SUBSTITUTION OF ALANINE FOR ASPARTATE AT POSITION-179 IN THE SHV-6 EXTENDED-SPECTRUM BETA-LACTAMASE

SHV-6 was previously identified by its susceptibility pattern and bioc hemical criteria in a clinical isolate of Klebsiella pneumoniae which was resistant to ceftazidime. It contains only a single point differen ce with the beta la(SHV-1) gene as determined by PCR amplification and nucleotide sequencing. This is the result of a single amino acid subs titution, Ala for Asp, at position 179. Directed mutagenesis experimen ts have shown this substitution to confer selective resistance to ceft azidime in the TEM family.