Enzymatic method for rapid and sensitive determination of beta-lactam antibiotics

A rapid and sensitive procedure for the estimation of beta-lactam antibiotics is described which makes use of the ability of these antibiotics to inactivate the R39 DD-carboxypeptidase. Depending on the values of the kinetic parameters which govern the reaction, the antibiotics fall into two groups. The lower limit for the quantitative estimation of the antibiotics of groups I and II is about 5 and 50 pmol/ml, respectively. The procedure has been adopted to biological fluids such as human sera and cows' milk.