Concurrent resistance to antimicrobials of different structural classes has arisen in a multitude of bacterial species and may complicate the therapeutic management of infections, including those of the urinary tract. To assess the current breadth of multidrug resistance among urinary isolates of Escherichia coli, the most prevalent pathogen contributing to these infections, all pertinent results in The Surveillance Network Database-USA from 1 January to 30 September 2000 were analyzed. Results were available for 38,835 urinary isolates of E. coli that had been tested against ampicillin, cephalothin, ciprofloxacin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Of these isolates, 7.1% (2,763 of 38,835) were resistant to three or more agents and considered multidrug resistant. Among the multidrug-resistant isolates, 97.8% were resistant to ampicillin, 92.8% were resistant to trimethoprim-sulfamethoxazole, 86.6% were resistant to cephalothin, 38.8% were resistant to ciprofloxacin, and 7.7% were resistant to nitrofurantoin. The predominant phenotype among multidrug-resistant isolates (57.9%; 1,600 of 2,793) included resistance to ampicillin, cephalothin, and trimethoprim-sulfamethoxazole. This was the most common phenotype regardless of patient age, gender, or inpatient-outpatient status and in eight of the nine U.S. Bureau of the Census regions. Rates of multidrug resistance were demonstrated to be higher among males (10.4%) than females (6.6%), among patients >65 years of age (8.7%) than patients <17 (6.8%) and 18 to 65 (6.1%) years of age, and among inpatients (7.6%) than outpatients (6.9%). Regionally, the rates ranged from 4.3% in the West North Central region to 9.2% in the West South Central region. Given the current prevalence of multidrug resistance among urinary tract isolates of E. coli in the United States (7.1%), continued local, regional, and national surveillance is warranted.

Current recommendations for empirical therapy for community-acquired urinary tract infection (UTI) in women hinge on knowledge of antimicrobial susceptibility patterns in the geographic region of the practitioner. We conducted a survey of antimicrobial susceptibilities of 103,223 isolates recovered from urine samples that were obtained in 1998 from female outpatients nationally and within 9 geographic regions in the United States. Resistance of Escherichia coli isolates to trimethoprim-sulfamethoxazole varied significantly according to geographic region, ranging from a high of 22% in the western United States to a low of 10% in the Northeast (P<.001). There were no clinically significant age-related differences in the susceptibility of E. coli to any of the study drugs, but the susceptibility to fluoroquinolones of non-E. coli isolates that were recovered from women who were aged >50 years was significantly lower than that of isolates recovered from younger women (P<.001). The in vitro susceptibility of uropathogens in female outpatients varies according to age and geographic region.

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.The potent activity of fluoroquinolones (FQs) against a myriad of gram-negative and gram-positive bacterial pathogens has fostered a decade of frequent and continued clinical use. Recently, levofloxacin has broadened the range of indications for FQs to include community-acquired respiratory tract infections attributable to penicillin-resistant Streptococcus pneumoniae. In spite of their success, concern remains regarding the development and increasing prevalence of resistance to FQs among human pathogens and colonizing bacterial species (12,23,24,25).A decline in the activity of FQs would be especially problematic in view of the ability of gram-negative bacilli to acquire resistance to all other classes of antimicrobials (4,5,10,11,14,15,17,20,22,29,30). This ability underscores the need to closely monitor FQ activity in the Uni...

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Publication of the NCCLS M100-S12 document in January 2002 introduced ceftriaxone and cefotaxime MIC interpretative breakpoints of <1 g/ml (susceptible), 2 g/ml (intermediate), and >4 g/ml (resistant) for nonmeningeal isolates of Streptococcus pneumoniae. To estimate the effect of these breakpoint changes on clinical laboratory susceptibility testing results, nonmeningeal pneumococcal isolate (blood and respiratory) data from The Surveillance Network Database-USA, an electronic surveillance database, for the years 1996 to 2000 were collated and studied. Of 9,863 nonmeningeal isolates tested against ceftriaxone, 82.7% were susceptible, 13.2% were intermediate, and 4.1% were resistant by the M100-S11 NCCLS breakpoints (2001); by M100-S12 breakpoints, 95.9% of the isolates were susceptible, 3.1% were intermediate, and 1.0% were resistant. Of 10,777 nonmeningeal isolates tested against cefotaxime, 79.2% were susceptible, 14.3% were intermediate, and 6.5% were resistant by M100-S11 breakpoints; by M100-S12 breakpoints, 93.5% were susceptible, 4.2% were intermediate, and 2.3% were resistant. Overall, the new M100-S12 ceftriaxone and cefotaxime interpretative breakpoints for nonmeningeal isolates of S. pneumoniae decreased the number of isolates interpreted as intermediate by 10% and as resistant by 3 to 4%.Ceftriaxone and cefotaxime MIC interpretative breakpoints for meningeal and nonmeningeal isolates of Streptococcus pneumoniae were published by the NCCLS in the M100-S12 document in January 2002 (12). Previously, a single set of MIC interpretive breakpoints (M100-S11, 2001) for both meningeal and nonmeningeal isolates was used (11). M100-S11 MIC interpretative breakpoints for ceftriaxone and cefotaxime were 0.5 g/ml (susceptible), 1 g/ml (intermediate), and 2 g/ml (resistant) (11). The M100-S12 breakpoints are 0.5 g/ml (susceptible), 1 g/ml (intermediate), and 2 g/ml (resistant) for meningeal isolates and 1 g/ml (susceptible), 2 g/ml (intermediate), and 4 g/ml (resistant) for nonmeningeal isolates for both ceftriaxone and cefotaxime (12). The M100-S12 interpretative guidelines advise laboratories to report both meningeal and nonmeningeal interpretative criteria for pneumococcal isolates recovered from body sites other than cerebrospinal fluid; isolates from cerebrospinal fluid should be reported with meningeal interpretative criteria only (12).The introduction of revised amoxicillin and amoxicillin-clavulanate breakpoints in M100-S10 (10) resulted in greater than twice the number of pneumococcal isolates being interpreted as intermediate to ceftriaxone (10.3%) than to amoxicillin (4.2%) or amoxicillin-clavulanate (4.6%) and greater than six times more isolates being interpreted as resistant to ceftriaxone (14.4%) than to amoxicillin (2.2%) or amoxicillin-clavulanate (1.7%) (4). Similarly, Oteo et al. reported 23.6% of isolates to be cefotaxime intermediate and 4.5% to be cefotaxime resistant compared with 5.6% being amoxicillin intermediate and 3.8% being amoxicillin resistant despite MICs at which 90% of the isolat...