High-pressure liquid chromatographic method for analysis of cephalosporins

Hospital routine analysis of penicillins, third-generation cephalosporins and aztreonam by conventional and high-speed high-performance liquid chromatography

A high-performance liquid chromatographic procedure for the measurement of fifteen beta-lactam antibiotics in body fluids is described, with special reference to high-speed techniques. The procedure involves a unique sample preparation before analysis for all the following fifteen compounds: benzylpenicillin, ampicillin, cloxacillin, ticarcillin, mezlocillin, azlocillin, piperacillin, cefotaxime and its desacetyl metabolite, cefsulodin, cefoperazone, cefmenoxime, ceftazidime, ceftriaxone and the monobactam aztreonam; thus all biological samples arriving at the laboratory can be treated in batch. Of these fifteen antibiotics, eleven can be chromatographed with the same type of mobile phase, which consists of a mixture of ammonium acetate and acetonitrile in various ratios. Three others need ionpairing chromatography because of their polarity, and ticarcillin requires citric acid. High-speed high-performance liquid chromatography seems to be particularly suitable for the routine analysis of beta-lactam antibiotics because columns equilibrate more rapidly, retention times are much shorter, detection limits are lower and the longer lifetime of columns reduces analysis costs.

Canine model for the simultaneous measurement of antibiotic levels in tissues and bacterial killing rate

Antibiotic levels in serum are commonly used to guide antibiotic therapy. The antibiotic levels in interstitial fluid are a more accurate reflection of the efficacy of antibiotic penetration into the tissues. Although there are experimental models for determining interstitial fluid levels, there is no model for measuring the in vivo killing of bacteria, which is the endpoint of antibiotic therapy. We developed an accurate, reliable animal model which allows measurement of the in vivo killing of bacteria along with a determination of antibiotic levels in tissues. Modified Sykes-Moore chambers were applied to the dissected external oblique muscle of 14 dogs. The chambers were inoculated with clinical isolates of Staphylococcus aureus or Escherichia coli. The dogs were treated with cefoxitin or gentamicin. Quantitative cultures were performed, and the antibiotic levels in interstitial fluid were determined.