A review of in-vitro antibacterial activity of quinupristin/dalfopristin against methicillin-susceptible and -resistant Staphylococcus aureus.
Methicillin-resistant Staphylococcus aureus (MRSA) presently represents approximately 30% of clinical isolates of S. aureus in the USA. Many strains are additionally resistant to erythromycin, 15- and 16-membered macrolides (e.g. azithromycin, spiramycin), clindamycin, aminoglycosides and/or quinolones. A review of the literature shows that quinupristin/dalfopristin, a semisynthetic derivative of pristinamycin, exhibits good in-vitro activity against methicillin-sensitive S. aureus and MRSA (mean MIC90 0.25-1.0 and 0.5-2.0 mg/L, respectively). Its in-vitro bacteriostatic activity is also unaffected by resistance phenotypes for erythromycin, ciprofloxacin, rifampicin or gentamicin. Among erythromycin-resistant MRSA strains, those with constitutive (macrolide and lincosamide) resistance are only 2-fold less sensitive as strains with inducible (14- and 15-membered macrolide only) resistance (MICs 0.5-1.0 and 0.25-1.0 mg/L, respectively). Quinupristin/dalfopristin is at least as active as vancomycin and more active than ciprofloxacin and erythromycin against MRSA. It generally has a more rapid bactericidal action than vancomycin and oxacillin against many strains of MRSA. The bactericidal activity of quinupristin/dalfopristin may be affected by macrolide resistance phenotype: S. aureus strains susceptible or inducibly resistant to macrolides are killed within 6 h, whereas a number of strains constitutively resistant to macrolides remain viable after 12 h. The clinical significance of this laboratory phenomenon requires investigation, possibly in additional animal models of infection.
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DE
Department of Microbiology, Mount Sinai Hospital, Toronto, Ontario, Canada.
Nadler
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HL
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000379:methods; D010641:Phenotype; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development; D014769:Virginiamycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D014769:Virginiamycin; C062940:quinupristin-dalfopristin