level. Here, we used hierarchical classification and molecular composition analysis to investigate the metabolome responses of E. faecium to acid shock and nitrite stress. Our results showed that considerable high biodegradable compounds (e.g., dipeptides) were produced by E. faecium under acid shock, while nitrite stress induced the accumulations of some low biodegradable compounds (e.g., organoheterocyclic compounds and benzenoids). Complete genome analysis and metabolic pathway profiling suggested that E. faecium produced high biodegradable metabolites responsible for the proton-translocation and biofilm formation, which increase its tolerance to acid shock. Yet, the presence of low biodegradable metabolites due to the nitrite exposure could disturb the bacterial productions of surface proteins, and thus inhibiting biofilm formation. Our approach uncovered the hidden interactions between intracellular metabolites and exogenous stress, and will improve the understanding of host-microbe interactions.

Post hatch recovery of a probiotic Enterococcus faecium strain in the yolk sac and intestinal tract of broiler chickens after in ovo injection

Concerns about antibiotic-resistant bacteria and their presence in animal products grow and thus alternatives to use of antibiotics in animal production are being investigated. Probiotics have gained increased focus due to improvements in performance, immune health and pathogen reduction when provided to poultry through feed. These traits may be further improved if probiotics can be provided to the embryo before hatch, before meeting environmental pathogens. The objective was to determine the faith of a probiotic Enterococcus faecium (M74) strain in the yolk sac and intestinal tract of broiler chickens after injection into hatching eggs. E. faecium M74 (1.4 × 107 CFU/egg) was applied in ovo at day 18 of incubation. From 1- and 7-day-old chickens, 20 samples from yolk sac, caecal tonsils and rest of the intestinal tract were subjected to CFU counting. Isolates from a sample subset were typed by pulsed-field gel electrophoresis (PFGE). Enterococci were found in varying numbers: 1.0 × 104-2.2 × 1010 CFU/g. The prevalence of M74 PFGE profiles was high in 1-day-old (88%) and 7-day-old chickens (67%). This demonstrates that the embryos ingested M74 before hatching, that M74 is viable for intestinal colonization through in ovo administration, and that the strain multiplies in the chickens gastrointestinal tract post hatching.

Surveillance of Enterococcus spp. reveals distinct species and antimicrobial resistance diversity across a One-Health continuum

For a One-Health investigation of antimicrobial resistance (AMR) in Enterococcus spp., isolates from humans and beef cattle along with abattoirs, manured fields, natural streams, and wastewater from both urban and cattle feedlot sources were collected over two years. Species identification of Enterococcus revealed distinct associations across the continuum. Of the 8430 isolates collected, Enterococcus faecium and Enterococcus faecalis were the main species in urban wastewater (90%) and clinical human isolates (99%); Enterococcus hirae predominated in cattle (92%) and feedlot catch-basins (60%), whereas natural streams harbored environmental Enterococcus spp. Whole-genome sequencing of E. faecalis (n = 366 isolates) and E. faecium (n = 342 isolates), revealed source clustering of isolates, indicative of distinct adaptation to their respective environments. Phenotypic resistance to tetracyclines and macrolides encoded by tet(M) and erm(B) respectively, was prevalent among Enterococcus spp. regardless of source. For E. faecium from cattle, resistance to β-lactams and quinolones was observed among 3% and 8% of isolates respectively, compared to 76% and 70% of human clinical isolates. Clinical vancomycin-resistant E. faecium exhibited high rates of multi-drug resistance, with resistance to all β-lactam, macrolides, and quinolones tested. Differences in the AMR profiles among isolates reflected antimicrobial use practices in each sector of the One-Health continuum.

Significant reduction of vancomycin resistant E. faecium in the Norwegian broiler population coincided with measures taken by the broiler industry to reduce antimicrobial resistant bacteria

Vancomycin resistant enterococci (VRE) belong to the most common causes of nosocomial infections worldwide. It has been reported that use of the glycopeptide growth promoter avoparcin selected for a significant livestock-reservoir of VRE in many European countries, including Norway. However, although avoparcin was banned as a feed-additive in 1995, VRE have for unknown reasons consistently been reported in samples from Norwegian broilers. When avoparcin was banned, broiler-feed was supplemented with the polyether ionophore narasin in order to control the diseases coccidiosis and the frequent sequela necrotic enteritis. A potential link between transferrable vancomycin resistance and reduced susceptibility to narasin was recently reported. The use of narasin as a feed additive was abolished by the Norwegian broiler industry in 2016 and since then, broilers have been reared without in-feed antibacterial supplements. In this study, we demonstrate that all VRE isolates from Norwegian broilers collected in 2006–2014 displayed reduced susceptibility to narasin. Surveillance data collected two years after the narasin abolishment show a significant reduction in VRE, below the detection limit of the surveillance method, and a concurrent marked reduction in Enterococcus faecium with reduced susceptibility to narasin. The significant decline of E. faecium with reduced susceptibility to these antimicrobial compounds also coincided with an increased focus on cleaning and disinfection between broiler flocks. Furthermore, data from a controlled in vivo experiment using Ross 308 broilers indicate that the proportion of E. faecium with reduced susceptibility to narasin was heavily reduced in broilers fed a narasin-free diet compared to a diet supplemented with narasin. Our results are consistent with that the abolishment of this feed additive, possibly in combination with the increased focus on cleaning and disinfection, has had a substantial impact on the occurrence of VRE in the Norwegian broiler population.

Fate of antibiotics and antibiotic resistance genes in a full-scale restaurant food waste treatment plant: Implications of the roles beyond heavy metals and mobile genetic elements

Is our food safe and free of the crisis of antibiotics and antibiotic resistance (AR)? And will the derived food waste (FW) impose AR risk to the environment after biological treatment? This study used restaurant FW leachates flowing through a 200 tons-waste/day biological treatment plant as a window to investigate the fate of antibiotics and antibiotic-resistance genes (ARGs) during the acceptance and treatment of FW. Sulfonamides (sulfamethazine, sulfamethoxazole) and quinolones (ciprofloxacin, enrofloxacin, ofloxacin) were detected during FW treatment, while tetracyclines, macrolides and chloramphenicols were not observable. ARGs encoding resistance to sulfonamides, tetracyclines and macrolides emerged in FW leachates. Material flow analysis illustrated that the total amount of antibiotics (except sulfamethazine) and ARGs were constant during FW treatment processes. Both the concentration and total amount of most antibiotics and ARGs fluctuated during treatment, physical processes (screening, centrifugation, solid-liquid and oil-water separation) did not decrease antibiotic or ARGs concentrations or total levels permanently; the affiliated wastewater treatment plant appeared to remove sulfonamides and most ARGs concentrations and total amount. Heavy metals Ni, Co and Cu were important for disseminating antibiotics concentrations and MGEs for distributing ARGs concentrations. Humic substances (fulvic acids, hydrophilic fractions), C-associated and N-associated contents were essential for the distribution of the total amounts of antibiotics and ARGs. Overall, this study implied that human food might not be free of antibiotics and ARGs, and FW was an underestimated AR pool with various determinants. Nonetheless, derived hazards of FW could be mitigated through biological treatment with well-planned daily operations.

Antimicrobial Resistance in Enterococcus spp. of animal origin

Enterococci are natural inhabitants of the intestinal tract in humans and many animals, including food-producing and companion animals. They can easily contaminate the food and the environment, entering the food chain. Moreover, Enterococcus is an important opportunistic pathogen, especially the species E. faecalis and E. faecium, causing a wide variety of infections. This microorganism not only contains intrinsic resistance mechanisms to several antimicrobial agents, but also has the capacity to acquire new mechanisms of antimicrobial resistance. In this review we analyze the diversity of enterococcal species and their distribution in the intestinal tract of animals. Moreover, resistance mechanisms for different classes of antimicrobials of clinical relevance are reviewed, as well as the epidemiology of multidrug-resistant enterococci of animal origin, with special attention given to beta-lactams, glycopeptides, and linezolid. The emergence of new antimicrobial resistance genes in enterococci of animal origin, such as optrA and cfr, is highlighted. The molecular epidemiology and the population structure of E. faecalis and E. faecium isolates in farm and companion animals is presented. Moreover, the types of plasmids that carry the antimicrobial resistance genes in enterococci of animal origin are reviewed.

Antimicrobial resistance: A global emerging threat to public health systems

Antimicrobial resistance (AMR) became in the last two decades a global threat to public health systems in the world. Since the antibiotic era, with the discovery of the first antibiotics that provided consistent health benefits to human medicine, the misuse and abuse of antimicrobials in veterinary and human medicine have accelerated the growing worldwide phenomenon of AMR. This article presents an extensive overview of the epidemiology of AMR, with a focus on the link between food producing-animals and humans and on the legal framework and policies currently implemented at the EU level and globally. The ways of responding to the AMR challenges foresee an array of measures that include: designing more effective preventive measures at farm level to reduce the use of antimicrobials; development of novel antimicrobials; strengthening of AMR surveillance system in animal and human populations; better knowledge of the ecology of resistant bacteria and resistant genes; increased awareness of stakeholders on the prudent use of antibiotics in animal productions and clinical arena; and the public health and environmental consequences of AMR. Based on the global nature of AMR and considering that bacterial resistance does not recognize barriers and can spread to people and the environment, the article ends with specific recommendations structured around a holistic approach and targeted to different stakeholders.

Prevalence and Antimicrobial Resistance of Enterococci Isolated from Retail Meats in the United States, 2002 to 2014

Bacteria of the genus Enterococcus are important human pathogens that are frequently resistant to a number of clinically important antibiotics. They are also used as markers of animal fecal contamination of human foods and are employed as sentinel organisms for tracking trends in resistance to antimicrobials with Gram-positive activity. As part of the National Antimicrobial Resistance Monitoring System (NARMS), we evaluated several retail meat commodities for the presence of enterococci from 2002 to 2014, and we found 92.0% to be contaminated. The majority of isolates were either Enterococcus faecalis (64.0%) or Enterococcus faecium (28.6%), and the antimicrobial resistance of each isolate was assessed by broth microdilution. The resistance prevalences for several drugs, including erythromycin and gentamicin, were significantly higher among poultry isolates, compared to retail beef or pork isolates. None of the isolates was resistant to the clinically important human drug vancomycin, only 1 isolate was resistant to linezolid, and resistance to tigecycline was below 1%. In contrast, a majority of both E. faecalis (67.5%) and E. faecium (53.7%) isolates were resistant to tetracycline. Overall, the robust NARMS testing system employed consistent sampling practices and methods throughout the testing period, with the only significant trend in resistance prevalence being decreased E. faecium resistance to penicillin. These data provide excellent baseline levels of resistance that can be used to measure future changes in resistance prevalence that may result from alterations in the use of antimicrobials in food animal production.IMPORTANCE Enterococci, including E. faecalis and E. faecium, are present in the guts of food-producing animals and are used as a measure of fecal contamination of meat. We used the large consistent sampling methods of NARMS to assess the prevalence of Enterococcus strains isolated from retail meats, and we found over 90% of meats to be contaminated with enterococci. We also assessed the resistance of the Enterococcus strains, commonly used as a measure of resistance to agents with Gram-positive activity, in foods. Resistance prevalence was over 25% for some antimicrobials and sample sources but was less than 1% for several of the most important therapeutic agents used in human medicine.

Vancomycin-Resistant Enterococci: A Review of Antimicrobial Resistance Mechanisms and Perspectives of Human and Animal Health

Vancomycin-resistant enterococci (VRE) are both of medical and public health importance associated with serious multidrug-resistant infections and persistent colonization. Enterococci are opportunistic environmental inhabitants with a remarkable adaptive capacity to evolve and transmit antimicrobial-resistant determinants. The VRE gene operons show distinct genetic variability and apparently continued evolution leading to a variety of antimicrobial resistance phenotypes and various environmental and livestock reservoirs for the most common van genes. Such complex diversity renders a number of important therapeutic options including "last resort antibiotics" ineffective and poses a particular challenge for clinical management. Enterococci resistance to glycopeptides and multidrug resistance warrants attention and continuous monitoring.

The Risk of Some Veterinary Antimicrobial Agents on Public Health Associated with Antimicrobial Resistance and their Molecular Basis

The risk of antimicrobial agents used in food-producing animals on public health associated with antimicrobial resistance continues to be a current topic of discussion as related to animal and human public health. In the present review, resistance monitoring data, and risk assessment results of some important antimicrobial agents were cited to elucidate the possible association of antimicrobial use in food animals and antimicrobial resistance in humans. From the selected examples, it was apparent from reviewing the published scientific literature that the ban on use of some antimicrobial agents (e.g., avoparcin, fluoroquinolone, tetracyclines) did not change drug resistance patterns and did not mitigate the intended goal of minimizing antimicrobial resistance. The use of some antimicrobial agents (e.g., virginiamycin, macrolides, and cephalosporins) in food animals may have an impact on the antimicrobial resistance in humans, but it was largely depended on the pattern of drug usage in different geographical regions. The epidemiological characteristics of resistant bacteria were closely related to molecular mechanisms involved in the development, fitness, and transmission of antimicrobial resistance.

The risk of low concentrations of antibiotics in agriculture for resistance in human health care

The contribution of antibiotic resistance originally selected for in the agricultural sector to resistance in human pathogens is not known exactly, but is unlikely to be negligible. It is estimated that 50% to 80% of all antibiotics used are applied in agriculture and the remainder for treating infections in humans. Since dosing regimens are less controlled in agriculture than in human health care, veterinary and environmental microbes are often exposed to sublethal levels of antibiotics. Exposure to sublethal drug concentrations must be considered a risk factor for de novo resistance, transfer of antimicrobial resistant (AMR) genes, and selection for already existing resistance. Resistant zoonotic agents and commensal strains carrying AMR genes reach the human population by a variety of routes, foodstuffs being only one of these. Based on the present knowledge, short treatments with the highest dose that does not cause unacceptable side-effects may be optimal for achieving therapeutic goals while minimizing development of resistance. Novel approaches such as combination or alternating therapy are promising, but need to be explored further before they can be implemented in daily practice.

Human health risks associated with antimicrobial-resistant enterococci and Staphylococcus aureus on poultry meat

Enterococci and staphylococci are frequent contaminants on poultry meat. Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus are also well-known aetiological agents of a wide variety of infections resulting in major healthcare costs. This review provides an overview of the human health risks associated with the occurrence of these opportunistic human pathogens on poultry meat with particular focus on the risk of food-borne transmission of antimicrobial resistance. In the absence of conclusive evidence of transmission, this risk was inferred using data from scientific articles and national reports on prevalence, bacterial load, antimicrobial resistance and clonal distribution of these three species on poultry meat. The risks associated with ingestion of antimicrobial-resistant enterococci of poultry origin comprise horizontal transfer of resistance genes and transmission of multidrug-resistant E. faecalis lineages such as sequence type ST16. Enterococcus faecium lineages occurring in poultry meat products are distantly related to those causing hospital-acquired infections but may act as donors of quinupristin/dalfopristin resistance and other resistance determinants of clinical interest to the human gut microbiota. Ingestion of poultry meat contaminated with S. aureus may lead to food poisoning. However, antimicrobial resistance in the toxin-producing strains does not have clinical implications because food poisoning is not managed by antimicrobial therapy. Recently methicillin-resistant S. aureus of livestock origin has been reported on poultry meat. In theory handling or ingestion of contaminated meat is a potential risk factor for colonization by methicillin-resistant S. aureus. However, this risk is presently regarded as negligible by public health authorities.

Horizontal transfer of antibiotic resistance from Enterococcus faecium of fermented meat origin to clinical isolates of E. faecium and Enterococcus faecalis

Enterococcus species are part of the normal intestinal flora of a large number of mammals including humans and consequently, they can be used as indicators of faecal contamination in food and water for human consumption. Their presence in large numbers in foods may indicate a lapse in sanitation and their ability to serve as a genetic reservoir of transferable antibiotic resistance is of concern. In the present study, Enterococcus spp., isolated from commercially fermented meat and human clinical specimen were studied to determine genetic relationships. SmaI pulsed-field gel electrophoresis (PFGE) patterns exhibited genomic heterogeneity within and between both groups of isolates. However, in spite of this heterogeneity there were still substantial phenotypic similarities which suggested that food might be a potential vehicle for distribution of resistant bacteria among humans. In vitro conjugation experiments demonstrated transfer of the tetracycline resistant determinant, tet(M), from Enterococcus faecium S27 isolated from fermented sausage to clinical isolates of both E. faecium and Enterococcus faecalis. The streptomycin resistance of E. faecium S27 was also transferred to a clinical strain, E. faecalis 82916, which was confirmed by the presence of the streptomycin resistance gene, aadA, in the donor and transconjugant strains. Since the aadA gene is associated with a class 1 integron, results also suggested that resistance transfer might have occurred via an integron. It appears this is the first identification of a class 1 integron in E. faecium isolated from food. The importance of food enterococci as a reservoir of antibiotic resistance genes and the potential for their genetic transfer to human strains following consumption of uncooked or undercooked contaminated meat is underlined by this work.

Mechanisms of β-lactam antimicrobial resistance and epidemiology of major community- and healthcare-associated multidrug-resistant bacteria

Alexander Fleming's discovery of penicillin heralded an age of antibiotic development and healthcare advances that are premised on the ability to prevent and treat bacterial infections both safely and effectively. The resultant evolution of antimicrobial resistant mechanisms and spread of bacteria bearing these genetic determinants of resistance are acknowledged to be one of the major public health challenges globally, and threatens to unravel the gains of the past decades. We describe the major mechanisms of resistance to β-lactam antibiotics - the most widely used and effective antibiotics currently - in both Gram-positive and Gram-negative bacteria, and also briefly detail the existing and emergent pharmacological strategies to overcome such resistance. The global epidemiology of the four major types of bacteria that are responsible for the bulk of antimicrobial-resistant infections in the healthcare setting - methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Enterobactericeae, and Acinetobacter baumannii - are also briefly described.

Mini-review: Epidemiology and zoonotic potential of multiresistant bacteria and Clostridium difficile in livestock and food

AIM

Information on the epidemiology of multiresistant bacteria (MRB) with zoonotic potential is growing but still remains quite incomplete. This narrative mini-review provides a general overview of the epidemiology of the most important zoonotic MRB in cattle, swine and poultry in Europe.

METHODS

A literature search was conducted mainly on the PubMed website including articles published until April 2012.

RESULTS

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) especially poses a zoonotic risk to people working in close contact with livestock. These people may become carriers themselves and the hazard of transmission into health-care facilities needs surveillance. Extended-spectrum beta-lactamases (ESBL) producing bacteria are widely spread in both humans and livestock, sharing similar genotypes, especially of the CTX-M-group, which makes a zoonotic transfer very likely. Identical strains of vancomycin-resistant enterococci (VRE) were found both in humans and animals, after ingestion of animal strains transient colonization of the human gut may be possible. Only a few data are available on the transmission of methicillin-resistant coagulase-negative staphylococci (MR-CoNS) between humans and animals. Direct contact to colonized animals may be a risk factor as well as the exchange of resistance genes between human and animal staphylococci. Clostridium difficile (C. difficile) ribotype 078 emerges in livestock and humans and a zoonotic transmission seems probable as genotypes and diseases resemble each other.

CONCLUSION

All discussed MRB and C. difficile are important nosocomial agents which also occur in livestock and were found in foods of animal origin. Further analysis is needed to reveal the exact transmission routes and to perform a reliable risk assessment.

Quantitative risk analysis for potentially resistant E. coli in surface waters caused by antibiotic use in agricultural systems

Antibiotics are frequently used in agricultural systems to promote livestock health and to control bacterial contaminants. Given the upsurge of the resistant fecal indicator bacteria (FIB) in the surface waters, a novel statistical method namely, microbial risk assessment (MRA) was performed, to evaluate the probability of infection by resistant FIB on populations exposed to recreational waters. Diarrheagenic Escherichia coli, except E. coli O157:H7, were selected for their prevalence in aquatic ecosystem. A comparative study between a typical E. coli pathway and a case scenario aggravated by antibiotic use has been performed via Crystal Ball® software in an effort to analyze a set of available inputs provided by the US institutions including E. coli concentrations in US Great Lakes through using random sampling and probability distributions. Results from forecasting a possible worst-case scenario dose-response, accounted for an approximate 50% chance for 20% of the exposed human populations to be infected by recreational water in the U.S. However, in a typical scenario, there is a 50% chance of infection for only 1% of the exposed human populations. The uncertain variable, E. coli concentration accounted for approximately 92.1% in a typical scenario as the major contributing factor of the dose-response model. Resistant FIB in recreational waters that are exacerbated by a low dose of antibiotic pollutants would increase the adverse health effects in exposed human populations by 10 fold.

Antimicrobial resistance: action to combat the rising microbial challenges

Antimicrobial therapy transformed medical practice from a merely diagnosis-focused approach 80 years ago to a treatment-focused approach, saving millions of lives in the years to follow. Today, numerous medical advances made possible by effective antibiotics are being threatened by the relentlessly rising rates of bacteria resistant to all currently available antibiotics. This phenomenon is a consequence of antibiotic misuse, which exerts undue selective pressure on micro-organisms, combined with defective infection control practices that accelerate their spread. Its impact on societies worldwide is immense, resulting in loss of human life and money. An alarming pattern of resistance involving multidrug-resistant and sometimes pandrug-resistant Gram-negative bacteria is currently emerging. In response to the global public health threat posed by antimicrobial resistance (AMR), a number of national and international actions and initiatives have been developed in recent years to address this issue. Although the optimally effective and cost-effective strategy to reduce AMR is not known, a multifaceted approach is most likely to be successful. It should include actions aiming at optimising antibiotic use, strengthening surveillance and infection control, and improving healthcare worker and public education with regard to antibiotics. Research efforts to bring new effective antibiotics to patients need to be fostered in order to negate the consequences of the current lack of antimicrobial therapy options. A holistic view of AMR as well as intersectoral collaboration between human and veterinary medicine is required to best address the problem.

Antibiotic-resistant Enterococcus faecalis in abattoir pigs and plasmid colocalization and cotransfer of tet(M) and erm(B) genes

This study was conducted to determine plasmid colocalization and transferability of both erm(B) and tet(M) genes in Enterococcus faecalis isolates from abattoir pigs in Canada. A total of 124 E. faecalis isolates from cecal contents of abattoir pigs were examined for antibiotic susceptibility. High percentages of resistance to macrolides and tetracyclines were found. Two predominant multiresistance patterns of E. faecalis were examined by PCR and sequencing for the presence of genes encoding antibiotic resistance. Various combinations of antibiotic resistance genes were detected; erm(B) and tet(M) were the most common genes. Plasmid profiling and hybridization revealed that both genes were colocated on a ~9-kb transferable plasmid in six strains with the two predominant multiresistant patterns. Plasmid colocalization and cotransfer of tet(M) and erm(B) genes in porcine E. faecalis isolates indicates that antibiotic coselection and transferability could occur via this single genetic element. To our knowledge, this is the first report on plasmid colocalization and transferability of erm(B) and tet(M) genes in E. faecalis on a mobile genetic element of ~9 kb. Physical linkage between important antibiotic resistance determinants in enterococci is of interest for predicting potential transfer to other bacterial genera.

Enterococcus faecalis of human and poultry origin share virulence genes supporting the zoonotic potential of E. faecalis

Enterococcus faecalis is a major cause of nosocomial infections in humans and has been linked to severe extra-intestinal infections in poultry. A zoonotic potential has been suggested and the aim of the present study was to investigate similarities in virulence gene profiles of E. faecalis originating from infections in humans and poultry respectively. A total of 106 isolates of E. faecalis [26 human clinical isolates, 60 poultry clinical isolates (including two small-colony variants (SCVs) and 20 poultry cloacal isolates] were investigated for presence of seven virulence-associated genes: ace, asa1, cylA, efaA, EF0591, esp and gelE. For each gene, the PCR-amplification product was sequenced from one isolate in each group to explore intragenic variations between genes of human and poultry origin. Haemolytic and protease activities were assessed and isolates were assigned a sequence type (ST). Three of the seven genes investigated (ace, efaA and gelE) were present in all isolates. The asa1 was detected in 63/80 and 13/26 isolates of poultry and human origin respectively. For cylA, the numbers were 46/80 and 14/26 respectively. Among poultry isolates, esp and EF0591 were the least frequently observed genes (1/80 and 20/80 respectively); the prevalences among human isolates were 1/26 and 18/26 respectively. A high degree of similarity between genes in human and poultry isolates were confirmed by sequencing of amplification products. None of the cylA-positive isolates demonstrated haemolytic activity, while the phenotypic expression of gelatinase varied. The ST16 was the only ST shared by human and poultry isolates. The SCV isolates did not show a unique virulence profile or phylogeny. In conclusion, regardless of the distinct phylogenetic background of most E. faecalis isolates of human and poultry origin, we found major similarities in virulence gene profile and gene sequences in isolates from the two sources, supporting the zoonotic risk associated with this organism.

Food animals and antimicrobials: impacts on human health

Antimicrobials are valuable therapeutics whose efficacy is seriously compromised by the emergence and spread of antimicrobial resistance. The provision of antibiotics to food animals encompasses a wide variety of nontherapeutic purposes that include growth promotion. The concern over resistance emergence and spread to people by nontherapeutic use of antimicrobials has led to conflicted practices and opinions. Considerable evidence supported the removal of nontherapeutic antimicrobials (NTAs) in Europe, based on the "precautionary principle." Still, concrete scientific evidence of the favorable versus unfavorable consequences of NTAs is not clear to all stakeholders. Substantial data show elevated antibiotic resistance in bacteria associated with animals fed NTAs and their food products. This resistance spreads to other animals and humans-directly by contact and indirectly via the food chain, water, air, and manured and sludge-fertilized soils. Modern genetic techniques are making advances in deciphering the ecological impact of NTAs, but modeling efforts are thwarted by deficits in key knowledge of microbial and antibiotic loads at each stage of the transmission chain. Still, the substantial and expanding volume of evidence reporting animal-to-human spread of resistant bacteria, including that arising from use of NTAs, supports eliminating NTA use in order to reduce the growing environmental load of resistance genes.

Antimicrobial-resistant enterococci in animals and meat: a human health hazard?

Enterococcus faecium and Enterococcus faecalis belong to the gastrointestinal flora of humans and animals. Although normally regarded harmless commensals, enterococci may cause a range of different infections in humans, including urinary tract infections, sepsis, and endocarditis. The use of avoparcin, gentamicin, and virginiamycin for growth promotion and therapy in food animals has lead to the emergence of vancomycin- and gentamicin-resistant enterococci and quinupristin/dalfopristin-resistant E. faecium in animals and meat. This implies a potential risk for transfer of resistance genes or resistant bacteria from food animals to humans. The genes encoding resistance to vancomycin, gentamicin, and quinupristin/dalfopristin have been found in E. faecium of human and animal origin; meanwhile, certain clones of E. faecium are found more frequently in samples from human patients, while other clones predominate in certain animal species. This may suggest that antimicrobial-resistant E. faecium from animals could be regarded less hazardous to humans; however, due to their excellent ability to acquire and transfer resistance genes, E. faecium of animal origin may act as donors of antimicrobial resistance genes for other more virulent enterococci. For E. faecalis, the situation appears different, as similar clones of, for example, vancomycin- and gentamicin-resistant E. faecalis have been obtained from animals and from human patients. Continuous surveillance of antimicrobial resistance in enterococci from humans and animals is essential to follow trends and detect emerging resistance.

Erythromycin- and tetracycline-resistant lactobacilli in Italian fermented dry sausages

AIMS

To assess the frequency of erythromycin- and tetracycline-resistant lactobacilli in Italian fermented dry sausages.

METHODS AND RESULTS

We isolated lactobacilli colonies from 20 salami from the north of Italy (Piacenza province) using selective medium supplemented with erythromycin or tetracycline; we determined the minimum inhibitory concentration and searched for selected erythromycin and tetracycline resistance genes. A total of 312 lactobacilli colonies were genetically ascribed to 60 different strains belonging to seven Lactobacillus species. Lactobacillus sakei, Lactobacillus curvatus and Lactobacillus plantarum were the most frequently found species. Thirty strains (50%) were phenotypically resistant to erythromycin, 45 (75%) to tetracycline and 27 (45%) were resistant to both. The most frequently detected resistance genes were tet(M) and erm(B).

CONCLUSIONS

This study provides evidence of the presence of tetracycline- and, to a lesser extent, erythromycin-resistant lactobacilli in fermented dry sausages produced in northern Italy.

SIGNIFICANCE AND IMPACT OF THE STUDY

Although these antibiotic-resistant lactobacilli could serve as reservoir organisms, in our study, 16 of 20 salami could be considered safe in regard to possible antibiotic resistance gene transfer to pathogens, whereas 4 of 20 could represent a borderline situation.

The impact of different antibiotic regimens on the emergence of antimicrobial-resistant bacteria

Backgroud

The emergence and ongoing spread of antimicrobial-resistant bacteria is a major public health threat. Infections caused by antimicrobial-resistant bacteria are associated with substantially higher rates of morbidity and mortality compared to infections caused by antimicrobial-susceptible bacteria. The emergence and spread of these bacteria is complex and requires incorporating numerous interrelated factors which clinical studies cannot adequately address.

Methods/Principal Findings

A model is created which incorporates several key factors contributing to the emergence and spread of resistant bacteria including the effects of the immune system, acquisition of resistance genes and antimicrobial exposure. The model identifies key strategies which would limit the emergence of antimicrobial-resistant bacterial strains. Specifically, the simulations show that early initiation of antimicrobial therapy and combination therapy with two antibiotics prevents the emergence of resistant bacteria, whereas shorter courses of therapy and sequential administration of antibiotics promote the emergence of resistant strains.

Conclusions/Significance

The principal findings suggest that (i) shorter lengths of antibiotic therapy and early interruption of antibiotic therapy provide an advantage for the resistant strains, (ii) combination therapy with two antibiotics prevents the emergence of resistance strains in contrast to sequential antibiotic therapy, and (iii) early initiation of antibiotics is among the most important factors preventing the emergence of resistant strains. These findings provide new insights into strategies aimed at optimizing the administration of antimicrobials for the treatment of infections and the prevention of the emergence of antimicrobial resistance.

Vancomycin-resistant Enterococcus – A Review From a Singapore Perspective

Introduction: Vancomycin-resistant enterococcus (VRE) can cause serious infections in vulnerable, immunocompromised patients. Materials and Methods: In this article, we summarise current data on epidemiology, detection, treatment and prevention of VRE. Results: VRE was first isolated in Singapore in 1994 and until 2004 was only sporadically encountered in our public hospitals. After 2 outbreaks in 2004 and in 2005, VRE has become established in our healthcare institutions. Multiple studies have shown that VRE spreads mainly via contaminated hands, cloths and portable equipment carried by healthcare workers. Conclusions: Only a comprehensive programme (consisting of active surveillance, isolation of colonised/infected patients, strict adherence to proper infection control practices and anti-microbial stewardship) can limit the spread of these organisms. In addition to monitoring the compliance with traditional infection control measures, new strategies that merit consideration include pre-emptive isolation of patients in high-risk units and molecular techniques for the detection of VRE. Keywords: Antibiotic resistance, Infection control, Outbreaks, Surveillance

Use of Antimicrobial Agents in Veterinary Medicine and Implications for Human Health

This review discusses why veterinary usage of antimicrobial agents is wrongly accused of causing a substantial part of the problem of resistant human pathogens. Without doubt, resistant organisms in animals are selected by veterinary antimicrobials. However, these are not a major human health risk either because the role of veterinary usage in selection or propagation is insignificant, or because resistant populations selected by veterinary usage do not pose a substantial risk to human health. Indeed, resistant bacterial infections in humans causing serious quantitative and qualitative health consequences are rarely food-borne and are not the same as those selected by veterinary usage of antimicrobial agents. The available evidence for veterinary selection of resistance, transmission to humans, and subsequent health consequences are reviewed for food-borne zoonotic pathogens. A risk assessment strategy is proposed to quantify potential hazards in order to decide on the most effective risk management strategy.

Meta-analysis of experimental data concerning antimicrobial resistance gene transfer rates during conjugation

This paper presents the results of a meta-analysis of published transfer rates of antimicrobial resistance genes. A total of 34 papers were identified, of which 28 contained rates estimated in relation to either donor or recipient bacterial counts. The published rates ranged from 10(-2) to 10(-9). Generalized linear modeling was conducted to identify the factors influencing this variation. Highly significant associations between transfer frequency and both the donor (P = 1.2 x 10(-4)) and recipient (P = 1.0 x 10(-5)) genera were found. Also significant was whether the donor and recipient strains were of the same genus (P = 0.023) and the nature of the genetic element (P = 0.0019). The type of experiment, in vivo or in vitro, approached statistical significance (P = 0.12). Parameter estimates from a general linear model were used to estimate the probability of transfer of antimicrobial resistance genes to potential pathogens in the intestine following oral ingestion. The mean logarithms of these probabilities are in the range of [-7.0, -3.1]. These probability distributions are suitable for use in the quantitative assessment of the risk of transfer of antimicrobial resistance genes to the intestinal flora of humans and animals.

Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part I)

Through the use of the new tools of genetic engineering, genes can be introduced into the same plant or animal species or into plants or animals that are not sexually compatible-the latter is a distinction with classical breeding. This technology has led to the commercial production of genetically engineered (GE) crops on approximately 250 million acres worldwide. These crops generally are herbicide and pest tolerant, but other GE crops in the pipeline focus on other traits. For some farmers and consumers, planting and eating foods from these crops are acceptable; for others they raise issues related to safety of the foods and the environment. In Part I of this review some general and food issues raised regarding GE crops and foods will be addressed. Responses to these issues, where possible, cite peer-reviewed scientific literature. In Part II to appear in 2009, issues related to environmental and socioeconomic aspects of GE crops and foods will be covered.

Modeling antibiotic resistance in hospitals: the impact of minimizing treatment duration

Infections caused by antibiotic-resistant pathogens are a global public health problem. Numerous individual- and population-level factors contribute to the emergence and spread of these pathogens. An individual-based model (IBM), formulated as a system of stochastically determined events, was developed to describe the complexities of the transmission dynamics of antibiotic-resistant bacteria. To simplify the interpretation and application of the model's conclusions, a corresponding deterministic model was created, which describes the average behavior of the IBM over a large number of simulations. The integration of these two model systems provides a quantitative analysis of the emergence and spread of antibiotic-resistant bacteria, and demonstrates that early initiation of treatment and minimization of its duration mitigates antibiotic resistance epidemics in hospitals.

Effect of cheese consumption on emergence of antimicrobial resistance in the intestinal microflora induced by a short course of amoxicillin-clavulanic acid

AIM

To study in a sequential prospective trial, the effect of cheese consumption on the emergence of Escherichia coli and enterococci resistance to amoxicillin after amoxicillin-clavulanic acid (amoxiclav) treatment.

METHODS AND RESULTS

The study comprised two phases separated by 1 year. Each phase lasted 75 days for each volunteer (from day -13 to day 61). During the first phase, 18 healthy volunteers were given a 1-g dose of amoxiclav orally twice a day for 5 days (from day 0 to day 4). The design of phase 2 was identical to that of phase 1, except that the volunteers consumed 100 g of hard-cooked cheese from day -6 to day 19. Faecal samples were collected 20 times throughout the trial and were quantitatively assayed for total and amoxicillin-resistant (Amox(R)) E. coli and enterococci. The consumption of experimental cheese was associated with a decrease of Amox(R) enterococci during the post-antibiotic period, with the maximum level of Amox(R) enterococci falling from 6.2% to 0.03%. This effect was not observed for E. coli, and the type of cheese (raw milk vs pasteurized milk) did not influence the results.

CONCLUSIONS

Consumption of cheese during amoxiclav treatment reduces the emergence of Amox(R) enterococci in faeces. SIGNIFICANCE AND CLINICAL IMPACT OF THE STUDY: Our clinical pilot trial suggests that there are likely to be benefits from consuming probiotic-containing cheese during antibiotic treatment.

Influx of enterococci and associated antibiotic resistance and virulence genes from ready-to-eat food to the human digestive tract

The influx of enterococcal antibiotic resistance (AR) and virulence genes from ready-to-eat food (RTEF) to the human digestive tract was assessed. Three RTEFs (chicken salad, chicken burger, and carrot cake) were sampled from five fast-food restaurants five times in summer (SU) and winter (WI). The prevalence of enterococci was significantly higher in SU (92.0% of salad samples and 64.0% of burger samples) than in WI (64.0% of salad samples and 24.0% of burger samples). The overall concentrations of enterococci during the two seasons were similar ( approximately 10(3) CFU/g); the most prevalent were Enterococcus casseliflavus (41.5% of isolates) and Enterococcus hirae (41.5%) in WI and Enterococcus faecium (36.8%), E. casseliflavus (27.6%), and Enterococcus faecalis (22.4%) in SU. Resistance in WI was detected primarily to tetracycline (50.8%), ciprofloxacin (13.8%), and erythromycin (4.6%). SU isolates were resistant mainly to tetracycline (22.8%), erythromycin (22.1%), and kanamycin (13.0%). The most common tet gene was tet(M) (35.4% of WI isolates and 11.9% of SU isolates). The prevalence of virulence genes (gelE, asa1, cylA, and esp) and marker genes for clinical isolates (EF_0573, EF_0592, EF_0605, EF_1420, EF_2144, and pathogenicity island EF_0050) was low (< or =12.3%). Genotyping of E. faecalis and E. faecium using pulsed-field gel electrophoresis revealed that the food contamination likely originated from various sources and that it was not clonal. Our conservative estimate (single AR gene copy per cell) for the influx of tet genes alone to the human digestive tract is 3.8 x 10(5) per meal (chicken salad). This AR gene influx is frequent because RTEFs are commonly consumed and that may play a role in the acquisition of AR determinants in the human digestive tract.

What do we feed to food-production animals? A review of animal feed ingredients and their potential impacts on human health

OBJECTIVE

Animal feeding practices in the United States have changed considerably over the past century. As large-scale, concentrated production methods have become the predominant model for animal husbandry, animal feeds have been modified to include ingredients ranging from rendered animals and animal waste to antibiotics and organoarsenicals. In this article we review current U.S. animal feeding practices and etiologic agents that have been detected in animal feed. Evidence that current feeding practices may lead to adverse human health impacts is also evaluated.

DATA SOURCES

We reviewed published veterinary and human-health literature regarding animal feeding practices, etiologic agents present in feed, and human health effects along with proceedings from animal feed workshops.

DATA EXTRACTION

Data were extracted from peer-reviewed articles and books identified using PubMed, Agricola, U.S. Department of Agriculture, Food and Drug Administration, and Centers for Disease Control and Prevention databases.

DATA SYNTHESIS

Findings emphasize that current animal feeding practices can result in the presence of bacteria, antibiotic-resistant bacteria, prions, arsenicals, and dioxins in feed and animal-based food products. Despite a range of potential human health impacts that could ensue, there are significant data gaps that prevent comprehensive assessments of human health risks associated with animal feed. Limited data are collected at the federal or state level concerning the amounts of specific ingredients used in animal feed, and there are insufficient surveillance systems to monitor etiologic agents "from farm to fork."

CONCLUSIONS

Increased funding for integrated veterinary and human health surveillance systems and increased collaboration among feed professionals, animal producers, and veterinary and public health officials is necessary to effectively address these issues.