Tuesday, 13 June 2017

Novel antibiotic resistance gene in milk

A new antibiotic resistance gene has been found in bacteria from dairy cows. This gene confers resistance to all beta-lactam antibiotics including the last generation of cephalosporins used against methicillin-resistant Staphylococcus aureus. A transfer to S. aureus which is likely according to the researchers would jeopardize the use of reserve antibiotics to treat human infections caused by multidrug-resistant bacteria in hospitals.

Macrococcus caseolyticus is a harmless bacterium naturally found on the skin of dairy cows which can spread to milk during the milking process. It can also be present in dairy products made from raw milk like e.g. cheese. Researchers of the Institute of Veterinary Bacteriology of the University of Bern have identified a new methicillin resistance gene in strains of M. caseolyticus isolated from milk. Transfer of the gene to Staphylococcus aureus, a bacterium found on the skin and mucosa of animals and humans, would have dramatic consequences for public health. This methicillin resistance gene would turn this bacteria into a hazardous methicillin-resistant S. aureus (MRSA), which is known to cause difficult-to-treat infections in hospitals. Acquired methicillin resistance in bacteria is associated with genes mecA, mecB, or mecC. However, none of these genes were present in the M. caseolyticus strains -- they carried the novel resistance gene mecD.


Sybille Schwendener, Kerstin Cotting, Vincent Perreten. Novel methicillin resistance gene mecD in clinical Macrococcus caseolyticus strains from bovine and canine sources. Scientific Reports, 2017; 7: 43797 DOI: 10.1038/srep43797

Posted by Dr. Tim Sandle