EDGE (KB-56-001-007, KB-37-003-064)

Dry cow therapy before calving in pregnant dairy cows is regularly used with the narrow-spectrum semi-synthetic beta-lactam antibiotic cloxacillin. This therapy reduces the risk of chronic mastitis caused by Gram-positive cocci (streptococci and staphylococci) after calving and is responsible for a large share of the total use of antibiotics in this sector. Although this drug is not effective against infections of E. coli and other Gram-negative bacteria, there are indications that this drug still causes a certain degree of growth inhibition in these bacteria. This project will investigate to what extent cloxacillin occurs in the colostrum of dairy cows and whether these residues may have a selective effect on ESBL-producing E. coli in vitro, compared to beta-lactam sensitive E. coli. In addition, various ESBL enzymes are purified to compare the hydrolysis of cloxacillin with other beta-lactam antibiotics.