Survey of quantitative antimicrobial consumption per production stage in farrow-to-finish pig farms in Spain

Alternatives to antibiotics in pig production: looking through the lens of immunophysiology

In the livestock production system, the evolution of porcine gut microecology is consistent with the idea of "The Hygiene Hypothesis" in humans. I.e., improved hygiene conditions, reduced exposure to environmental microorganisms in early life, and frequent use of antimicrobial drugs drive immune dysregulation. Meanwhile, the overuse of antibiotics as feed additives for infectious disease prevention and animal growth induces antimicrobial resistance genes in pathogens and spreads related environmental pollutants. It justifies our attempt to review alternatives to antibiotics that can support optimal growth and improve the immunophysiological state of pigs. In the current review, we first described porcine mucosal immunity, followed by discussions of gut microbiota dynamics during the critical weaning period and the impacts brought by antibiotics usage. Evidence of in-feed additives with immuno-modulatory properties highlighting probiotics, prebiotics, and phytobiotics and their cellular and molecular networking are summarized and reviewed. It may provide insights into the immune regulatory mechanisms of antibiotic alternatives and open new avenues for health management in pig production.

Molecular Characterisation of Antimicrobial Resistance in E. coli Isolates from Piglets in the West Region of Romania

Antibiotics are widely used for prophylaxis and therapy, reducing morbidity and mortality produced by bacterial pathogensin pigs, including infections caused by Escherichia coli. The aim of this study was to characterise antibiotic resistance phenotypes and genotypes in E. coli isolates in pigs in West Romanian grower farms. Differential phenotypic susceptibility profiles and the contribution of resistance genes to phenotypic expression of susceptibility or resistance were evaluated. A total of 76 E. coli isolates were identified and confirmed by the MicroScan Walk Away System. The occurrence of four resistance genes, ampC, blaZ, blaTEM and tetK in strains resistant to 13 antibiotics was assessed. Of the E. coli isolates, 0% showed resistance to meropenem, 3.9% to tigecycline and 10.5% to piperacillin/tazobactam, whereas, in contrast, 100% were resistant to ampicillin and mezlocillin, 76.31% to piperacillin and 59.3% to tetracycline. The prevalence of resistance genes in resistant isolates detected by q-PCR analysis was 97.0% for ampC, 96% for blaZ, 32.9% for blaTEM and 58.8% for tetK. Penetrance (the proportion of individuals carrying a particular variant of a gene that also expresses an associated trait) was 50% for ampC (32% for amoxicillin/clavulanate, 62% for cefazolin, 32% for cefepime, 100% for cefotaxime, 56% for cefuroxime and 99% for ampicillin), 65% for blaZ (32% for amoxicillin/clavulanate and 99% for ampicillin), 51% for blaTEM (81% for piperacillin) and 44% for the tetK gene (83% for tetracycline). The result of phenotypic antibiotic resistance testing may indicate the presence of plasmid-borne resistance, with a diagnostic odds ratio of a positive phenotypic resistance for tetK being 4.52. As a management decision, the maximum penetrance admitted for using a specific antibiotic for E. coli infections in pigs is recommended to be less than 20%.

Use of Antimicrobials by Class in Pigs in Germany-A Longitudinal Description Considering Different International Categorisation Systems

Antimicrobial usage in both human and veterinary medicine is considered one of the main drivers of antimicrobial resistance; its reduction poses a serious challenge. To analyse the associations between usage and resistance, data from monitoring systems and classification of all antimicrobial substances are crucial. In this analysis, we investigated longitudinal data collected between 2013 and 2020 within the Veterinary Consumption of Antibiotics project from pig farms in Germany, including all antimicrobial classes, but focusing on critically important antimicrobials: third- and fourth-generation cephalosporins, fluoroquinolones, macrolides, and polymyxins. Analysing the treatment frequency, we found that a reduction in antimicrobial use in all types of pig production has occurred over time, accompanied by a rising percentage of farms without any usage. The lists of the World Health Organisation, World Organisation for Animal Health, and European Medicine Agency classify different antimicrobial substances as critically important. The vast differences between the respective weighted treatment frequencies allocated to the antimicrobials of main interest reflect the huge impact of the three categorisation systems. We concluded that, with the aim of creating national treatment guidelines supporting veterinarians to make treatment decisions, the list of the European Medicine Agency is the most suitable.

Antibiotic Use in European Pig Production: Less Is More

The goal of this study is to describe the current use of antibiotics in the European pig industry based on an extensive literature review. To achieve this, an overview of results from national (n = 15) and multi-country (n = 2) cross-sectional and longitudinal (n = 2) surveys, which describe antimicrobial use in pigs, is presented. Results are further linked to the outcome of the European Surveillance of Veterinary Antimicrobial Consumption (ESVAC) project. Overall, it was found that weaned piglets received the most antibiotics, followed by suckling piglets resulting in over 80% of the treatments being administered to animals before 10 weeks of age. Furthermore, it was observed that antibiotic use (ABU) was significantly associated across age categories, indicating that farms with a high use in piglets also used more antibiotics in their finishers. This may, among other things, be explained by farmers' habits and behavior. However, above all, the studies showed surprisingly large differences in ABU between the countries. These differences may be related to the differences in disease prevalence and/or differences in the level of biosecurity. However, they may also reflect variations in rules and regulations between countries and/or a difference in attitude towards ABU of farmers and veterinarians that are not necessarily linked to the true animal health situation. Furthermore, it was observed that already a substantial proportion of the European pig production is able to successfully raise pigs without any group treatments, indicating that it is possible to rear pigs without systematic use of antibiotics. Based on the ESVAC data, a decline of 43.2% was observed in sales of antibiotics for animals in Europe between 2011 and 2020. To enable efficient antimicrobial quantification and stewardship, 15 European countries have already established systems for herd level monitoring ABU in pigs.

Updates on the global dissemination of colistin-resistant Escherichia coli: An emerging threat to public health

Colistin drug resistance is an emerging public health threat worldwide. The adaptability, existence and spread of colistin drug resistance in multiple reservoirs and ecological environmental settings is significantly increasing the rate of occurrence of multidrug resistant (MDR) bacteria such as Escherichia coli (E. coli). Here, we summarized the reports regarding molecular and biological characterization of mobile colistin resistance gene (mcr)-positive E. coli (MCRPEC), originating from diverse reservoirs, including but not limited to humans, environment, waste water treatment plants, wild, pets, and food producing animals. The MCRPEC revealed the abundance of clinically important resistance genes, which are responsible for MDR profile. A number of plasmid replicon types such as IncI2, IncX4, IncP, IncX, and IncFII with a predominance of IncI2 were facilitating the spread of colistin resistance. This study concludes the distribution of multiple sequence types of E. coli carrying mcr gene variants, which are possible threat to "One Health" perspective. In addition, we have briefly explained the newly known mechanisms of colistin resistance i.e. plasmid-encoded resistance determinant as well as presented the chromosomally-encoded resistance mechanisms. The transposition of ISApl1 into the chromosome and existence of intact Tn6330 are important for transmission and stability for mcr gene. Further, genetic environment of co-localized mcr gene with carbapenem-resistance or extended-spectrum β-lactamases genes has also been elaborated, which is limiting human beings to choose last resort antibiotics. Finally, environmental health and safety control measures along with spread mechanisms of mcr genes are discussed to avoid further propagation and environmental hazards of colistin resistance.

Antimicrobial Use and Susceptibility of Indicator Escherichia coli in Finnish Integrated Pork Production

In pigs, antimicrobial use (AMU) practices vary at different production phases between herds and between countries. Antimicrobial resistance (AMR) development is linked to AMU but recognized as a multi-factorial issue, and thus, any information increasing knowledge of AMU and AMR relationships is valuable. We described AMU and screened the carriage of different AMR phenotypes of indicator Escherichia coli in 25 selected Finnish piglet-producing and finishing herds that formed nine birth-to-slaughter production lines. Moreover, we studied associations between AMU and AMR in both herd types and throughout the production line. Treatment records were obtained from the national Sikava register for 1year, and AMU was quantified as mg/PCU (population correction unit) and TIs (treatment incidences). For phenotypic antimicrobial susceptibility testing, ten pen-level pooled feces samples (n=250) in each herd were collected from one room representing the oldest weaned piglets or the oldest finishing pigs. Majority of the medications (96.8%) was administered parenterally, and penicillin was the predominant antimicrobial in every herd. More different antimicrobial substances were used in piglet-producing than in finishing herds (median 5 and 1, respectively, p<0.001). As mg/PCU, sows had the highest AMU and suckling piglets had the highest TIs, whereas finishing pigs were the least treated age group. The proportion of susceptible indicator E. coli isolates of all studied isolates was 59.6%. Resistance was found most commonly against tetracycline, sulfamethoxazole, trimethoprim, and ampicillin, and multi-resistant (MR) isolates (46.5% of all resistant isolates) were resistant to a maximum of four different antimicrobials. Quinolone resistance was rare, and no resistance against 3rd-generation cephalosporins, meropenem, azithromycin, colistin, gentamicin, or tigecycline was detected. The main associations between AMU and AMR were found at antimicrobial group level when use was compared with the presence of AMR phenotypes. The proportion of resistant isolates was not associated with AMU, and herd size was not associated with either AMU or AMR. We suggest that the use of narrow-spectrum beta-lactams as a primary treatment option and lack of wide application of oral group medications potentially favors a good resistance pattern in integrated pork production.

Transmission of Similar Mcr-1 Carrying Plasmids among Different Escherichia coli Lineages Isolated from Livestock and the Farmer

Colistin use has mostly been stopped in human medicine, due to its toxicity. However, nowadays, it still is used as a last-resort antibiotic to treat hospital infections caused by multi-drug resistant Enterobacteriaceae. On the contrary, colistin has been used in veterinary medicine until recently. In this study, 210 fecal samples from pigs (n = 57), calves (n = 152), and the farmer (n = 1) were collected from a farm where E. coli harboring mcr-1–mcr-3 was previously detected. Samples were plated, and mcr-genes presence was confirmed by multiplex-PCR. Hybrid sequencing which determined the presence and location of mcr-1, other antibiotic resistance genes, and virulence factors. Eighteen colistin resistant isolates (13 from calves, four from pigs, and one from the farmer) contained mcr-1 associated with plasmids (IncX4, IncI2, and IncHI2), except for two that yielded mcr-1 in the chromosome. Similar plasmids were distributed in different E. coli lineages. Transmission of mcr-1 to the farmer most likely occurred by horizontal gene transfer from E. coli of calf origin, since plasmids were highly similar (99% coverage, 99.97% identity). Moreover, 33 virulence factors, including stx2 for Shiga toxin E. coli (STEC) were detected, highlighting the role of livestock as a reservoir of pathotypes with zoonotic potential.

Colistin Update on Its Mechanism of Action and Resistance, Present and Future Challenges

Colistin has been extensively used since the middle of the last century in animals, particularly in swine, for the control of enteric infections. Colistin is presently considered the last line of defense against human infections caused by multidrug-resistant Gram-negative organisms such as carbapenemase-producer Enterobacterales, Acinetobacter baumanni, and Pseudomonas aeruginosa. Transferable bacterial resistance like mcr-genes was reported in isolates from both humans and animals. Researchers actively seek strategies to reduce colistin resistance. The definition of guidelines for colistin therapy in veterinary and human medicine is thus crucial. The ban of colistin use in swine as a growth promoter and for prophylactic purposes, and the implementation of sustainable measures in farm animals for the prevention of infections, would help to avoid resistance and should be encouraged. Colistin resistance in the human-animal-environment interface stresses the relevance of the One Health approach to achieve its effective control. Such measures should be addressed in a cooperative way, with efforts from multiple disciplines and with consensus among doctors, veterinary surgeons, and environment professionals. A revision of the mechanism of colistin action, resistance, animal and human use, as well as colistin susceptibility evaluation is debated here.

Quantification, description and international comparison of antimicrobial use on Irish pig farms

Background

There is concern that the use of antimicrobials in livestock production has a role in the emergence and dissemination of antimicrobial resistance in animals and humans. Consequently, there are increasing efforts to reduce antimicrobial use (AMU) in agriculture. As the largest consumer of veterinary antimicrobials in several countries, the pig sector is a particular focus of these efforts. Data on AMU in pig production in Ireland are lacking. This study aimed to quantify AMU on Irish pig farms, to identify the major patterns of use employed and to compare the results obtained to those from other published reports and studies.

Results

Antimicrobial use data for 2016 was collected from 67 Irish pig farms which represented c. 35% of national production. The combined sample population consumed 14.5 t of antimicrobial by weight of active ingredient suggesting that the pig sector accounted for approximately 40% of veterinary AMU in Ireland in 2016. At farm level, median AMU measured in milligram per population correction unit (mg/PCU) was 93.9 (range: 1.0–1196.0). When measured in terms of treatment incidence (TI200), median AMU was 15.4 (range: 0.2–169.2). Oral treatments accounted for 97.5% of all AMU by weight of active ingredient and were primarily administered via medicated feed to pigs in the post weaning stages of production. AMU in Irish pig production in 2016 was higher than results obtained from the national reports of Sweden, Denmark, the Netherlands and France but lower than the United Kingdom.

Conclusions

Pig production in Ireland is an important consumer of veterinary antimicrobials. The quantities and patterns of AMU on Irish pig farms are comparable to pig production in other European countries but higher than some countries with more advanced AMU reduction strategies. This AMU is characterised by a high proportion of prophylactic use and is primarily administered to pigs post weaning via medicated feed. Further studies to better understand the reasons for AMU on Irish pig farms and strategies to improve health among weaner pigs will be of benefit in the effort to reduce AMU.

Vultures from different trophic guilds show distinct oral pathogenic yeast signatures and co-occurrence networks

Vultures have evolved adaptive mechanisms to prevent infections associated with their scavenging lifestyle. However, food-borne exposure to antimicrobial pharmaceuticals can promote opportunistic infections with adverse outcomes. Here, we used multivariate and network analyses to increase understanding of the behavior of the yeast communities causing oral mycosis outbreaks recently reported in wild nestling cinereous (Aegypius monachus), griffon (Gyps fulvus) and Egyptian (Neophron percnopterus) vultures (CV, GV and EV, respectively) exposed to antibiotics from livestock farming. Common and unique yeast signatures (of Candida, Debaromyces, Diutina, Meyerozyma, Naganishia, Pichia, Rhodotorula, Trichosporon and Yarrowia species) associated with oral mycoses were identified in the three vulture species. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) highlighted that oral lesions from CV and GV shared similar yeast signatures (of major causative pathogens of opportunistic mycoses, such as Candida albicans, Candida parapsilosis and Candida tropicalis), while EV had a distinct yeast signature (of uncommon pathogenic species, such as Candida dubliniensis, Candida zeylanoides, Pichia fermentans and Rhodotorula spp.). Synergistic interactions between yeast species from distinct fungal phyla were found in lesions from CV and GV, but not in EV. These formed co-occurrence subnetworks with partially or fully connected topology. This study reveals that the composition, assembly and co-occurrence patterns of the yeast communities causing oral mycoses differ between vulture species with distinct feeding habits and scavenging lifestyles. Yeast species widely pathogenic to humans and animals, and yeast co-occurrence relationships, are distinctive hallmarks of oral mycoses in CV and GV. These vulture species are more exposed to antibiotics from intensively medicated livestock carcasses provided in supplementary feeding stations and show higher incidence of thrush-like oral lesions than EV. These findings may be useful for development of new initiatives or changes in the conservation of these avian scavengers affected by anthropogenic activities.

mcr-Colistin Resistance Genes Mobilized by IncX4, IncHI2, and IncI2 Plasmids in Escherichia coli of Pigs and White Stork in Spain

Colistin has become the last-line antimicrobial for the treatment of multidrug resistant (MDR) Enterobacterales in human medicine. To date, several colistin resistance genes have been described. Of them mcr-1 is disseminated worldwide in Escherichia coli of human and animal origin. The aim of this study was to characterize mcr-mediated resistance plasmids from E. coli of animal origin in Spain. From our strain collection, 70 E. coli of pig origin collected between 2005 and 2014 (10 per year, except for years 2009–2010–2013) were randomly selected and screened for the presence of mcr-genes. Additionally, 20 E. coli isolated in 2011 from white storks (Ciconia ciconia) from the same urban household waste landfill associated colony were also included. Whole genome sequencing of mcr-positive isolates was carried out on a MiSeq (Illumina). Hybrid whole genome sequencing strategy combining nanopore and Illumina technologies were performed in a selection of isolates to close the genomes and plasmids and identify the presence of antimicrobial resistance genes. Minimum inhibitory concentration (MIC) was used to assess the susceptibility to colistin. Mating experiments were carried out to evaluate transferability of the mcr-genes. A total of 19 mcr-1 and one mcr-4 positive isolates were detected, 15 from pigs distributed during the study period, and five from storks collected in 2011. No other mcr-variants were found. The MICs for colistin ranged between 4 and >4 mg/L. High diversity of STs were detected among the mcr-1 positive E. coli isolates, with only ST-10 shared between pigs and white storks. Except for one isolate, all were genotypic and phenotypically MDR, and five of them also harbored cephalosporin resistance genes (bla_CTX–M–14, bla_SHV–12, and three bla_CMY–2). mcr-1 genes were mobilizable by conjugation, associated with IncX4, IncHI2, and IncI2 plasmids. In our study, mcr-1 genes have been circulating in pig farms since 2005 harbored by a variety of E. coli clones. Its persistence may be driven by co-selection since plasmids containing mcr-1 also exhibit resistance to multiple drugs used in veterinary medicine. Furthermore, this is the first report of the presence of mcr-1 gene in isolates from white storks in Spain. This finding highlights the potential importance of wildlife that forage at urban household waste landfills in the transmission and spread of colistin resistance genes.

Effect of tetracycline treatment regimens on antibiotic resistance gene selection over time in nursery pigs

Background

The majority of antimicrobials given during the production of pigs are given to nursery pigs. The influence of antimicrobial use on the levels of antimicrobial resistant (AMR) genes is important to quantify to be able to assess the impact of resistance on the food chain and risk to human and animal health.

Results

This study investigated the response on the levels of nine AMR genes to five different treatment strategies with oxytetracycline, and the dynamics of gene abundance over time by following 1167 pigs from five different farms in Denmark.

The results showed no significant difference between treatments and an increase in abundance for the efflux pump encoding tet(A) gene and the genes encoding the ribosomal protection proteins tet(O) and tet(W) tetracycline resistant genes following treatment, while tet(M) showed no response to treatment. However, it was also observed that the levels of tet(O), tet(W), and ermB in some farms would drift more over time compared to a single treatment-course with antibiotic.

Conclusion

This study underlines the large variation in AMR levels under natural conditions and the need for increased investigation of the complex interactions of antimicrobial treatment and other environmental and managerial practices in swine production on AMR gene abundance.

Antimicrobial susceptibility of Pasteurella multocida isolated from sheep and pigs in Spain - Short communication

Pasteurella multocida is responsible for economically important diseases in sheep and pigs. Antimicrobial susceptibility studies are essential for initiating rational and effective empirical therapy of P. multocida infections. In this study we investigated the antimicrobial susceptibility to 18 antimicrobial agents of 156 clinical isolates of P. multocida from sheep (n = 87) and pigs (n = 69) using the microdilution method. Both sheep and pig isolates exhibited low levels of resistance (≤ 15%) to ceftiofur, gentamicin, neomycin, spectinomycin, chlortetracycline, tulathromycin, florfenicol, danofloxacin, and enrofloxacin and trimethoprim/sulphamethoxazole, high resistance rates (> 15% up to 50%) to oxytetracycline, tilmicosin, and tiamulin, and very high resistance rates (> 50%) to tylosin tartrate, clindamycin, and sulphadimethoxine. However, sheep isolates exhibited significantly lower percentages of resistance and lower MIC₉₀ values (P < 0.05) than pig isolates for most of the antimicrobials tested. In addition, sheep isolates exhibited also significantly lower phenotypic antimicrobial resistance diversity (8 resistotypes vs. 30 resistotypes). LAC-LIN-SUL-MAC was the resistotype most frequently detected in sheep (39.1%) and LIN-SUL-MAC in pig isolates (26.1%). The differences in susceptibility patterns could be influenced by the lower use of antimicrobials in the small ruminant industry compared with the pig farming industry.

Carbapenemase-Producing Elizabethkingia Meningoseptica from Healthy Pigs Associated with Colistin Use in Spain

Carbapenems are considered last-resort antimicrobials, especially for treating infections involving multidrug-resistant Gram-negative bacteria. In recent years, extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Gram-negative bacteria have become widespread in hospitals, community settings, and the environment, reducing the range of effective therapeutic alternatives. The use of colistin to treat infection caused by these multi-drug bacteria may favour the selection and persistence of carbapenem-resistant bacteria. In this study, it is described, for the first time to our knowledge, a carbapenemase-producing isolate of Elizabethkingia meningoseptica from healthy pigs in Spain. The isolate we report was recovered during a study to detect colistin-resistant bacteria from faecal samples of healthy food-production animals using a chromogenic selective medium. Unexpectedly, we found an isolate of Elizabethkingia meningoseptica with high Minimum Inhibitory Concentration (MIC) values for several antibiotics tested. Molecular analysis did not show any mcr family genes related with colistin resistance, but two carbapenemase genes, blaB-12_1 and blaGOB-17_1, were detected. This finding in healthy animals could suggest that colistin may favour the selection and persistence of carbapenem-resistant bacteria.

Antimicrobial susceptibility and genetic characterization of Trueperella pyogenes isolates from pigs reared under intensive and extensive farming practices

Trueperella pyogenes is an opportunistic pathogen associated with a variety of diseases and responsible for important economic losses for pig production. Minimal Inhibitory Concentration (MIC) and Pulsed Field Gel Electrophoresis (PFGE) typing analysis were used to determine the MIC distribution and to genetically characterize a total of 180 T. pyogenes isolates obtained from slaughtered pigs reared under intensive (TpIN, n = 89) and extensive (TpEX, n = 91) farming practices. Low MIC₉₀ values for penicillin and amoxicillin (0.008 and 0.06 μg/ml, respectively), ceftiofur, gentamicin and enrofloxacin (1 μg/ml, respectively) were obtained, so they could be of choice for the empiric treatment of T. pyogenes infections. Except for the penicillin, amoxicillin and ceftiofur, a statistically significant difference was observed in the MIC distribution of all antimicrobials analysed between TpIN and TpEX isolates. Also, MIC₉₀ values were higher in TpIN than in TpEX isolates for neomycin and streptomycin (32 μg/ml vs 8 μg/ml), sulfamethoxazole/trimethoprim (30.4/1.6 μg/ml vs 1.90/0.10 μg/ml) and tylosin (≥1024 μg/ml vs 1 μg/ml). A relatively lower genetic diversity was detected in TpIN in comparison with TpEX isolates (GD 0.42 and GD 0.47, respectively). All isolates were distributed in three clusters (A, B, C). TpIN isolates were statistically associated with cluster A (P = 0.0002; OR 3.21; CI₉₅ 1.74-5.93), whereas the TpEX were distributed throughout the dendrogram, showing more genetic diversity. These data suggest that the antimicrobial susceptibility and genetic variability of the T. pyogenes isolates could be influenced by the management systems.

Effects of zinc supplementation on Shiga toxin 2e-producing Escherichia coli in vitro

Swine edema disease is caused by Shiga toxin (Stx) 2e–producing Escherichia coli (STEC). Addition of highly concentrated zinc formulations to feed has been used to treat and prevent the disease, but the mechanism of the beneficial effect is unknown. The purpose of the present study was to investigate the effects of highly concentrated zinc formulations on bacterial growth, hemolysin production, and an Stx2e release by STEC in vitro. STEC strain MVH269 isolated from a piglet with edema disease was cultured with zinc oxide (ZnO) or with zinc carbonate (ZnCO₃), each at up to 3,000 ppm. There was no effect of zinc addition on bacterial growth. Nonetheless, the cytotoxic activity of Stx2e released into the supernatant was significantly attenuated in the zinc-supplemented media compared to that in the control, with the 50% cytotoxic dose values of 163.2 ± 12.7, 211.6 ± 33.1 and 659.9 ± 84.2 after 24 hr of growth in the presence of ZnO, ZnCO₃, or no supplemental zinc, respectively. The hemolytic zones around colonies grown on sheep blood agar supplemented with zinc were significantly smaller than those of colonies grown on control agar. Similarly, hemoglobin absorbance after exposure to the supernatants of STEC cultures incubated in sheep blood broth supplemented with zinc was significantly lower than that resulting from exposure to the control supernatant. These in vitro findings indicated that zinc formulations directly impair the factors associated with the virulence of STEC, suggesting a mechanism by which zinc supplementation prevents swine edema disease.

Antibiotic drug usage in pigs in Germany-Are the class profiles changing?

The development of antimicrobial resistance is triggered by the use of antibiotic drugs. Therefore, the consumption of antibiotics in livestock is monitored, and different measures may be applied if the usage of antibiotic drugs seems inappropriate. Unfortunately, the surveillance of antibiotic consumption is not standardised, and surveillance systems differ. In Germany, the food quality assurance system QS Qualität und Sicherheit GmbH (QS) began the documentation of antibiotic drug usage in pigs in 2012 in a private economic based database, and for its members, documentation has been mandatory in all pig age groups since 2014. In this investigation, we calculated the distribution of the antibiotics use per pig age group and half-year, and the percentage of the active substances used from overall treatments within German pig holdings from 1 July, 2013 to 30 June, 2015. In fattening pigs, the median of the treatment frequency is 4.3 in 2013-2 and exhibits a decreasing trend in this time period up to 2.1 in 2015-1. In weaners the median ranged between 11.3 in 2014-2 and 5.8 in 2013-2. The median of sucklers varies between 21.6 and 25.0. In sucklers and weaners, a clear temporal trend is not seen to date. The share of the active substances differs between the age groups. In fattening pigs, mostly tetracyclines and penicillines were used, occurring in approximately 60% of the total treatments. In weaners, amoxicillin and colistin have the highest shares of the treatment frequency, at approximately 60%. The treatment frequencies of macrolides and penicillines have the highest share in sucklers.

Colistin in Pig Production: Chemistry, Mechanism of Antibacterial Action, Microbial Resistance Emergence, and One Health Perspectives

Colistin (Polymyxin E) is one of the few cationic antimicrobial peptides commercialized in both human and veterinary medicine. For several years now, colistin has been considered the last line of defense against infections caused by multidrug-resistant Gram-negative such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Colistin has been extensively used orally since the 1960s in food animals and particularly in swine for the control of Enterobacteriaceae infections. However, with the recent discovery of plasmid-mediated colistin resistance encoded by the mcr-1 gene and the higher prevalence of samples harboring this gene in animal isolates compared to other origins, livestock has been singled out as the principal reservoir for colistin resistance amplification and spread. Co-localization of the mcr-1 gene and Extended-Spectrum-β-Lactamase genes on a unique plasmid has been also identified in many isolates from animal origin. The use of colistin in pigs as a growth promoter and for prophylaxis purposes should be banned, and the implantation of sustainable measures in pig farms for microbial infection prevention should be actively encouraged and financed. The scientific research should be encouraged in swine medicine to generate data helping to reduce the exacerbation of colistin resistance in pigs and in manure. The establishment of guidelines ensuring a judicious therapeutic use of colistin in pigs, in countries where this drug is approved, is of crucial importance. The implementation of a microbiological withdrawal period that could reduce the potential contamination of consumers with colistin resistant bacteria of porcine origin should be encouraged. Moreover, the management of colistin resistance at the human-pig-environment interface requires the urgent use of the One Health approach for effective control and prevention. This approach needs the collaborative effort of multiple disciplines and close cooperation between physicians, veterinarians, and other scientific health and environmental professionals. This review is an update on the chemistry of colistin, its applications and antibacterial mechanism of action, and on Enterobacteriaceae resistance to colistin in pigs. We also detail and discuss the One Health approach and propose guidelines for colistin resistance management.

Guidance on the Selection of Appropriate Indicators for Quantification of Antimicrobial Usage in Humans and Animals

An increasing variety of indicators of antimicrobial usage has become available in human and veterinary medicine, with no consensus on the most appropriate indicators to be used. The objective of this review is therefore to provide guidance on the selection of indicators, intended for those aiming to quantify antimicrobial usage based on sales, deliveries or reimbursement data. Depending on the study objective, different requirements apply to antimicrobial usage quantification in terms of resolution, comprehensiveness, stability over time, ability to assess exposure and comparability. If the aim is to monitor antimicrobial usage trends, it is crucial to use a robust quantification system that allows stability over time in terms of required data and provided output; to compare usage between different species or countries, comparability must be ensured between the different populations. If data are used for benchmarking, the system comprehensiveness is particularly crucial, while data collected to study the association between usage and resistance should express the exposure level and duration as a measurement of the exerted selection pressure. Antimicrobial usage is generally described as the number of technical units consumed normalized by the population at risk of being treated in a defined period. The technical units vary from number of packages to number of individuals treated daily by adding different levels of complexity such as daily dose or weight at treatment. These technical units are then related to a description of the population at risk, based either on biomass or number of individuals. Conventions and assumptions are needed for all of these calculation steps. However, there is a clear lack of standardization, resulting in poor transparency and comparability. By combining study requirements with available approaches to quantify antimicrobial usage, we provide suggestions on the most appropriate indicators and data sources to be used for a given study objective.

Influence of porcine circovirus type 2 vaccination on the level of antimicrobial consumption on 65 Austrian pig farms

The administration of antibiotics to farm animals is an important contemporary topic. Veterinarians, pig producers, politicians, retailers and consumers all have a vested interest in reducing antimicrobial use on farm, while ensuring adequate health and welfare of food-producing animals. Vaccination programmes may be used to reduce the overall level of clinical disease in a population, subsequently leading to a decline in antimicrobial use. In 2008, a vaccination programme against porcine circovirus type 2 (PCV-2) was initiated in Austria. In the retrospective observational study presented here, farm medication records (2008-2011) from 65 conventional pig farms were evaluated. As PCV-2 has been shown to lead to generalised immunosuppression, enabling secondary bacterial infections to occur, the authors hypothesised that PCV-2 vaccination would decrease antimicrobial consumption at farm level. Firstly, we focused on the annual antimicrobial consumption expressed as the number of administered animal daily doses per kg liveweight (nADDkg/kg/year). Secondly, a linear mixed effects model was applied to evaluate the influence of PCV-2 vaccination on the antimicrobial consumption at farm level. The interaction between farm type and PCV-2 vaccination was found to be a highly significant factor (P=0.0002) influencing antimicrobial use at farm level. The estimated impact of PCV-2 vaccination revealed a highly significant (P<0.001) decline in total antimicrobial drug use from 1.72 ADDkg/kg/year to 0.56 ADDkg/kg/year on finishing farms, whereas only a negligible decline was detectable on farrow-to-finish farms.

Risk factors for oral antimicrobial consumption in Swiss fattening pig farms - a case-control study

Background

Antimicrobial consumption in veterinary medicine is of great importance. Increased awareness by the public and media has led to demands for decreased use of antimicrobials in pigs. This study aimed to identify risk factors for regular oral antimicrobial consumption in Swiss fattening pig farms, and to quantify the amount of antimicrobial active substances administered orally to pigs at the farm level.

Results

A case–control study was performed on 99 fattening farms between May 2014 and January 2015. Seventy-two case farms (with oral group treatment of antimicrobials in at least 50 % of pigs) and 27 control farms (with no regular oral group treatment) were visited once during the study. Data about potential risk factors and antimicrobial consumption were collected by questionnaire. Antimicrobial consumption was recorded and treatment incidence (TI) was calculated for all farms over a one year period. Sulphonamides and tetracyclines were the antimicrobials consumed in the greatest quantity. The median TI for oral antimicrobial use in the case group was 224.7. In the control group, the median TI was 0 for oral antimicrobial use, with values ranging from 0 to 140.1. In a multivariable regression model, seven risk factors associated with regular oral antimicrobial group treatment were identified: mixing pigs from different suppliers within the same pen, absence of a work protocol that ensures treating of healthy pigs before sick pigs, distance to next pig farm < 500 metres, external analysis of production parameters, no availability of dirty visitor boots, the farmer not working on other farms, and no application of homoeopathic agents.

Conclusions

The results of this study point out the importance of increasing farmers’ awareness of good farming practices and biosecurity. Important recommendations for decreasing oral antimicrobial consumption identified by this study include avoiding mixing pigs from different suppliers in the same pen and strictly handling sick pigs after healthy ones. Improvements in these areas could enhance the overall health of pigs and thereby reduce the consumption of antimicrobials on pig farms.

Wildlife contamination with fluoroquinolones from livestock: Widespread occurrence of enrofloxacin and marbofloxacin in vultures

There is much recent interest in the presence and impact of veterinary pharmaceuticals in wildlife. Livestock carcasses are often disposed of in supplementary feeding stations for avian scavengers, as a management and conservation tool for these species worldwide. In feeding stations, vultures and other scavengers can consume carcasses almost immediately after disposal, which implies the potential ingestion of veterinary pharmaceuticals as a non-target consequence of supplementary feeding. Using UPLC-MS/MS and HPLC-TOF, we evaluated the presence and concentration of fluoroquinolone residues in plasma of nestling vultures feeding on domestic livestock carrion. Three different fluoroquinolones (marbofloxacin, enrofloxacin and its metabolite ciprofloxacin) and a non-targeted β-lactam (nafcillin) were detected in vulture plasma. The high proportion of individuals (92%) with fluoroquinolone residues at variable concentrations (up to ∼20 μg L(-1) of enrofloxacin and ∼150 μg L(-1) of marbofloxacin) sampled in several geographically distant colonies and on different dates suggests that these and other drugs were potentially ingested throughout nestling development. Contamination with veterinary fluoroquinolones and other pharmaceuticals should be considered as an unintended but alarming consequence of food management in threatened wildlife.

Impact of the use of β-lactam antimicrobials on the emergence of Escherichia coli isolates resistant to cephalosporins under standard pig-rearing conditions

The aim of this study was to evaluate if the treatments with ceftiofur and amoxicillin are risk factors for the emergence of cephalosporin resistant (CR) E. coli in a pig farm during the rearing period. One hundred 7-day-old piglets were divided into two groups, a control (n = 50) group and a group parenterally treated with ceftiofur (n = 50). During the fattening period, both groups were subdivided in two. A second treatment with amoxicillin was administered in feed to two of the four groups, as follows: group 1 (untreated, n = 20), group 2 (treated with amoxicillin, n = 26), group 3 (treated with ceftiofur, n = 20), and group 4 (treated with ceftiofur and amoxicillin, n = 26). During treatment with ceftiofur, fecal samples were collected before treatment (day 0) and at days 2, 7, 14, 21, and 42 posttreatment, whereas with amoxicillin, the sampling was extended 73 days posttreatment. CR E. coli bacteria were selected on MacConkey agar with ceftriaxone (1 mg/liter). Pulsed-field gel electrophoresis (PFGE), MICs of 14 antimicrobials, the presence of cephalosporin resistance genes, and replicon typing of plasmids were analyzed. Both treatments generated an increase in the prevalence of CR E. coli, which was statistically significant in the treated groups. Resistance diminished after treatment. A total of 47 CR E. coli isolates were recovered during the study period; of these, 15 contained blaCTX-M-1, 10 contained blaCTX-M-14, 4 contained blaCTX-M-9, 2 contained blaCTX-M-15, and 5 contained blaSHV-12. The treatment with ceftiofur and amoxicillin was associated with the emergence of CR E. coli during the course of the treatment. However, by the time of finishing, CR E. coli bacteria were not recovered from the animals.

Antimicrobial drug use in Austrian pig farms: plausibility check of electronic on-farm records and estimation of consumption

Electronic drug application records from farmers from 75 conventional pig farms were revised and checked for their plausibility. The registered drug amounts were verified by comparing the farmers' records with veterinarians' dispensary records. The antimicrobial consumption was evaluated from 2008 to 2011 and expressed in weight of active substance(s), number of used daily doses (nUDD), number of animal daily doses (nADD) and number of product-related daily doses (nPrDD). All results were referred to one year and animal bodyweight (kg biomass). The data plausibility proof revealed about 14 per cent of unrealistic drug amount entries in the farmers' records. The annual antimicrobial consumption was 33.9 mg/kg/year, 4.9 UDD_kg/kg/year, 1.9 ADD_kg/kg/year and 2.5 PrDD_kg/kg/year (average). Most of the antimicrobials were applied orally (86 per cent) and at group-level. Main therapy indications were metaphylactic/prophylactic measures (farrow-to-finish and fattening farms) or digestive tract diseases (breeding farms). The proportion of the ‘highest priority critically important antimicrobials’ was low (12 per cent). After determination of a threshold value, farms with a high antimicrobial use could be detected. Statistical tests showed that the veterinarian had an influence on the dosage, the therapy indication and the active substance. Orally administered antimicrobials were mostly underdosed, parenterally administered antimicrobials rather correctly or overdosed.