In vitro activity of fourth generation cephalosporins against enterobacteriaceae producing extended-spectrum beta-lactamases.

The in vitro activity of fourth generation cephalosporins against Enterobacteriaceae that produce extended-spectrum beta-lactamases (ESBLs) has not been extensively studied. From an examination of the data available in the published literature and from studies performed in the author's laboratory, several trends are apparent. Introduction of any ESBL into Escherichia coli significantly reduces activity. The precise impact of an ESBL on activity varies greatly with the specific ESBL present. Derivatives of SHV-1 tend to decrease activity more than derivatives of TEM-1 or TEM-2 although there is great variation within both of the major types of ESBLs. Activity of fourth generation cephalosporins against clinical isolates of ESBL-producing Enterobacteriaceae is significantly greater than that of ceftazidime. However, cefotaxime shows activity similar to that of fourth generation cephalosporins against certain strains. The value of fourth generation cephalosporins in treating infections due to ESBL-producing Enterobacteriaceae is currently unknown as there are no clinical data available that address this issue.