Antimicrobial resistance in key bloodstream bacterial isolates: Electronicsurveillance with The Surveillance Network Database - USA

To assess the prevalence of antimicrobial-resistant pathogens among the mos t common bloodstream isolates, we examined antimicrobial susceptibility dat a from The Surveillance Network Database-USA, an electronic surveillance sy stem that collects data from 118 clinical microbiology laboratories across the United States. Between 1995 and 1997, resistance to both vancomycin and ampicillin was much more prevalent among Enterococcus faecium than Enteroc occus faecalis, suggesting the need for laboratories to identify to species . When staphylococcal isolates were examined for reduced susceptibility to vancomycin (minimum inhibitory concentration = 4 mu g/mL), the frequency wa s highest in methicillin-resistant coagulase-negative staphylococci. We als o learned that nonsusceptibility to ceftazidime in Klebsiella pneumoniae wa s more prevalent among isolates from blood (12.7%) than among isolates from urine (7.1%) or respiratory sources (9.3%). Although antimicrobial resista nce is low overall for isolates of Escherichia coli from blood, the prevale nce of cefoxitin resistance among ceftazidime-resistant strains (61.9%) sug gests the action of mechanisms other than extended-spectrum beta-lactamase.