ru-66647 and dalfopristin

We have studied the prevalence of the different macrolide, lincosamide, streptograminB (MLS(B)) phenotypes among clinical Staphylococcus aureus isolates erythromycin- and/or oxacillin-resistant; and also the activity of other antimicrobial agents including telithromycin, quinupristin/dalfopristin, linezolid, aminoglycosides, chloramphenicol and vancomycin. We found that 64.86% of S. aureus were oxacillin-resistant. While the most prevalent MLS(B) phenotype among methicillin-resistant S. aureus (MRSA) was constitutive MLS(B) (cMLS) (83%), among methicillin-susceptible S. aureus (MSSA) it was inducible MLS(B) (iMLS(B)) (90%). Kanamycin resistance was more frequent than resistance to other aminoglycosides, being 100% for MRSA. Telithromycin was only active against iMLS(B), MS and erythromycin-susceptible isolates, although resistance rates were found among iMLS(B) MSSA (2.78%). Quinupristin/dalfopristin showed greater activity, with resistance rates of 2.5% for MRSA and 1.53% for MSSA. Both vancomycin and linezolid were fully active against all the isolates tested, with the highest MIC value being 2 microg/ml and 4 microg/ml, respectively. Among MRSA strains, 81.67% displayed resistance to five or more antimicrobials. This multiresistance was more frequently found among cMLS(B) strains (96.38% MRSA resistant to 6-9 agents).

Topics: Acetamides; Drug Resistance, Multiple, Bacterial; Humans; Ketolides; Linezolid; Macrolides; Microbial Sensitivity Tests; Oxazolidinones; Sampling Studies; Sensitivity and Specificity; Spain; Staphylococcus aureus; Virginiamycin

This study evaluated the current status of antimicrobial resistance in clinical isolates of Streptococcus pyogenes in Taiwan as part of the SMART (Surveillance from Multicenter Antimicrobial Resistance in Taiwan) program. In 2001, 419 different isolates of S. pyogenes, including 275 from respiratory secretions, 87 from wound pus, and 31 from blood, were collected from nine hospitals in different parts of Taiwan. MICs of 23 antimicrobial agents were determined at a central location by the agar dilution method. All of the isolates were susceptible to penicillin (MIC at which 90% of the isolates were inhibited [MIC(90)], moxifloxacin > ciprofloxacin = levofloxacin = gatifloxacin > gemifloxacin) demonstrated potent activity against nearly all of the isolates of S. pyogenes tested. Thirty-two isolates (8%) were not susceptible to quinupristin-dalfopristin. Seventeen percent of isolates had telithromycin MICs of >or=1 microg/ml, and all of these isolates exhibited erythromycin MICs of >or=32 microg/ml. The high prevalence of resistance to telithromycin (which is not available in Taiwan) limits its potential use in the treatment of S. pyogenes infections, particularly in areas with high rates of macrolide resistance.

Topics: Anti-Bacterial Agents; Drug Resistance, Bacterial; Erythromycin; Genes, Bacterial; Humans; Ketolides; Macrolides; Microbial Sensitivity Tests; Phenotype; Streptococcal Infections; Streptococcus pyogenes; Taiwan; Virginiamycin

Screening by ofloxacin disk was carried out on 1158 strains of Streptococcus pneumoniae in order to investigate the in vitro bacteriostatic activity of penicillin G, levofloxacin, moxifloxacin, telithromycin, linezolid, pristinamycin and quinupristin-dalfopristin against ofloxacin-intermediate and -resistant S. pneumoniae strains. It was concluded that these new antimicrobial agents could be useful for the treatment of pneumococcal infections caused by penicillin-sensitive and -resistant S. pneumoniae, and would represent a valid therapeutic option for patients allergic to beta-lactams, should they prove to be potent in vivo.

Topics: Acetamides; Anti-Bacterial Agents; Anti-Infective Agents; Aza Compounds; Drug Resistance, Bacterial; Fluoroquinolones; Ketolides; Lactams; Levofloxacin; Linezolid; Macrolides; Microbial Sensitivity Tests; Moxifloxacin; Ofloxacin; Oxazolidinones; Penicillin G; Pristinamycin; Quinolines; Streptococcus pneumoniae; Virginiamycin

Macrolide-resistance was assessed in 216 consecutive Streptococcus pyogenes isolates from throat infections in the region of Aachen, Germany. Seventeen isolates were resistant to erythromycin: 12 isolates revealed a macrolide (M) phenotype and harbored mefA, and five strains expressed an inducible macrolide-lincosamide-streptogramin B (MLSB) phenotype of which four strains harbored ermA(TR) and one strain contained ermB(AM). Telithromycin (HMR 3647) and quinupristin/dalfopristin remained active particularly against the ermA(TR)-containing S. pyogenes isolates studied. Random amplified polymorphic DNA analysis identified multiple clones among erythromycin-resistant strains, but did not discriminate beyond the emm-type. mefA was present in three isolates either with emm2, emm12, or emm75, and in nine isolates with emm4. All four strains with ermA(TR) contained emm77, and the single strain with ermB(AM) harbored emm1. Despite the relative low rate of macrolide-resistance, these data suggest that at least three different macrolide-resistance determinants are prevalent in Germany and that mefA has spread rapidly into multiple clones of S. pyogenes.

Topics: Anti-Bacterial Agents; Drug Resistance; Erythromycin; Genotype; Germany; Ketolides; Macrolides; Microbial Sensitivity Tests; Pharynx; Phenotype; Polymorphism, Restriction Fragment Length; Regulon; Respiratory Tract Infections; Reverse Transcriptase Polymerase Chain Reaction; Streptococcal Infections; Streptococcus pyogenes; Streptogramins; Virginiamycin

The susceptibilities of Mycoplasma hominis, Mycoplasma pneumoniae, and Ureaplasma urealyticum to eight new antimicrobial agents were determined by agar dilution. M. pneumoniae was susceptible to the new glycylcycline GAR-936 at 0.12 microg/ml and evernimicin at 4 microg/ml, but it was resistant to linezolid. It was most susceptible to dirithromycin, quinupristin-dalfopristin, telithromycin, reference macrolides, and josamycin. M. hominis was susceptible to linezolid, evernimicin, and GAR-936. It was resistant to macrolides and the ketolide telithromycin but susceptible to quinupristin-dalfopristin and josamycin. U. urealyticum was susceptible to evernimicin (8 to 16 microg/ml) and resistant to linezolid. It was less susceptible to GAR-936 (4.0 microg/ml) than to tetracycline (0.5 microg/ml). Telithromycin and quinupristin-dalfopristin were the most active agents against ureaplasmas (0.06 microg/ml). The new quinolone gatifloxacin was active against M. pneumoniae and M. hominis at 0.12 to 0.25 microg/ml and active against ureaplasmas at 1.0 microg/ml. The MICs of macrolides were markedly affected by pH, with an 8- to 32-fold increase in the susceptibility of M. pneumoniae as the pH increased from 6.9 to 7.8. A similar increase in susceptibility with increasing pH was also observed with ureaplasmas. Tetracyclines showed a fourfold increase of activity as the pH decreased 1 U, whereas GAR-936 showed a fourfold decrease in activity with a decrease in pH.

Topics: 4-Quinolones; Acetamides; Aminoglycosides; Anti-Bacterial Agents; Aza Compounds; Erythromycin; Fluoroquinolones; Gatifloxacin; Humans; Hydrogen-Ion Concentration; Ketolides; Linezolid; Macrolides; Microbial Sensitivity Tests; Minocycline; Moxifloxacin; Mycoplasma hominis; Mycoplasma pneumoniae; Oxazolidinones; Quinolines; Tetracyclines; Tigecycline; Ureaplasma urealyticum; Virginiamycin