Comparative in vitro activities of linezolid, quinupristin-dalfopristin, moxifloxacin, and trovafloxacin against erythromycin-susceptible and -resistant streptococci.
The in vitro activities of the new agents linezolid, quinupristin-dalfopristin, moxifloxacin, and trovafloxacin were determined and compared with those of penicillin, clindamycin, and four macrolides against 53 erythromycin-resistant Streptococcus pneumoniae, 117 S. pyogenes (64 erythromycin-susceptible and 53 -resistant), and 101 S. agalactiae (53 erythromycin-susceptible and 48 -resistant) isolates. Differentiation of macrolide resistance phenotypes was performed by the double-disk method. The genetic basis for macrolide resistance in 52 strains was also determined. The M phenotype was found in 84.9, 6.3, and 1.9% of S. pyogenes, S. agalactiae, and S. pneumoniae isolates, respectively. These strains were susceptible to miocamycin and clindamycin. Strains with the inducible phenotype accounted for 27.1% of S. agalactiae isolates and 9.4% each of S. pyogenes and S. pneumoniae isolates. All erythromycin-resistant isolates were also resistant to the 14- and 15-membered macrolides tested. Strains with all three phenotypes were susceptible to </=2 microgram of linezolid per ml. Quinupristin-dalfopristin exhibited good in vitro activity against all strains, irrespective of their resistance to erythromycin (MICs at which 90% of the isolates tested were inhibited [MIC(90)s], 0.2 to 1 microgram/ml). Against the erythromycin-resistant S. pyogenes and S. agalactiae strains, moxifloxacin and trovafloxacin were the most active agents (MIC(90)s, 0.1 microgram/ml). The new antimicrobials evaluated may be alternative agents to treat infections caused by macrolide-resistant as well as macrolide-susceptible streptococci.
Betriu
C
C
Servicio de Microbiología Clínica, Hospital Clínico San Carlos, 28040 Madrid, Spain. cbetriu@efd.net
Redondo
M
M
Palau
M L
ML
Sánchez
A
A
Gómez
M
M
Culebras
E
E
Boloix
A
A
Picazo
J J
JJ
D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001372:Aza Compounds; D004352:Drug Resistance, Microbial / Q000502:physiology; D004359:Drug Therapy, Combination / Q000494:pharmacology; D004917:Erythromycin / Q000494:pharmacology; D024841:Fluoroquinolones; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009287:Naphthyridines / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D023303:Oxazolidinones; D011804:Quinolines; D013291:Streptococcus / Q000187:drug effects*; D014769:Virginiamycin / Q000494:pharmacology
D000081:Acetamides; D000900:Anti-Bacterial Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D009287:Naphthyridines; D010080:Oxazoles; D023303:Oxazolidinones; D011804:Quinolines; D014769:Virginiamycin; C062940:quinupristin-dalfopristin; D004917:Erythromycin; C080163:trovafloxacin; D000069349:Linezolid; D000077266:Moxifloxacin