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%) tested 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.