PREVALENCE OF IMPORTANT PATHOGENS AND ANTIMICROBIAL ACTIVITY OF PARENTERAL DRUGS AT NUMEROUS MEDICAL-CENTERS IN THE UNITED-STATES .1. STUDYON THE THREAT OF EMERGING RESISTANCES - REAL OR PERCEIVED

Forty-three medical centers participated in a national (United States) surveillance study of parenteral antimicrobial agents as empiric ther apy 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, Sol na, Sweden) strips. Quality control results validated all laboratories for analyses. The most common isolates were Escherichia coil (1648), Staphylococcus aureus (1408), Pseudomonas aeruginosa (1003), Klebsiell a species (792), and the enterococci (684). Among the tested drugs the percent susceptible rates observed were ofloxacin (83.4%), ciprofloxa cin (82.0%), and cefuroxime (62.9%) tested against all organisms; cefa zolin (54.7%) and ceftazidime (76.7%) tested against all nonfastidious aerobes; gentamicin (91.2%), imipenem (95.3%), ticarcillin-clavulanat e (78.2%), and ceftriaxone (66.2%) rested against Gram-negative organi sms only; and vancomycin (97.9%) and erythromycin (49.2%) tested again st 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-resista nt S. aureus (21.0%); (c) third-generation cephalosporin-resistant Ent erobacteriaceae, including E. coli and Klebsiella species with extende d-spectrum beta-lactamases (approximately 1.3%-8.6%); (d) penicillin-r esistant Streptococcus pneumoniae (17.8%); and (e) ciprofloxacin-resis tant P. aeruginosa (14.9%). Fluoroquinolone resistance among the enter ic bacilli was confirmed in 60 of 66 referred strains (0.8% of total s trains), and cross-resistance was high among ciprofloxacin, ofloxacin, lomefloxacin, fleroxacin, and norfloxacin (98.3%-100%), Seventeen str ains of fluoroquinolone-resistant enteric bacilli (0.2% of total) also harbored an ESBL and resistance to aminoglycosides. Clonal spread wit hin medical centers was observed with the ESBL-producing Klebsiella pn eumoniae. This national clinical isolate data base continues to demons trate broad fluoroquinolone efficacy (ofloxacin > ciprofloxacin) again st hospital-based pathogens and many strains of emerging resistant bac teria. Continued US surveillance studies are urged to monitor emerging antimicrobial resistance and to guide interventions to minimize its o ccurrence.