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In Vitro Susceptibility of Mastitis Pathogens Isolated from Clinical Mastitis Cases on Northern German Dairy Farms

1
Department of Microbiology, University of Applied Sciences and Arts, D-30453 Hannover, Germany
2
Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1870 Frederiksberg C, Denmark
*
Author to whom correspondence should be addressed.
Vet. Sci. 2020, 7(1), 10; https://doi.org/10.3390/vetsci7010010
Received: 25 December 2019 / Revised: 13 January 2020 / Accepted: 15 January 2020 / Published: 20 January 2020
(This article belongs to the Section Clinical Veterinary Medicine)
The present research study investigated the susceptibility of common mastitis pathogens—obtained from clinical mastitis cases on 58 Northern German dairy farms—to routinely used antimicrobials. The broth microdilution method was used for detecting the Minimal Inhibitory Concentration (MIC) of Streptococcus agalactiae (n = 51), Streptococcus dysgalactiae (n = 54), Streptococcus uberis (n = 50), Staphylococcus aureus (n = 85), non-aureus staphylococci (n = 88), Escherichia coli (n = 54) and Klebsiella species (n = 52). Streptococci and staphylococci were tested against cefquinome, cefoperazone, cephapirin, penicillin, oxacillin, cloxacillin, amoxicillin/clavulanic acid and cefalexin/kanamycin. Besides cefquinome and amoxicillin/clavulanic acid, Gram-negative pathogens were examined for their susceptibility to marbofloxacin and sulfamethoxazole/trimethoprim. The examined S. dysgalactiae isolates exhibited the comparatively lowest MICs. S. uberis and S. agalactiae were inhibited at higher amoxicillin/clavulanic acid and cephapirin concentration levels, whereas S. uberis isolates additionally exhibited elevated cefquinome MICs. Most Gram-positive mastitis pathogens were inhibited at higher cloxacillin than oxacillin concentrations. The MICs of Gram-negative pathogens were higher than previously reported, whereby 7.4%, 5.6% and 11.1% of E. coli isolates had MICs above the highest concentrations tested for cefquinome, marbofloxacin and sulfamethoxazole/trimethoprim, respectively. Individual isolates showed MICs at comparatively higher concentrations, leading to the hypothesis that a certain amount of mastitis pathogens on German dairy farms might be resistant to frequently used antimicrobials. View Full-Text
Keywords: bovine mastitis; antimicrobial susceptibility; minimal inhibitory concentration (MIC); staphylococci; streptococci; coliforms bovine mastitis; antimicrobial susceptibility; minimal inhibitory concentration (MIC); staphylococci; streptococci; coliforms
MDPI and ACS Style

Bolte, J.; Zhang, Y.; Wente, N.; Krömker, V. In Vitro Susceptibility of Mastitis Pathogens Isolated from Clinical Mastitis Cases on Northern German Dairy Farms. Vet. Sci. 2020, 7, 10.

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