title: Relative substrate affinity index values: a method for identification of beta-lactamase enzymes and prediction of successful beta-lactam therapy.
abstract: Using a nitrocefin competition assay, I determined the relative substrate affinity index (RSAI) values of nine clinically significant beta-lactamase enzymes against a range of beta-lactams. Using selected beta-lactam substrates, I observed large differences in the RSAI values of the nine enzymes that were sufficient in many cases to positively identify specific enzymes. I made use of the unique RSAI values of SHV-1, TEM-1, and TEM-2 beta lactamases with cefoxitin to screen for the presence of these enzymes in Klebsiella aerogenes clinical isolates. The RSAI values also allow for the prediction of the outcome of beta-lactam therapy against specific beta-lactamase-producing isolates.
mesh_terms: D000900:Anti-Bacterial Agents / Q000037:antagonists & inhibitors*; D002440:Cefoxitin / Q000037:antagonists & inhibitors; D002511:Cephalosporins / Q000037:antagonists & inhibitors; D004754:Enterobacter / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D007711:Klebsiella pneumoniae / Q000201:enzymology; D008826:Microbial Sensitivity Tests; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000032:analysis* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002440:Cefoxitin; D001618:beta-Lactamases; C021720:nitrocefin