title: Serious streptococcal infections produced by isolates resistant to streptogramins (quinupristin/dalfopristin): case reports from the SENTRY antimicrobial surveillance program.
abstract: The emergence and sustained prevalence of Gram-positive organisms resistant to antimicrobials has been of interest for over a decade. Quinupristin/dalfopristin (formerly RP 59500 or Synercid) is a new injectable streptogramin combination that has been reported to have activity against Gram-positive organisms, even those with documented MLS(B) resistance. However, the two case reports presented here illustrate three well-documented Streptococcus spp. strains (S. mitis, S. pneumoniae) to be resistant to quinupristin/dalfopristin (MICs at 3, 8, and 12 microg/ml) following referral as routine isolates in the SENTRY Antimicrobial Surveillance Program. The S. pneumoniae pleural fluid isolate was cross-resistant to erythromycin. Both bacteremic S. mitis strains were resistant to macrolides (erythromycin, azithromycin, clarithromycin), lincosamides (clindamycin), and fluoroquinolones. Patient histories indicated no prior use of MLS class antimicrobials for the S. mitis case, but the patient having the S. pneumoniae isolate did receive prior treatment of erythromycin and clindamycin. All isolates had modestly increased penicillin MICs of 0.12 microg/ml. The mode of resistance to quinupristin/dalfopristin was not evident (sat A-negative by PCR); and these cases illustrate the existence of streptogramin-resistant isolates before the introduction of this antimicrobial class into human clinical practice.
authors.affiliation: Medical Microbiology Division, Department of Pathology, University of Iowa College of Medicine, Iowa City, IA, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Kugler
authors.forename: G A
authors.initials: GA
authors.lastname: Denys
authors.forename: M L
authors.initials: ML
authors.lastname: Wilson
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D004352:Drug Resistance, Microbial; D005260:Female; D006801:Humans; D008297:Male; D013290:Streptococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013291:Streptococcus / Q000187:drug effects* / Q000302:isolation & purification; D014769:Virginiamycin / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D014769:Virginiamycin; C113825:quinupristin; C113826:dalfopristin