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 Emergence of Penicillin-ResistantStreptococcus Pneumoniaein Southern Ontario, 1993–94

1995 ◽  
Vol 6 (3) ◽  
pp. 157-160 ◽  
Author(s):  
Andrew E Simor ◽  
Anita Rachlis ◽  
Lisa Louie ◽  
Janet Goodfellow ◽  
Marie Louie
Keyword(s):  
Antimicrobial Agents ◽  
Clinical Laboratory ◽  
Tertiary Care ◽  
National Committee ◽  
In Vitro Susceptibility ◽  
Southern Ontario ◽  
Recent Emergence ◽  
Resistant Strains ◽  
High Level

Objective: To determine the prevalence of resistance ofStreptococcus pneumoniaeto penicillin and other antimicrobial agents in metropolitan Toronto.Design: Consecutive pneumococcal isolates from different patients were obtained from two private community-based laboratories and from patients assessed in the emergency department of a tertiary-care teaching hospital in Toronto, Ontario between June and December 1993, and between March and October 1994. In vitro susceptibility testing was done by broth microdilution in accordance with National Committee for Clinical Laboratory Standards guidelines.Results: Twenty (7.3±3.1%) of 274 pneumococcal isolates were resistant to penicillin; six (30%) isolates had high-level resistance (minimal inhibitory concentration [mic] 2.0 μg/mL or greater); and 14 isolates had intermediate resistance (mic0.1 to 1.0 μg/mL). Penicillin-resistant strains were also frequently resistant to tetracycline (55%), cotrimoxazole (50%), erythromycin (40%) and cefuroxime (35%). Resistant strains comprised several serotypes: 19F (six isolates), 9V (three), 23F (three), and one each of 6A, 6B, 14, and 19A; four isolates were nontypeable.Conclusions: There has been a recent emergence of penicillin-resistantS pneumoniaein southern Ontario. National and regional surveillance is warranted to determine the extent of the problem elsewhere in Canada.

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 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.

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 Emergence of high rates of antimicrobial resistance among viridans group streptococci in the United States.

1996 ◽  
Vol 40 (4) ◽  
pp. 891-894 ◽  
Author(s):  
G V Doern ◽  
M J Ferraro ◽  
A B Brueggemann ◽  
K L Ruoff
Keyword(s):  
United States ◽  
Antimicrobial Resistance ◽  
Blood Culture ◽  
Rank Order ◽  
The United States ◽  
Medical Centers ◽  
Streptococcus Milleri ◽  
Intermediate Resistance ◽  
High Level ◽  
Viridans Group Streptococci

Three hundred fifty-two blood culture isolates of viridans group streptococci obtained from 43 U.S. medical centers during 1993 and 1994 were characterized. Included were 48 isolates of "Streptococcus milleri," 219 S. mitis isolates, 29 S. salivarius isolates, and 56 S. sanguis isolates. High-level penicillin resistance (MIC, > or = 4.0 micrograms/ml) was noted among 13.4% of the strains; for 42.9% of the strains, penicillin MICs were 0.25 to 2.0 micrograms/ml (i.e., intermediate resistance). In general, amoxicillin was slightly more active than penicillin. The rank order of activity for five cephalosporins versus viridans group streptococci was cefpodoxime = ceftriaxone > cefprozil = cefuroxime > cephalexin. The percentages of isolates resistant (MIC, > or = 2 micrograms/ml) to these agents were 15, 17, 18, 20, and 96, respectively. The rates of resistance to erythromycin, tetracycline, and trimethoprim-sulfamethoxazole were 12 to 38%. Resistance to either chloramphenicol or ofloxacin was uncommon (i.e., < 1%). In general, among the four species, S. mitis was the most resistant and "S. milleri" was the most susceptible.

scholarly journals Antimicrobial Resistance in Respiratory Tract Streptococcus pneumoniae Isolates: Results of the Canadian Respiratory Organism Susceptibility Study, 1997 to 2002

2003 ◽  
Vol 47 (6) ◽  
pp. 1867-1874 ◽  
Author(s):  
George G. Zhanel ◽  
Lorraine Palatnick ◽  
Kimberly A. Nichol ◽  
Tracy Bellyou ◽  
Don E. Low ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Antimicrobial Resistance ◽  
Antibiotic Consumption ◽  
Multidrug Resistant ◽  
Medical Centers ◽  
Intermediate Resistance ◽  
Susceptibility Study ◽  
Resistant Strains ◽  
Canadian Provinces ◽  
High Level

ABSTRACT A total of 6,991 unique patient isolates of Streptococcus pneumoniae were collected from October 1997 to June 2002 from 25 medical centers in 9 of the 10 Canadian provinces. Among these isolates, 20.2% were penicillin nonsusceptible, with 14.6% being penicillin intermediate (MIC, 0.12 to 1 μg/ml) and 5.6% being penicillin resistant (MIC, ≥2 μg/ml). The proportion of high-level penicillin-resistant S. pneumoniae isolates increased from 2.4 to 13.8% over the last 3 years of the study, and the proportion of multidrug-resistant S. pneumoniae isolates increased from 2.7 to 8.8% over the 5-year period. Resistant rates (intermediate and resistant) among non-β-lactam agents were as follows: macrolides, 9.6 to 9.9%; clindamycin, 3.8%; doxycycline, 5.5%; chloramphenicol, 3.9%; and trimethoprim-sulfamethoxazole, 19.0%. Rates of resistance to non-β-lactam agents were higher among penicillin-resistant strains than among penicillin-susceptible strains. No resistance to vancomycin or linezolid was observed; however, 0.1% intermediate resistance to quinupristin-dalfopristin was observed. The rate of macrolide resistance (intermediate and resistant) increased from 7.9 to 11.1% over the 5 years. For the fluoroquinolones, the order of activity based on the MICs at which 50% of isolates are inhibited (MIC50s) and the MIC90s was gemifloxacin > clinafloxacin > trovafloxacin > moxifloxacin > grepafloxacin > gatifloxacin > levofloxacin > ciprofloxacin. The investigational compounds ABT-773 (MIC90, 0.008 μg/ml), ABT-492 (MIC90, 0.015 μg/ml), GAR-936 (tigecycline; MIC90, 0.06 μg/ml), and BMS284756 (garenoxacin; MIC90, 0.06 μg/ml) displayed excellent activities. Despite decreases in the rates of antibiotic consumption in Canada over the 5-year period, the rates of both high-level penicillin-resistant and multidrug-resistant S. pneumoniae isolates are increasing in Canada.

scholarly journals Molecular Relationships and Antimicrobial Susceptibilities of Viridans Group Streptococci Isolated from Blood of Neutropenic Cancer Patients

1999 ◽  
Vol 37 (6) ◽  
pp. 1876-1880 ◽  
Author(s):  
H. Wisplinghoff ◽  
R. R. Reinert ◽  
O. Cornely ◽  
H. Seifert
Keyword(s):  
Clinical Laboratory ◽  
Hematologic Malignancies ◽  
Penicillin Resistance ◽  
National Committee ◽  
Cross Transmission ◽  
Neutropenic Patients ◽  
Molecular Relationships ◽  
High Level ◽  
Resistance Rates ◽  
Viridans Group Streptococci

From January 1995 to May 1998, 57 episodes of bacteremia due to viridans group streptococci were identified in 50 febrile neutropenic patients with hematologic malignancies. Four patients experienced two separate episodes of streptococcal bacteremia, and one patient had four separate episodes of streptococcal bacteremia. Strains were identified to species level as Streptococcus mitis (n= 37), Streptococcus oralis (n = 19), andStreptococcus salivarius (n = 1). Epidemiologic relatedness of these strains was studied by using PCR-based fingerprinting with M13 and ERIC-2 primers and pulsed-field gel electrophoresis with restriction enzyme SmaI. All strains that were isolated from different patients exhibited unique fingerprint patterns, thus suggesting that viridans group streptococcal bacteremia usually derives from an endogenous source. Cross-transmission of strains between patients could not be established. Four S. mitis isolates recovered during four separate bacteremic episodes in a single patient had identical fingerprint patterns. Susceptibility testing was carried out by broth microdilution technique according to National Committee for Clinical Laboratory Standards guidelines. The MICs at which 90% of the isolates are inhibited were (in milligrams per liter) as follows: 0.5 (penicillin), 0.5 (amoxicillin), 0.25 (cefotaxime), 2 (chloramphenicol), 4 (erythromycin), 0.5 (clindamycin), ≥32 (tetracycline), ≥32 (trimethoprim-sulfamethoxazole), 4 (ciprofloxacin), 0.5 (sparfloxacin), 0.5 (vancomycin), 0.25 (teicoplanin), and 1 (quinupristin-dalfopristin). High-level penicillin resistance (MIC, ≥4 mg/liter) was found in one isolate only, but intermediate penicillin resistance was noted in 11 isolates (19%). Resistance rates to other drugs were as follows: 7% (amoxicillin), 4% (cefotaxime), 4% (chloramphenicol), 32% (erythromycin), 9% (clindamycin), 39% (tetracycline), 68% (trimethoprim-sulfamethoxazole), 23% (ciprofloxacin), 0% (sparfloxacin), 0% (vancomycin), 0% (teicoplanin), and 0% (quinupristin-dalfopristin).

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.

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