The doripenem MICs at which 90% of the tested strains were inhibited ranged from 0.03 to 1 g/ml for 10 species of Enterobacteriaceae (n ‫؍‬ 351), from 0.03 to 0.12 g/ml for oxacillin-susceptible staphylococci (n ‫؍‬ 119), from 4 to 32 g/ml for oxacillin-resistant staphylococci (n ‫؍‬ 64), from <0.008 to 0.06 g/ml for penicillin-susceptible streptococci (n ‫؍‬ 132), and from 1 to 4 g/ml for penicillin-resistant streptococci (n ‫؍‬ 51). Overall, doripenem demonstrated in vitro activity similar to that of meropenem against gram-negative pathogens and to that of imipenem against gram-positive pathogens.

With the exception of a few localized reports, resistance to moxifloxacin and other new fluoroquinolones in common respiratory pathogens is a rare occurrence, despite significant resistance to other compound classes. Surveillance will play a key role in tracking changes in fluoroquinolone susceptibility in European countries.

A 2000-2001 U.S. Haemophilus influenzae surveillance study (n ‫؍‬ 1,434) detected nine (0.6%) ␤-lactamasenegative and ampicillin-resistant (BLNAR) isolates collected from two different hospitals. The MICs of ampicillin for all nine isolates were 4 g/ml, with results being reproducible; and all nine isolates were susceptible to amoxicillin-clavulanate, cefuroxime, cefprozil, macrolides, and fluoroquinolones. Pulsed-field gel electrophoresis of genomic DNA following SmaI digestion demonstrated identical patterns for each of the nine isolates, suggesting intra-and interhospital dissemination of a BLNAR clone.

The activity of daptomycin was assessed by using 6,973 gram-positive bacteria isolated at 50 United States hospitals in 2000 and 2001. Among the isolates of Streptococcus pneumoniae (n ‫؍‬ 1,163) collected, the rate of penicillin resistance was 16.1%; rates of oxacillin resistance among Staphylococcus aureus isolates (n ‫؍‬ 1,018) and vancomycin resistance among Enterococcus faecium isolates (n ‫؍‬ 368) were 30.0 and 59.5%, respectively. Multidrug-resistant (MDR) phenotypes (isolates resistant to three or more different chemical classes of antimicrobial agents) accounted for 14.2% of S. pneumoniae isolates, 27.1% of S. aureus isolates, and 58.4% of E. faecium isolates. For all gram-positive species tested, MICs at which 90% of the isolates tested were inhibited (MIC 90 s) and MIC ranges for directed-spectrum agents (daptomycin, quinupristin-dalfopristin, and linezolid) were identical or highly similar for isolates susceptible or resistant to other agents or MDR. Daptomycin had a MIC 90 of 0.12 g/ml for both penicillin-susceptible and -resistant isolates of S. pneumoniae. Against oxacillin-resistant S. aureus daptomycin had a MIC 90 of 0.5 g/ml, and it had a MIC 90 of 4 g/ml against both vancomycin-susceptible and -resistant E. faecium. The MIC 90 s for daptomycin and other directed-spectrum agents were unaffected by the regional or anatomical origin of isolates or patient demographic parameters (patient age, gender, and inpatient or outpatient care). Our results confirm the gram-positive spectrum of activity of daptomycin and that its activity is independent of susceptibility or resistance to commonly prescribed and tested antimicrobial agents. This study may serve as a baseline to monitor future changes in the susceptibility of gram-positive species to daptomycin following its introduction into clinical use.

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