Beta-lactamase as biochemical parameter of antibiotic resistance
Lin, J.K.; Hou, T.T.
Journal of the Formosan Medical Association 84(12): 1334-1343
1985
ISSN/ISBN: 0371-7682 PMID: 3879690 Document Number: 248278
A rapid quantitative fluorometric method was developed for the determination of microbial .beta.-lactamases which use ampicillin, cephalexin and cephadroxil as substrates. The end products (open .beta.-lactam ring forms) liberated after separately incubating either substrate with .beta.-lactamase-producing organisms were converted to highly fluorescent derivatives and extracted into methanol. The amounts of these products were then measured fluorometrically with 360 and 420 nm as excitation and emission wavelengths respectively. A simple qualitative spot test for the end-products was also described. The agar diffusion method was used to determine the diameters of inhibition zones induced by several .beta.-lactam antibiotics. The results indicated that Escherichia coli RRI and Salmonella typhimurium (TA 1535, TA1537) were sensitive to these antibiotics, but when these Gram-negative bacteria acquired their plasmids such as E. coli RRI (PBR322), they became resistant. It has been indicated that the plasmid-encoded .beta.-lactamases were responsible to this drug resistance.