Ampicillin-resistant enterococcal species in an acute-care hospital

Abstract

A prospective review of all enterococcal isolates for 13 months showed that 9.0% were resistant to ampicillin (MIC, greater than or equal to 16 micrograms/ml; zone diameter, less than 15 mm), as determined by the Vitek system, disk diffusion, microdilution MIC testing, and macrodilution MIC testing. All were beta-lactamase negative. A total of 19 and 3 resistant isolates were from urine and intravascular sites, respectively. Ampicillin-resistant enterococci appear to be a growing clinical problem.