For proper treatment of bacterial infections in mink, knowledge of the causative agents and their antimicrobial susceptibility patterns is crucial. The used antimicrobials are in general not registered for mink, i.e. most usage is “off-label”. In this study, we report the patterns of antimicrobial resistance among pathogenic bacteria isolated from Danish mink during the period 2014–2016. The aim of this investigation was to provide data on antimicrobial resistance and consumption, to serve as background knowledge for new veterinary guidelines for prudent and optimal antimicrobial usage in mink. A total number of 308 Escherichia coli isolates, 41 Pseudomonas aeruginosa, 36 Streptococcus canis, 30 Streptococcus dysgalactiae, 55 Staphylococcus delphini, 9 Staphylococcus aureus, and 20 Staphylococcus schleiferi were included in this study. Among E. coli, resistance was observed more frequently among the hemolytic isolates than among the non-hemolytic ones. The highest frequency of resistance was found to ampicillin, 82.3% and 48.0% of the hemolytic of the non-hemolytic isolates, respectively. The majority of the P. aeruginosa isolates were only sensitive to ciprofloxacin and gentamicin. Among the Staphylococcus spp., the highest occurrence of resistance was found for tetracycline. Regarding the nine S. aureus, one isolate was resistant to cefoxitin indicating it was a methicillin-resistant Staphylococcus aureus. Both β-hemolytic Streptococcus species showed high levels of resistance to tetracycline and erythromycin. The antimicrobial consumption increased significantly during 2007–2012, and fluctuated at a high level during 2012–2016, except for a temporary drop in 2013–2014. The majority of the prescribed antimicrobials were aminopenicillins followed by tetracyclines and macrolides. The study showed that antimicrobial resistance was common in most pathogenic bacteria from mink, in particular hemolytic E. coli. There is a need of guidelines for prudent use of antimicrobials for mink.

Antibiotic consumption is considered to be a main driver of antibiotic resistant bacteria. Mink breeding follows a distinctive seasonal reproduction cycle, and all of the mink produced in the northern hemisphere are bred, born, and pelted around the same time of year. Some of the diseases are age-related, which is reflected in the seasonal variation of antibiotic consumption. The seasonality makes mink a good model for the investigation of the association between antibiotic consumption and resistance. The objectives of this study were (1) to monitor the farm level of antibiotic resistance during one production cycle and (2) to assess the potential associations between antibiotic consumption and resistance. Twenty-four farms were included in this study (Denmark n = 20, Iceland n = 2, and The Netherlands n = 2), following a cohort of animals born in 2018. Staphylococcus delphini and Escherichia coli were isolated from samples of the carcasses and faeces and were collected randomly. The isolates were susceptibility tested and subsequently divided into the sensitive wildtype (WT) and the resistant non-wildtype (NWT) populations. The antibiotic consumption relative to the sampling periods was assessed as having a short-term or a long-term impact, i.e., in two explanatory factors. For both S. delphini and E. coli, a large between-farm variation of NWT profiles was detected. In the final multivariable, generalized linear mixed models, significant associations between NWT isolates and the consumption of specific antibiotics were found: the short-term use of tetracyclines in the growth period was associated with the occurrence of tetracycline NWT E. coli in the growth period (OR: 11.94 [1.78; 89.28]), and the long-term use of macrolide and tetracyclines was associated with the occurrence of erythromycin NWT S. delphini in the weaning period (OR: 18.2 [2.26; 321.36]) and tetracycline NWT S. delphini in the growth period (OR: 8.2 [1.27; 63.31]), respectively. Farms with zero consumption in the study years prior to sampling also had a substantial proportion of NWT isolates, indicating that NWT isolates are persistent and/or widely spread in the environment. Generally, a high occurrence of tetracycline NWTs was observed. NWT isolates with resistance against the most commonly used antibiotics were found on all the farms, stressing the need for routine surveillance and the prudent use of antibiotics. The results offer a preview of the complex relationship between consumption and resistance, demonstrating some significant associations between use and resistance. Moreover, antibiotic-resistant bacteria are present even on farms with no antibiotic consumption over extended periods, and theoretical explanations supported by the data are offered.

Streptococcus phocae infection has been described in salmon, sea otters, and several families of pinnipeds. The pathology of the infected animals has mainly been located in the respiratory tract and reproductive system, and with indications of septicemia. In this study, we report the finding of S. phocae in diagnostic material from three unrelated cases of farmed mink. Since S. phocae initially has been described in pinnipeds, two isolates from wild harbor seals were included. All isolates originated from Denmark. To our knowledge, this is the first report of S. phocae infection in mink. The animals (three mink, two seals) were necropsied, and samples were collected for bacteriology, virology, and histopathology. Additionally, the S. phocae isolates were whole genome sequenced and compared to sequences of previously reported isolates from other host species. S. phocae was isolated from the lungs of one mink and one seal with bacteremia, and from one seal with pneumonia. The two remaining mink had dermal infections on the paws and S. phocae was isolated from the lesions. The analysis of the sequence data showed that the three mink isolates and one seal isolate were closely related. Further investigation is needed to conclude whether S. phocae is establishing as commensal in farmed mink and to uncover the infection related pathology in mink. Streptococcus phocae has been described as an emerging pathogen in other species, therefore future awareness and surveillance of this pathogen is crucial.

Optimizing antimicrobial dosage regimens and development of breakpoints for antimicrobial susceptibility testing are important prerequisites for rational antimicrobial use. The objectives of the study were (1) to produce MIC data for four mink pathogens and (2) to employ these MIC data to support the development of tentative epidemiological cut-off values (TECOFFs), which may be used for future development of mink-specific antimicrobial dosages and breakpoints. Broth microdilution was used to establish MIC distributions for 322 mink bacterial isolates of clinical origin from six European mink-producing countries. The included species were E. coli (n = 162), S. delphini (n = 63), S. canis (n = 42), and P. aeruginosa (n = 55). Sixty-four E. coli isolates and 34 S. delphini isolates were whole-genome sequenced and analyzed for antimicrobial resistance genes. No EUCAST MIC data are available on S. delphini and S. canis, hence tentative ECOFFs were suggested for the majority of the tested antimicrobials. For E. coli and P. aeruginosa, the wildtype distributions were in accordance with EUCAST data. Overall, the genotypes of the sequenced isolates were in concordance with the phenotypes. These data constitute an important piece in the puzzle of developing antimicrobial dosages and clinical breakpoints for mink. Until pharmacokinetic and clinical data become available, the (tentative) ECOFFs can be used for monitoring resistance development and as surrogates for clinical breakpoints.

There is a need for large-animal fracture models focusing on small tubular bones, as existing models typically involve major weight-bearing bones and often rely on restrictive suspension systems that raise significant animal welfare concerns. This study presents a novel in vivo sheep model targeting the proximal phalanx, designed to enable natural movement and social housing whilst supporting the investigation of fracture fixation and bone healing. Eleven skeletally mature Texel sheep were included; four underwent bilateral ostectomies with 3 mm or 6 mm defects, and seven received an osteotomy. A hoof block was used to offload the affected digit, enabling the sheep to move freely and to be housed in pairs. Bone healing was assessed using standardised radiographic scoring based on images obtained intraoperatively, at week 1 and 2, and hereafter every second week. Hard callus thickness was assessed at the end of the study period by a computed tomography-based method. Animal welfare was monitored through repeated clinical evaluations, two pain scoring systems (a validated sheep facial pain expression scale and a novel composite behavioural pain score), and biomarkers of inflammation, including serum amyloid A and haptoglobin. The ostectomy group showed frequent implant failure and limited healing, particularly in the 6 mm ostectomies, whilst the osteotomy group demonstrated relatively better stability and more consistent healing. Pain scores peaked shortly after surgery and again following withdrawal of analgesia but remained generally low. This study presents a novel, welfare-consciousness bilateral ovine proximal phalanx fracture model that challenges osteosynthesis stability. The integrated multimodal welfare assessment highlights the importance of objective pain and stress monitoring and advocates for the routine inclusion of quantitative welfare parameters alongside bone healing outcomes in translational orthopedic research.

A novel composite patch osteosynthesis technique (CPT) has demonstrated promising ex vivo biomechanical performance in small tubular bones. To bridge the gap toward clinical evaluations, this study compared the stability of the CPT to a stainless-steel locking plate (LP) in an experimental in vivo ovine bilateral proximal phalanx fracture model. Eight sheep underwent a midline osteotomy with a 4.5 mm circular unicortical defect in the lateral proximal phalanx of both front limbs, treated with the CPT (n = 8) or the LP (n = 8). A half-limb walking cast, or a custom off-loading hoof shoe, was used for postoperative protection. Implant stability was assessed by post-surgery X-ray evaluations and post-euthanasia (16 weeks) dual-energy X-ray absorptiometry (DXA). At week one, all CPT implants demonstrated mechanical failure, while all LPs remained overall intact. Mean BMD was 0.45 g/cm² for CPT and 0.60 g/cm² for LP in the fracture area (p = 0.078), and 0.37 g/cm² vs. 0.41 g/cm² in the distal epiphysis (p = 0.016), respectively. In conclusion, the CPT demonstrated indications of inferior stability compared to the LP in this fracture model, which may limit its clinical applicability in weight-bearing or high-load scenarios and in non-compliant patients.