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

Yanchao Zhang,Volker Krömker,Josef Bolte,Nicole Wente

doi:10.3390/vetsci7010010

Yanchao Zhang, Volker Krömker + Show 2 more

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https://doi.org/10.3390/vetsci7010010

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Journal: Veterinary sciences	Publication Date: Jan 20, 2020
Citations: 16	License type: CC BY 4.0

Affiliation: Hochschule Hannover, University of Copenhagen

Abstract

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.

Highlights

The pathogens predominantly associated with bovine mastitis in Germany are substantially staphylococci, streptococci and coliforms [1]
MIC50 and MIC90 values corresponded to the same concentration level for cefoperazone (0.25 μg/mL), oxacillin (0.5 μg/mL), amoxicillin/clavulanic acid (0.5 μg/mL) and cefalexin/kanamycin (4 μg/mL)
While cefoperazone MIC50 and MIC90 corresponded to the same concentration level (0.25 μg/mL), MIC90 values of cephapirin, cloxacillin, oxacillin, amoxicillin/clavulanic acid and cefalexin/kanamycin were at least one dilution higher than their MIC50

Summary

Introduction

The pathogens predominantly associated with bovine mastitis in Germany are substantially staphylococci, streptococci and coliforms [1]. Clinical mastitis cases are treated using antimicrobial substances that are locally applied into the teat canal subsequent to the occurrence of clinical signs. The treatment of clinical bovine mastitis with antimicrobial agents is frequently induced without prior knowledge of causative agents and preferred use of antimicrobials covering a broad spectrum of pathogens. According to unpublished data provided by the German Consumer. Research Company (GfK), udder injectors containing cephalosporins were used most frequently in the first quarter of 2017. Both cefoperazone and cefquinome, belonging to cephalosporins of the thirdand fourth-generation, achieved a total market share of 39% in Germany.

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