Antimicrobial resistance (AMR) in bacteria has clinical and public health significance. This Canadian study determined prevalence of AMR in the common mastitis pathogens Staphylococcus aureus, including methicillin-resistant Staph. aureus (MRSA), Escherichia coli , and Klebsiella species, including extended-spectrum β-lactamase (ESBL)-producing E. coli and Klebsiella species. Milk samples were collected on 89 dairy farms in 6 Canadian provinces. 

Sensititer bovine mastitis plate (Trek Diagnostic Systems Inc., Cleveland, OH) was used to determine the minimum inhibitory concentrations and a National Antimicrobial Resistance Monitoring System gram-negative panel containing antimicrobials was used for mastitis treatment and control. Denim blue chromogenic agar and real-time PCR were used to screen and confirm MRSA, respectively. 

Conclusion on the study was that prevalence of AMR in bovine mastitis pathogens was low. Most gram-negative udder pathogens were multidrug resistant; MRSA was rarely found, and ESBL E. coli and Klebsiella species isolates were absent in the Canadian milk samples.

In 2010 the Danish Research Centre for Agriculture, Cattle department, established a project with Arla Foods to reduce the level of thermo-resistant cells in raw milk through increased focus on the cleaning procedures of milking equipment and bulk milk tanks on the farms. High level of thermo-resistant cells influence on the payment to the farmer and the shelf life of dairy products like cheese and some types of milk powder are reduced.

The project included all Danish dairy farmers and it has been a great success, so in only two years the average thermo-resistant cell count has been reduced from 2084 cells in 2010 to only 598 in 2012..