Antimicrobial Agents and Chemotherapy, January 2001, p. 267-274, Vol. 45, No. 1
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.1.267-274.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
MRL, Herndon, Virginia 20171,1 MRL, Brentwood, Tennessee 37027,2 and Ortho-McNeil Pharmaceutical, Inc., Raritan, New Jersey 088693
Received 15 June 2000/Returned for modification 28 September 2000/Accepted 26 October 2000
Given the propensity for Enterobacteriaceae and
clinically significant nonfermentative gram-negative bacilli to acquire
antimicrobial resistance, consistent surveillance of the activities of
agents commonly prescribed to treat infections arising from these
organisms is imperative. This study determined the activities of
two fluoroquinolones, levofloxacin and ciprofloxacin, and
seven comparative agents against recent clinical isolates of
Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas
maltophilia using two surveillance strategies: 1) centralized in
vitro susceptibility testing of isolates collected from 27 hospital
laboratories across the United States and 2) analysis of data from The
Surveillance Network Database-USA, an electronic surveillance network
comprising more than 200 laboratories nationwide. Regardless of
the surveillance method, Enterobacteriaceae,
P. aeruginosa, and A. baumannii demonstrated similar rates of susceptibility to levofloxacin and ciprofloxacin. Susceptibilities to the fluoroquinolones approached or exceeded 90%
for all Enterobacteriaceae except Providencia
spp. (
65%). Approximately 70% of P. aeruginosa and 50%
of A. baumanii isolates were susceptible to
both fluoroquinolones. Among S. maltophilia isolates, 50%
more isolates were susceptible to levofloxacin than to ciprofloxacin.
Overall, the rate of ceftazidime nonsusceptibility among
Enterobacteriaceae was 8.7%, with fluoroquinolone
resistance rates notably higher among ceftazidime-nonsusceptible
isolates than ceftazidime-susceptible ones. Multidrug-resistant
isolates were present among all species tested but were most
prevalent for Klebsiella pneumoniae and
Enterobacter cloacae. No gram-negative isolates resistant
only to a fluoroquinolone were encountered, regardless of species. Thus, while levofloxacin and ciprofloxacin have
maintained potent activity against Enterobacteriaceae, the potential for fluoroquinolone resistance, the apparent association between fluoroquinolone and cephalosporin resistance, and the presence of multidrug resistance in every species examined emphasize the need to maintain active surveillance of resistance patterns among gram-negative bacilli.
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