Antimicrobial prescription data in Danish national database validated against treatment records in organic pig farms and analysed for associations with lesions found at slaughter

Diseases associated with antimicrobial use in pig farms and risk factors thereof: A cross-sectional study in the Netherlands

BACKGROUND

Current antimicrobial use (AMU) in Dutch pig farms is driven by herd health status, as only therapeutic AMU is permitted. This study focused on weaners and sows with suckling piglets to examine the diseases associated with i) overall AMU (measured in Defined Daily Dosage Animal per year - DDDA/Y), ii) use/not use of specific antimicrobial classes, iii) total consumption of specific antimicrobial classes (in DDDA/Y), and iv) farm characteristics linked to the occurrence of diseases that require AMU.

METHODS

Cross-sectional data on AMU, disease aetiologies for group treatments, and farm characteristics were collected from 154 Dutch pig farms, representing the situation in 2019. Associations between disease occurrence as a predictor and AMU (overall and by antimicrobial class) as an outcome were analyzed using multivariable generalized linear regression models. Subsequently, mixed-effects conditional Random Forest analysis was used to identify farm characteristics associated with these diseases.

RESULTS

Group treatments for musculoskeletal/neurological diseases (MNDs) in suckling piglets, and individual treatments (of unknown aetiology) in sows and suckling piglets, were significantly associated with total AMU there. AMU in weaners was significantly associated with respiratory diseases, MNDs, and individual treatments. Tetracyclines and penicillins were primarily used for respiratory diseases and MNDs in weaners, respectively, and for MNDs in sows and suckling piglets. Having a clear separation between clean and dirty outdoor areas in the farm and using boars from own production for estrus detection were both protective against occurrence of respiratory conditions in weaners, whereas PRRS vaccination in suckling piglets was a risk factor. Streptococcus suis vaccination in sows and fully slatted floors were both risk factors for MNDs in weaners, whereas being an organic farm was protective. Use of disinfecting powders in sows increased MNDs risk in suckling piglets and sows, and a longer lactation period was protective against respiratory diseases and MNDs in weaners.

CONCLUSIONS

Respiratory diseases and MNDs in weaners appeared as the primary aetiologies for antimicrobial group treatments on Dutch pig farms. Prioritizing farm practices that enhance biosecurity and animal welfare is crucial for controlling these diseases and, consequently, reducing AMU.

Distribution of Antimicrobial Resistance and Biofilm Production Genes in the Genomic Sequences of S. aureus: A Global In Silico Analysis

Background:Staphylococcus aureus constitutes a significant public health threat due to its exceptional adaptability, antimicrobial resistance (AMR), and capacity to form biofilms, all of which facilitate its persistence in clinical and environmental settings. Methods: This study undertook an extensive in silico analysis of 44,069 S. aureus genomic sequences acquired from the NCBI database to assess the global distribution of biofilm-associated and resistance-associated genes. The genomes were categorized into human clinical and environmental groups, with clinical samples representing a predominant 96%. Results: The analysis revealed notable regional discrepancies in sequencing efforts, with Europe and North America contributing 76% of the genomes. Key findings include the high prevalence of the ica locus, which is associated with biofilm formation, and its robust correlation with other genes, such as sasG, which was exclusively linked to SCCmec type IIa. The AMR gene analysis revealed substantial genetic diversity within environmental samples, with genes like vga(E) and erm being identified as particularly prominent. The clonal complex analysis revealed ST8 (USA300) and ST5 as the predominant types in human clinical isolates, while ST398 and ST59 were most frequently observed in environmental isolates. SCCmec type IV was globally prevalent, with subtype Iva being strongly associated with ST8 in North America and subtype IVh with ST239 in Europe. Conclusions: These findings underscore the dynamic evolution of S. aureus via mobile genetic elements and highlight the necessity for standardized metadata in public genomic databases to improve surveillance efforts. Furthermore, they reinforce the critical need for a One Health approach in monitoring S. aureus evolution, particularly concerning the co-dissemination of biofilm and resistance genes across various ecological niches.

An Integrated Analysis of Abattoir Lung Lesion Scores and Antimicrobial Use in Italian Heavy Pig Finishing Farms

Respiratory diseases significantly affect intensive pig finishing farms, causing production losses and increased antimicrobial use (AMU). Lesion scoring at slaughter has been recognized as a beneficial practice to evaluate herd management. The integrated analysis of abattoir lesion scores and AMU data could improve decision-making by providing feedback to veterinarians and farmers on the effectiveness of antimicrobial treatments, thus rationalizing their use. This study compared lung and pleural lesion scores collected at Italian pig slaughterhouses with on-farm AMU, estimated through a treatment index per 100 days (TI100). Overall, 24,752 pig carcasses, belonging to 236 batches from 113 finishing farms, were inspected. Bronchopneumonia and chronic pleuritis were detected in 55% and 48% of the examined pigs, respectively. Antimicrobials were administered in 97% of the farms during the six months prior to slaughter (median TI100 = 5.2), notwithstanding compliance with the mandatory withdrawal period. EMA category B (critical) antimicrobials were administered in 15.2% of cases (median TI100 = 0.06). The lung score was not associated with the total AMU, but significant, positive associations were found with the past use of critical antimicrobials (p = 0.041) and macrolides (p = 0.044). This result highlights the potential of abattoir lung lesion monitoring to rationalize antimicrobial stewardship efforts, contributing to AMU reduction.

Antibacterial plant combinations prevent postweaning diarrhea in organically raised piglets challenged with enterotoxigenic Escherichia coli F18

Antibiotics and zinc oxide restrictions encourage the search for alternatives to combat intestinal pathogens, including enterotoxigenic Escherichia coli (ETEC), a major cause of postweaning diarrhea (PWD) in pigs. PWD causes important economic losses for conventional and organic farming. This study investigated the effect of dietary supplementation with garlic and apple pomace or blackcurrant on infection indicators and the fecal microbiota of organic-raised piglets challenged with ETEC-F18. For 21 days, 32 piglets (7-weeks-old) were randomly assigned to one of four groups: non-challenge (NC); ETEC-challenged (PC); ETEC-challenged receiving garlic and apple pomace (3 + 3%; GA); ETEC-challenged receiving garlic and blackcurrant (3 + 3%; GB). ETEC-F18 was administered (8 mL; 109 CFU/ml) on days 1 and 2 postweaning. The 1st week, PC had lower average daily gain than those in the NC, GA, and GB groups (P < 0.05). NC pigs showed neither ETEC-F18 shedding nor signs of diarrhea. The PC group had higher diarrhea incidence and lower fecal dry matter than NC (≈5–10 days; 95% sEBCI). The GA and GB groups showed reduced ETEC-F18 and fedA gene shedding, higher fecal dry matter, and lower diarrhea incidence than the PC (≈5–9 days; 95% sEBCI). The NC, GA, and GB had normal hematology values during most of the study, whereas the PC had increased (P < 0.05) red blood cells, hemoglobin, and hematocrit on day 7. Haptoglobin and pig-MAP increased in all groups, peaking on day 7, but PC showed the greatest increase (P < 0.05). The fecal microbiota of PC pigs had reduced α-diversity (day 7; P < 0.05) and higher volatility (days 3–14; P < 0.05). Escherichia, Campylobacter, and Erysipelothrix were more abundant in the PC than in the NC, GB, and GA groups (log2FC > 2; P < 0.05), whereas Catenibacterium, Dialister, and Mitsoukella were more abundant in the NC, GB, and GA than in the PC group (log2FC > 2; P < 0.05). Prevotella and Lactobacillus were more abundant in the GB group (log2FC > 2, P < 0.05). In conclusion, dietary supplementation of GA and GB limited ETEC proliferation, reduced PWD, and beneficially impacted the fecal microbiota's diversity, composition, and stability.

Neomycin resistance in clinical Escherichia coli from Danish weaner pigs is associated with recent neomycin use and presence of F4 or F18 fimbriaes

Neomycin is a first-choice antibiotic for treatment of porcine enteritis caused by enterotoxigenic Escherichia coli (ETEC), but little is known about factors influencing resistance to this drug. The aims of this study were to assess antimicrobial resistance and virulence in 325 E. coli isolates obtained in 2020 from various infections in pigs, and to identify factors associated with neomycin resistance development. Susceptibility to 16 antimicrobial agents was determined by broth microdilution, and occurrence of ETEC-associated virulence factors was screened by PCR and hemolysis on blood agar. Univariate and multivariate logistic regression analyses were performed to determine if age group, virulence factors, or antibiotic use (neomycin and other antibiotics) were associated with neomycin resistance. STa, STb, LT, F4, and F18 were detected in 14%, 37%, 26%, 21% and 23% of the isolates, respectively. Resistance was low for antimicrobials of high public health importance (1.5% for cefotaxime, 1% for colistin and no fluoroquinolone resistance) but high for drugs used for treatment of ETEC enteritis (e.g. 20% for neomycin). Isolates with the ETEC pathotype were significantly associated with the weaner age group and intestinal/fecal origin. Multivariate analysis showed that recent neomycin use and presence of F4 or F18 were significantly associated with neomycin resistance amongst isolates from weaners. These results prove an association between neomycin resistance and use at the farm level. Further research is warranted to determine why neomycin resistance was associated with F4 and F18, and whether neomycin use may co-select for virulent strains.

Risk Factors for Antimicrobial Use on Irish Pig Farms

Simple Summary

Antimicrobial resistance (AMR) is a major threat to public health. There are concerns that antimicrobial use (AMU) in agriculture has a role in the development of AMR. Pigs are one of the main consumers of veterinary antimicrobials and a better understanding of the drivers for AMU in this sector will help in efforts to reduce use. The aim of this study was to investigate the associations between antimicrobial use, farm characteristics, biosecurity, the presence of respiratory disease on the farm and health management practices on Irish pig farms. Farms that manufactured their feed on-site had lower total AMU than farms that purchased their feed from a feed mill. Higher levels of lung abscesses and pericarditis (inflammation of the lining around the heart), both indicators of respiratory disease, were associated with increased AMU. Higher levels of pericarditis were also associated with increased use of critically important antimicrobials. Farms vaccinating against swine influenza also had higher AMU. Farms that administered prophylactic antimicrobial treatments to piglets had higher use of individual treatments and critically important antimicrobials. The results from this study show that prophylaxis and respiratory disease are the main drivers of AMU on Irish pig farms. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.

Abstract

The threat to public health posed by antimicrobial resistance in livestock production means that the pig sector is a particular focus for efforts to reduce antimicrobial use (AMU). This study sought to investigate the risk factors for AMU in Irish pig production. Antimicrobial use data were collected from 52 farrow-to-finish farms. The risk factors investigated were farm characteristics and performance, biosecurity practices, prevalence of pluck lesions at slaughter and serological status for four common respiratory pathogens and vaccination and prophylactic AMU practices. Linear regression models were used for quantitative AMU analysis and risk factors for specific AMU practices were investigated using logistic regression. Farms that milled their own feed had lower total AMU (p < 0.001), whereas higher finisher mortality (p = 0.043) and vaccinating for swine influenza (p < 0.001) increased AMU. Farms with higher prevalence of pericarditis (p = 0.037) and lung abscesses (p = 0.046) used more group treatments. Farms with higher prevalence of liver milk spot lesions (p = 0.018) and farms practising prophylactic AMU in piglets (p = 0.03) had higher numbers of individual treatments. Farms practising prophylactic AMU in piglets (p = 0.002) or sows (p = 0.062) had higher use of cephalosporins and fluoroquinolones. This study identified prophylactic use and respiratory disease as the main drivers for AMU in Irish pig production. These findings highlight areas of farm management where interventions may aid in reducing AMU on Irish pig farms.