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

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 g/ml) and 21.5% were high-level resistant (MIC > 2 g/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-betalactam 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 g/ml. The MIC 90 s (MICs at which 90% of isolates were inhibited) of two ketolides were 0.06 g/ml (ABT773) and 0.12 g/ml (telithromycin). The MIC 90 of linezolid was 2 g/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.

Synthesis and Antibacterial Activity of a Novel Class of 15-Membered Macrolide Antibiotics, “11a-Azalides”

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Synthesis and antibacterial activity of novel 4″-carbamates of 6,11-di-O-methylerythromycin A

“…[1][2][3][4][5][6] There is a great need for new antibiotics that address the problem of antibiotic resistance. Under these circumstances, a substantial amount study has been carried out on novel macrolides.…”

Discovery of 4′′-Ether Linked Azithromycin-Quinolone Hybrid Series: Influence of the Central Linker on the Antibacterial Activity

“…In particular, these new leads maintain activity against MLS-resistant strains of Streptococcus pneumoniae and Streptococcus pyogenes. In addition, they represent an improvement over telithromycin (1) and cethromycin (2) against the fastidious Gram-negative pathogen Haemophilus influenzae.…”

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