Abstract
Forty-three medical centers participated in a national (United States) surveillance study of parenteral antimicrobial agents as empiric therapy of pathogens isolated from blood, skin wounds, respiratory tract, and urine (>8500 strains, 200 per laboratory). All laboratories tested each organism by the same reagent disks and/or Etest (AB Biodisk, Solna, Sweden) strips. Quality control results validated all laboratories for analyses. The most common isolates were Escherichia coli (1648), Staphylococcus aureus (1408), Pseudomonas aeruginosa (1003), Klebsiella species (792), and the enterococci (684). Among the tested drugs the percent susceptible rates observed were ofloxacin (83.4%), ciprofloxacin (82.0%), and cefuroxime (62.9%) tested against all organisms; cefazolin (54.7%) and ceftazidime (76.7%) tested against all nonfastidious aerobes; gentamicin (91.2%), imipenem (95.3%), ticarcillin-clavulanate (78.2%), and ceftriaxone (66.2%) rested against Gram-negative organisms only; and vancomycin (97.9%) and erythromycin (49.2%) tested against Gram-positive aerobes. Several drug-resistant species appear to be emerging or increasing in the United States: (a) vancomycin-resistant enterococci (7.9%, mostly Enterococcus faecium); (b) oxacillin-resistant S. aureus (21.0%); (c) third-generation cephalosporin-resistant Enterobacteriaceae, including E. coli and Klebsiella species with extended-spectrum beta-lactamases (approximately 1.3%-8.6%); (d) penicillin-resistant Streptococcus pneumoniae (17.8%); and (e) ciprofloxacin-resistant P. aeruginosa (14.9%). Fluoroquinolone resistance among the enteric bacilli was confirmed in 60 of 66 referred strains (0.8% of total strains), and cross-resistance was high among ciprofloxacin, ofloxacin, lomefloxacin, fleroxacin, and norfloxacin (98.3%-100%), Seventeen strains of fluoroquinolone-resistant enteric bacilli (0.2% of total) also harbored an ESBL and resistance to aminoglycosides. Clonal spread within medical centers was observed with the ESBL-producing Klebsiella pneumoniae. This national clinical isolate data base continues to demonstrate broad fluoroquinolone efficacy (ofloxacin > ciprofloxacin) against hospital-based pathogens and many strains of emerging resistant bacteria. Continued US surveillance studies are urged to monitor emerging antimicrobial resistance and to guide interventions to minimize its occurrence.