Characterization of the plasmid mediated beta-lactamase BIL-1.

A multi-resistant strain of Escherichia coli isolated from a patient from Pakistan was shown to possess a new plasmid-mediated beta-lactamase. This enzyme, designated BIL-1, conferred resistance to extended-spectrum cephalosporins such as cefotaxime and ceftazidime. However, unlike other plasmid-mediated beta-lactamases capable of conferring resistance to these drugs, the BIL-1 was not a member of the TEM or SHV group of plasmid-mediated beta-lactamases and it also conferred resistance to beta-lactam drugs in combination with beta-lactamase inhibitors (i.e. clavulanic acid). The biochemical properties of the enzyme suggest that BIL-1 is related to the Richmond & Sykes Class I chromosomal beta-lactamases. Its inhibition properties by various beta-lactam drugs are similar to the inhibition properties of the chromosomally-encoded P99 enzyme of Enterobacter cloacae.