scholarly journals Antibiotic resistance among clinical isolates of Haemophilus influenzae in the United States in 1994 and 1995 and detection of beta-lactamase-positive strains resistant to amoxicillin-clavulanate: results of a national multicenter surveillance study.

1997 ◽  
Vol 41 (2) ◽  
pp. 292-297 ◽  
Author(s):  
G V Doern ◽  
A B Brueggemann ◽  
G Pierce ◽  
H P Holley ◽  
A Rauch
Keyword(s):  
Haemophilus Influenzae ◽  
Antimicrobial Agents ◽  
Clinical Laboratory ◽  
Rank Order ◽  
Medical Center ◽  
The United States ◽  
Clinical Isolates ◽  
National Committee ◽  
Beta Lactamase ◽  
Amoxicillin Clavulanate

A total of 1,537 clinical isolates of Haemophilus influenzae were recovered in 30 U.S. medical center laboratories between 1 November 1994 and 30 April 1995 and were characterized in a central laboratory with respect to serotype and beta-lactamase production and the in vitro activities of 15 oral antimicrobial agents. Overall, 36.4% of the isolates were found to produce beta-lactamase. The rank order of activity of six cephalosporins on the basis of MICs was cefixime > cefpodoxime > cefuroxime > loracarbef > or = cefaclor > cefprozil. On the basis of current National Committee for Clinical Laboratory Standards (NCCLS) breakpoints ages of isolates found to be resistant or intermediate to these agents were as follows: 0.1, 0.3, 6.4, 16.3, 18.3, and 29.8, respectively (National Committee for Clinical Laboratory Standards. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically, 4th ed. M7-A4, 1995). Azithromycin was, on a weight basis, the most potent of the macrolides tested in this study, followed by erythromycin and then clarithromycin. Azithromycin was typically fourfold more active than erythromycin, which was, in turn, slightly more active than clarithromycin. However, when compared on the basis of the frequency of resistance determined by using current NCCLS breakpoints, there was essentially no difference between azithromycin and clarithromycin, i.e., 0.5 and 1.9%, respectively (P = 0.086). Interpretive breakpoints for erythromycin MIC tests versus H. influenzae have not been developed. Resistance to other non- beta-lactam agents was variable, as follows: trimethoprim-sulfamethoxazole, 9.0%; chloramphenicol, 0.2%; tetracycline, 1.3%; and rifampin, 0.3%. Two conspicuous findings in this study were the identification of 39 strains H. influenzae that were beta-lactamase negative but ampicillin intermediate or resistant (BLNAR) and, even more surprisingly, 17 beta-lactamase-positive isolates that were resistant to amoxicillin-clavulanate (BLPACR). Strains of H. influenzae in the first group have heretofore been very uncommon; organisms in the second group have not previously been described in the literature. The percentages of all study isolates comprised of BLNAR and BLPACR organisms were 2.5 and 1.1, respectively. Overall resistance to ampicillin was thus 38.9%, and that to amoxicillin-clavulanate was 4.5%.

scholarly journals Prevalence of antimicrobial resistance among 723 outpatient clinical isolates of Moraxella catarrhalis in the United States in 1994 and 1995: results of a 30-center national surveillance study.

1996 ◽  
Vol 40 (12) ◽  
pp. 2884-2886 ◽  
Author(s):  
G V Doern ◽  
A B Brueggemann ◽  
G Pierce ◽  
T Hogan ◽  
H P Holley ◽  
...  
Keyword(s):  
United States ◽  
Moraxella Catarrhalis ◽  
Antimicrobial Agents ◽  
Clinical Laboratory ◽  
The United States ◽  
National Committee ◽  
Beta Lactamase ◽  
Central Laboratory ◽  
Medical Centers ◽  
Amoxicillin Clavulanate

Seven hundred twenty-three isolates of Moraxella catarrhalis obtained from outpatients with a variety of infections in 30 medical centers in the United States between 1 November 1994 and 30 April 1995 were characterized in a central laboratory. The overall rate of beta-lactamase production was 95.3%. When the National Committee for Clinical Laboratory Standards MIC interpretive breakpoints for Haemophilus influenzae were applied, percentages of strains found to be susceptible to selected oral antimicrobial agents were as follows: azithromycin, clarithromycin, and erythromycin, 100%; tetracycline and chloramphenicol, 100%; amoxicillin-clavulanate, 100%; cefixime, 99.3%; cefpodoxime, 99.0%; cefaclor, 99.4%; loracarbef, 99.0%; cefuroxime, 98.5%; cefprozil, 94.3%; and trimethoprim-sulfamethoxazole, 93.5%.

scholarly journals Antimicrobial resistance of Streptococcus pneumoniae recovered from outpatients in the United States during the winter months of 1994 to 1995: results of a 30-center national surveillance study.

1996 ◽  
Vol 40 (5) ◽  
pp. 1208-1213 ◽  
Author(s):  
G V Doern ◽  
A Brueggemann ◽  
H P Holley ◽  
A M Rauch
Keyword(s):  
Streptococcus Pneumoniae ◽  
Antimicrobial Agents ◽  
Clinical Laboratory ◽  
Rank Order ◽  
The United States ◽  
Penicillin Resistance ◽  
National Committee ◽  
Medical Centers ◽  
Resistant Strains ◽  
High Level

A total of 1,527 clinically significant outpatient isolates of Streptococcus pneumoniae were prospectively collected in 30 different U.S. medical centers between November 1994 and April 1995. Overall, 23.6% of strains were not susceptible to penicillin, with 14.1% intermediate and 9.5% high-level resistant. The frequencies of recovery of intermediate and high-level resistant strains varied considerably between different medical centers and in different geographic areas. In general, intermediate and high-level penicillin resistance was most common with isolates of S. pneumoniae recovered from pediatric patients. The in vitro activities of 22 other antimicrobial agents were assessed against this collection of isolates. Ampicillin was consistently 1 twofold dilution less active than penicillin. Amoxicillin and amoxicillin-clavulanate were essentially equivalent to penicillin in activity. The rank order of activity for cephalosporins was cefotaxime = ceftriaxone > or = cefpodoxime > or = cefuroxime > cefprozil > or = cefixime > cefaclor = loracarbef > cefadroxil = cephalexin. The National Committee for Clinical Laboratory Standards [Performance Standards for Antimicrobial Susceptibility Testing, Sixth Information Supplement (M100-S6), 1995] has established MIC breakpoints for resistance (i.e., > or = 2 micrograms/ml) with three cephalosporins versus S. pneumoniae, namely, cefotaxime, ceftriaxone, and cefuroxime. The overall percentages of strains resistant to these three antimicrobial agents were 3, 5, and 12, respectively. The overall frequency of resistance was 10% with all three macrolides examined in this study, clarithromycin, erythromycin, and azithromycin. The overall percentages of chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole resistance were 4.3, 7.5, and 18, respectively. The resistance percentages among the cephalosporins, macrolides, chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole were consistently higher among penicillin-intermediate strains than among susceptible isolates and even higher still among organisms expressing high-level penicillin resistance. Multiply resistant strains represented 9.1% of the organisms examined in this study. Finally, rifampin resistance was uncommon (i.e., 0.5%), and vancomycin resistance was not detected. The quinopristin-dalfopristin combination was consistently active at concentrations of 0.25 to 4 micrograms/ml, but rates of resistance could not be determined in the absence of established interpretive criteria for MIC results.

Assessment of Laboratory Performance With Streptococcus pneumoniae Antimicrobial Susceptibility Testing in the United States

1999 ◽  
Vol 123 (4) ◽  
pp. 285-289 ◽  
Author(s):  
Gary V. Doern ◽  
Angela B. Brueggemann ◽  
Michael A. Pfaller ◽  
Ronald N. Jones
Keyword(s):  
United States ◽  
Streptococcus Pneumoniae ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
The United States ◽  
National Committee ◽  
In Vitro Susceptibility ◽  
Susceptibility Tests

Abstract Objective.—To assess the performance of clinical microbiology laboratories in the United States when conducting in vitro susceptibility tests with Streptococcus pneumoniae. Methods.—The results of a nationwide College of American Pathologists Proficiency Survey test sample, in which susceptibility testing of an isolate of S pneumoniae was performed, were assessed with respect to precision and accuracy. Results.—Wide variability was noted among participating laboratories with both minimum inhibitory concentration procedures and disk diffusion susceptibility tests when both methods were applied to S pneumoniae. Despite this high degree of variation, categorical interpretive errors were uncommon. Numerous laboratories reported results for antimicrobial agents that are not recommended by the National Committee for Clinical Laboratory Standards for tests with S pneumoniae. Conclusions.—Current susceptibility testing practices with S pneumoniae in the United States indicate limited precision and a tendency for laboratories to test and report results obtained with antimicrobial agents of questionable therapeutic value against this organism. Continued efforts to standardize susceptibility testing of S pneumoniae in the United States are warranted. In addition, modifications of existing interpretive criteria may be necessary.

scholarly journals Evaluation of the Dade MicroScan MICroSTREP Antimicrobial Susceptibility Testing Panel with Selected Streptococcus pneumoniae Challenge Strains and Recent Clinical Isolates

1998 ◽  
Vol 36 (3) ◽  
pp. 788-791 ◽  
Author(s):  
J. H. Jorgensen ◽  
M. L. McElmeel ◽  
S. A. Crawford
Keyword(s):  
Streptococcus Pneumoniae ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Reference Panel ◽  
Clinical Isolates ◽  
National Committee ◽  
Broth Microdilution ◽  
Drug Concentrations ◽  
Broth Microdilution Method

The MicroScan MICroSTREP panel is a recently marketed frozen broth microdilution panel for susceptibility testing of various streptococci, including Streptococcus pneumoniae. The panel contains 10 antimicrobial agents in cation-adjusted Mueller-Hinton broth supplemented with 3% lysed horse blood, similar in concept to the National Committee for Clinical Laboratory Standards (NCCLS) reference broth microdilution method for testing streptococci. A group of 210 isolates of S. pneumoniae were selected to include isolates with previously documented resistance to agents incorporated in the MICroSTREP panel, as well as recent invasive clinical isolates. All isolates were tested simultaneously with the MICroSTREP panel and an NCCLS reference panel whose drug concentrations were prepared to coincide with those of the MICroSTREP panel. Of the 210 isolates, 5 failed to grow in the MICroSTREP panel; 3 of those also did not grow in the reference panel. Essential agreement of MICs determined by the two methods (test MIC ± one dilution of the reference MIC) was 99.6% overall and ranged from 98.0% with chloramphenicol to 100% with penicillin, ceftriaxone, erythromycin, tetracycline, and vancomycin. There were no very major or major interpretive category errors resulting from the MICroSTREP panel tests. Minor interpretive category errors ranged from 12.2% with cefotaxime and 9.8% with ceftriaxone (due mainly to clustering of MICs for the selected strains near the breakpoints) to 0% with chloramphenicol and vancomycin. These results indicate that the MicroScan MICroSTREP frozen panels provide susceptibility results with pneumococci that are essentially equivalent to results derived by the NCCLS reference broth microdilution procedure.

scholarly journals Antimicrobial Resistance among Clinical Isolates ofStreptococcus pneumoniae in the United States during 1999–2000, Including a Comparison of Resistance Rates since 1994–1995

2001 ◽  
Vol 45 (6) ◽  
pp. 1721-1729 ◽  
Author(s):  
Gary V. Doern ◽  
Kristopher P. Heilmann ◽  
Holly K. Huynh ◽  
Paul R. Rhomberg ◽  
Stacy L. Coffman ◽  
...  
Keyword(s):  
United States ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Rank Order ◽  
The United States ◽  
Clinical Isolates ◽  
Beta Lactam ◽  
High Level ◽  
Resistance Rates

ABSTRACT A total of 1,531 recent clinical isolates of Streptococcus pneumoniae were collected from 33 medical centers nationwide during the winter of 1999–2000 and characterized at a central laboratory. Of these isolates, 34.2% were penicillin nonsusceptible (MIC ≥ 0.12 μg/ml) and 21.5% were high-level resistant (MIC ≥ 2 μg/ml). MICs to all beta-lactam antimicrobials increased as penicillin MICs increased. Resistance rates among non-beta-lactam agents were the following: macrolides, 25.2 to 25.7%; clindamycin, 8.9%; tetracycline, 16.3%; chloramphenicol, 8.3%; and trimethoprim-sulfamethoxazole (TMP-SMX), 30.3%. Resistance to non-beta-lactam agents was higher among penicillin-resistant strains than penicillin-susceptible strains; 22.4% of S. pneumoniae were multiresistant. Resistance to vancomycin and quinupristin-dalfopristin was not detected. Resistance to rifampin was 0.1%. Testing of seven fluoroquinolones resulted in the following rank order of in vitro activity: gemifloxacin > sitafloxacin > moxifloxacin > gatifloxacin > levofloxacin = ciprofloxacin > ofloxacin. For 1.4% of strains, ciprofloxacin MICs were ≥4 μg/ml. The MIC90s (MICs at which 90% of isolates were inhibited) of two ketolides were 0.06 μg/ml (ABT773) and 0.12 μg/ml (telithromycin). The MIC90 of linezolid was 2 μg/ml. Overall, antimicrobial resistance was highest among middle ear fluid and sinus isolates of S. pneumoniae; lowest resistance rates were noted with isolates from cerebrospinal fluid and blood. Resistant isolates were most often recovered from children 0 to 5 years of age and from patients in the southeastern United States. This study represents a continuation of two previous national studies, one in 1994–1995 and the other in 1997–1998. Resistance rates with S. pneumoniae have increased markedly in the United States during the past 5 years. Increases in resistance from 1994–1995 to 1999–2000 for selected antimicrobial agents were as follows: penicillin, 10.6%; erythromycin, 16.1%; tetracycline, 9.0%; TMP-SMX, 9.1%; and chloramphenicol, 4.0%, the increase in multiresistance was 13.3%. Despite awareness and prevention efforts, antimicrobial resistance with S. pneumoniae continues to increase in the United States.

scholarly journals Vancomycin-Resistant Staphylococcus aureus Isolate from a Patient in Pennsylvania

2004 ◽  
Vol 48 (1) ◽  
pp. 275-280 ◽  
Author(s):  
Fred C. Tenover ◽  
Linda M. Weigel ◽  
Peter C. Appelbaum ◽  
Linda K. McDougal ◽  
Jasmine Chaitram ◽  
...  
Keyword(s):  
United States ◽  
Staphylococcus Aureus ◽  
Antimicrobial Agents ◽  
Clinical Laboratory ◽  
Pcr Amplification ◽  
The United States ◽  
Pfge Type ◽  
National Committee ◽  
Biochemical Tests ◽  
Vancomycin Resistant

ABSTRACT A vancomycin-resistant Staphylococcus aureus (VRSA) isolate was obtained from a patient in Pennsylvania in September 2002. Species identification was confirmed by standard biochemical tests and analysis of 16S ribosomal DNA, gyrA, and gyrB sequences; all of the results were consistent with the S. aureus identification. The MICs of a variety of antimicrobial agents were determined by broth microdilution and macrodilution methods following National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The isolate was resistant to vancomycin (MIC = 32 μg/ml), aminoglycosides, β-lactams, fluoroquinolones, macrolides, and tetracycline, but it was susceptible to linezolid, minocycline, quinupristin-dalfopristin, rifampin, teicoplanin, and trimethoprim-sulfamethoxazole. The isolate, which was originally detected by using disk diffusion and a vancomycin agar screen plate, was vancomycin susceptible by automated susceptibility testing methods. Pulsed-field gel electrophoresis (PFGE) of SmaI-digested genomic DNA indicated that the isolate belonged to the USA100 lineage (also known as the New York/Japan clone), the most common staphylococcal PFGE type found in hospitals in the United States. The VRSA isolate contained two plasmids of 120 and 4 kb and was positive for mecA and vanA by PCR amplification. The vanA sequence was identical to the vanA sequence present in Tn1546. A DNA probe for vanA hybridized to the 120-kb plasmid. This is the second VRSA isolate reported in the United States.

scholarly journals A Cross-Canada Surveillance of Antimicrobial Resistance in Respiratory Tract Pathogens

1999 ◽  
Vol 10 (2) ◽  
pp. 128-133 ◽  
Author(s):  
Ross J Davidson ◽  
Canadian Bacterial Surveillance Network ◽  
Donald E Low
Keyword(s):  
Antimicrobial Resistance ◽  
Clinical Laboratory ◽  
Clinical Isolates ◽  
National Committee ◽  
Beta Lactamase ◽  
Beta Lactam ◽  
Minimal Inhibitory Concentrations ◽  
Beta Lactam Antibiotics ◽  
Significant Difference ◽  
High Level

OBJECTIVE: To determine the prevalence of antimicrobial resistance in clinical isolates ofStreptococcus pneumoniae, Haemophilus influenzaeandMoraxella catarrhalisfrom medical centres across Canada.METHODS: Fifty laboratories from across Canada were asked to collect up to 25 consecutive clinical isolates ofS pneumoniae,H influenzaeandM catarrhalisat some time between September 1994 and May 1995, and then again between September and December of 1996. A total of 2364S pneumoniae, 575H influenzaeand 200M catarrhalissamples were collected.H influenzaeandM catarrhalisisolates were tested for the production of beta-lactamase.S pneumoniaeisolates were characterized as penicillin susceptible, intermediately resistant or high level penicillin-resistant. Minimal inhibitory concentrations (MICs) were determined using a microbroth dilution technique described by the National Committee of Clinical Laboratory Standards.RESULTS: Between the two collection periods, there was a significant increase in highly penicillin-resistantS pneumoniaefrom 2.1% to 4.4% (P<0.05) and an increase in intermediately penicillin-resistant strains from 6.4% to 8.9% (P<0.05). A significant increase in high level penicillin-resistantS pneumoniaewas noted among paediatric isolates. No significant difference in the susceptibilities of comparator agents was detected. A significant increase in the number of beta-lactamase producingH influenzae, 34% to 43% (P<0.05) was observed. Ninety-five per cent ofM catarrhalisisolates were beta-lactamase producers in both time periods.CONCLUSIONS: During the course of this study, the incidence of penicillin resistance inS pneumoniaedoubled. As a result of this increase, infections due to this organism in sites where poor penetration of beta-lactam antibiotics occur may become increasingly difficult to manage.

scholarly journals In Vitro Susceptibilities of CandidaBloodstream Isolates to the New Triazole Antifungal Agents BMS-207147, Sch 56592, and Voriconazole

1998 ◽  
Vol 42 (12) ◽  
pp. 3242-3244 ◽  
Author(s):  
M. A. Pfaller ◽  
S. A. Messer ◽  
R. J. Hollis ◽  
R. N. Jones ◽  
G. V. Doern ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Clinical Laboratory ◽  
Rank Order ◽  
The United States ◽  
Antifungal Drugs ◽  
National Committee ◽  
Clinical Value ◽  
Medical Centers

ABSTRACT BMS-207147, Sch 56592, and voriconazole are three new investigational triazoles with broad-spectrum antifungal activity. The in vitro activities of these three agents were compared with those of itraconazole and fluconazole against 1,300 bloodstream isolates ofCandida species obtained from over 50 different medical centers in the United States. The MICs of all of the antifungal drugs were determined by broth microdilution tests performed according to the National Committee for Clinical Laboratory Standards method using RPMI 1640 as a test medium. BMS-207147, Sch 56592, and voriconazole were all quite active against all Candida sp. isolates (MICs for 90% of the isolates tested [MIC90s], 0.5, 1.0, and 0.5 μg/ml, respectively). Candida albicans was the most susceptible species (MIC90s, 0.03, 0.06, and 0.06 μg/ml, respectively), and C. glabrata was the least susceptible (MIC90s, 4.0, 4.0, and 2.0 μg/ml, respectively). BMS-207147, Sch 56592, and voriconazole were all more active than itraconazole and fluconazole against C. albicans, C. parapsilosis, C. tropicalis, and C. krusei. There existed a clear rank order of in vitro activity of the five azoles examined in this study when they were tested versusC. glabrata: voriconazole > BMS-207147 = Sch 56592 = itraconazole > fluconazole (MIC90s, 2.0, 4.0, 4.0, 4.0, and 64 μg/ml, respectively). For isolates ofCandida spp. with decreased susceptibility to both itraconazole and fluconazole, the MICs of BMS-207147, Sch 56592, and voriconazole were also elevated. These results suggest that BMS-207147, Sch 56592, and voriconazole all possess promising antifungal activity and that further in vitro and in vivo investigations are warranted to establish the clinical value of this improved potency.

Imipenem/relebactam activity compared to other antimicrobials against non-MBL-producing carbapenem-resistant Enterobacteriaceae from an academic medical center

2019 ◽  
Vol 77 (4) ◽  
Author(s):  
Brandon Kulengowski ◽  
David S Burgess
Keyword(s):  
Antimicrobial Agents ◽  
Medical Center ◽  
Phenylboronic Acid ◽  
Academic Medical Center ◽  
Clinical Isolates ◽  
Beta Lactamase ◽  
In Vitro Susceptibility ◽  
Carbapenem Resistant ◽  
Academic Medical ◽  
Carbapenem Resistant Enterobacteriaceae

ABSTRACTBackgroundCarbapenem-resistant Enterobacteriaceae (CRE) cause significant mortality and are resistant to most antimicrobial agents. Imipenem/relebactam, a novel beta-lactam/beta-lactamase inhibitor combination, and 16 other antimicrobials were evaluated against non-metallo-beta-lactamase-producing carbapenem-resistant Enterobacteriaceae clinical isolates from a United States tertiary academic medical center.ObjectivesTo evaluate imipenem/relebactam and other commonly utilised antimicrobial agents against carbapenem-resistant Enterobacteriaceae. Methods: Clinical isolates (n  = 96) resistant to ertapenem or meropenem by BD Phoenix (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) and negative for metallo-beta-lactamase-production by an EDTA (Sigma-Aldrich Corp., St. Louis, MO, USA)/phenylboronic acid (Sigma-Aldrich Corp., St. Louis, MO, USA) disk diffusion assay were identified and collected from January 2012 to January 2017. In vitro susceptibility by broth microdilution was performed according to CLSI guidelines using CLSI susceptibility breakpoints for 17 antimicrobials (Sigma-Aldrich Corp., St. Louis, MO, USA).ResultsCRE primarily produced Klebsiella pneumoniae carbapenemase (KPC) and consisted primarily of K. pneumoniae (55%) and Enterobacter spp. (25%), followed by Citrobacter spp. (10%), Escherichia coli (5%), and others (5%). CRE were most susceptible to imipenem/relebactam (100%), followed by amikacin (85%), tigecycline (82%), and polymyxin B/colistin (65%). The median reduction of imipenem minimum inhibitory concentrations (MICs) of non-MBL-producing CRE was 16-fold but ranged from 0.5 to >512-fold. The MIC50, MIC90 and MIC range of imipenem/relebactam was 0.5/4, 1/4 and 0.06/4–1/4 mg/L, respectively.ConclusionsImipenem/relebactam exhibits excellent activity against CRE that produce KPC.

scholarly journals Antifungal Activities of Posaconazole, Ravuconazole, and Voriconazole Compared to Those of Itraconazole and Amphotericin B against 239 Clinical Isolates of Aspergillus spp. and Other Filamentous Fungi: Report from SENTRY Antimicrobial Surveillance Program, 2000

2002 ◽  
Vol 46 (4) ◽  
pp. 1032-1037 ◽  
Author(s):  
M. A. Pfaller ◽  
S. A. Messer ◽  
R. J. Hollis ◽  
R. N. Jones
Keyword(s):  
Amphotericin B ◽  
Filamentous Fungi ◽  
Antifungal Agents ◽  
Clinical Laboratory ◽  
The United States ◽  
Clinical Isolates ◽  
National Committee ◽  
Surveillance Program ◽  
In Vitro Susceptibility

ABSTRACT Posaconazole, ravuconazole, and voriconazole are new triazole derivatives that possess potent, broad-spectrum antifungal activity. We evaluated the in vitro activity of these investigational triazoles compared with that of itraconazole and amphotericin B against 239 clinical isolates of filamentous fungi from the SENTRY Program, including Aspergillus spp. (198 isolates), Fusarium spp. (7 isolates), Penicillium spp. (19 isolates), Rhizopus spp. (4 isolates), Mucor spp. (2 isolates), and miscellaneous species (9 isolates). The isolates were obtained from 16 different medical centers in the United States and Canada between January and December 2000. In vitro susceptibility testing was performed using the microdilution broth method outlined in the National Committee for Clinical Laboratory Standards M38-P document. Overall, posaconazole was the most active compound, inhibiting 94% of isolates at a MIC of ≤1 μg/ml, followed by voriconazole (91%), amphotericin B (89%), ravuconazole (88%), and itraconazole (70%). All three new triazoles demonstrated excellent activity (MIC, ≤1 μg/ml) against Aspergillus spp. (114 Aspergillus fumigatus, 22 Aspergillus niger, 13 Aspergillus flavus, 9 Aspergillus versicolor, 8 Aspergillus terreus, and 32 Aspergillus spp.): posaconazole (98%), voriconazole (98%), ravuconazole (92%), amphotericin B (89%), and itraconazole (72%). None of the triazoles were active against Fusarium spp. (MIC at which 50% of the isolates tested were inhibited [MIC50], >8 μg/ml) or Mucor spp. (MIC50, >8 μg/ml). Posaconazole and ravuconazole were more active than voriconazole against Rhizopus spp. (MIC50, 1 to 2 μg/ml versus >8 μg/ml, respectively). Based on these results, all three new triazoles exhibited promising activity against Aspergillus spp. and other less commonly encountered isolates of filamentous fungi. The clinical value of these in vitro data remains to be seen, and in vitro-in vivo correlation is needed for both new and established antifungal agents. Surveillance efforts should be expanded in order to monitor the spectrum of filamentous fungal pathogens and their in vitro susceptibility as these new antifungal agents are introduced into clinical use.

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