Antimicrobial resistance among pathogenic bacteria from mink (Neovison vison) in Denmark

Abstract

Background: 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.

Results: 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.

Conclusions: 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.

Keywords: Antimicrobial consumption; Antimicrobial resistance; Escherichia coli; Mink; Neovison vison; Pseudomonas aeruginosa; Staphylococcus delphini; Streptococcus canis.

Fig. 1

Antimicrobial prescriptions in Danish mink production (2007–2016). The prescription of antimicrobials given in kg active compound and DADD per year, and the curve indicating number of breeding females (in millions). DADD: defined animal daily dose is the assumed average maintenance dose needed to treat one kg animal

Fig. 2

Antimicrobial prescriptions in the Danish mink production (2007–2016) by antimicrobial class. DADD defined animal daily dose is the assumed average maintenance dose needed to treat one kg animal. Others: Pleuromutilins, amphenicols, aminoglycosides, cephalosporins, colistin, fluoroquinolones, penicillin. TMP + sulphonamide: trimethoprim with sulphonamide

Fig. 3

Seasonal patterns in antimicrobial prescriptions by antimicrobial class in the Danish mink production (2007–2016). a The graph is a monthly average from the time period 2007–2016, and illustrates the seasonal pattern in antimicrobial consumption. DADD defined animal daily dose is the assumed average maintenance dose needed to treat one kg animal. b The graph is a monthly average from the time period 2007–2016, and illustrates the seasonal pattern in antimicrobial consumption relative to the size of Danish mink production (monthly average, 2007–2016). DADD/(1000 kg – biomass * day) = number of DADD’s used within a given period per tonnes live biomass multiplied by number of days at risk within the time period (month), the unit describes the prescribed antimicrobials relative to the biomass on the farm, i.e. the decrease during autumn as the kits grow and the biomass increases. Others: Pleuromutilins, amphenicols, aminoglycosides, cephalosporins, colistin, fluoroquinolones, penicillin. TMP + sulpha: trimethoprim with sulphonamide