title: Characterisation of a Staphylococcus aureus strain with progressive loss of susceptibility to vancomycin and daptomycin during therapy.
abstract: Following an initial response to vancomycin therapy, a patient with meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia developed endocarditis, failed a second course of vancomycin and then failed daptomycin therapy. An increase in the vancomycin minimum inhibitory concentrations of four consecutive MRSA blood isolates from 2 microg/mL to 8 microg/mL was shown by Etest. Population analysis of four successive blood culture isolates recovered over the 10-week period showed that the MRSA strain became progressively less susceptible to both vancomycin and daptomycin. Retrospectively, the macro Etest method using teicoplanin indicated a decrease in vancomycin susceptibility in the second blood isolate. The patient improved after treatment with various courses of trimethoprim/sulfamethoxazole, quinupristin/dalfopristin and linezolid. Early detection of vancomycin-heteroresistant S. aureus isolates, which appeared to have clinical significance in this case, continues to be a challenge for the clinical laboratory. Development of suitable practical methods for this should be given priority. Concurrent development of resistance to vancomycin and daptomycin, whilst rare, must be considered in a patient who is unresponsive to daptomycin following vancomycin therapy.
authors.affiliation: Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Atlanta, GA 30333, USA.
authors.forename: Fred C
authors.initials: FC
authors.lastname: Tenover
authors.forename: Scott W
authors.initials: SW
authors.lastname: Sinner
authors.forename: Robert E
authors.initials: RE
authors.lastname: Segal
authors.forename: Vanthida
authors.initials: V
authors.lastname: Huang
authors.forename: Shandline S
authors.initials: SS
authors.lastname: Alexandre
authors.forename: John E
authors.initials: JE
authors.lastname: McGowan
authors.forename: Melvin P
authors.initials: MP
authors.lastname: Weinstein
mesh_terms: D000081:Acetamides / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology; D017576:Daptomycin / Q000627:therapeutic use*; D024881:Drug Resistance, Bacterial; D004697:Endocarditis, Bacterial / Q000188:drug therapy / Q000382:microbiology; D006801:Humans; D000069349:Linezolid; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000627:therapeutic use; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology*; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000627:therapeutic use; D014640:Vancomycin / Q000627:therapeutic use*; D014769:Virginiamycin / Q000627:therapeutic use
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D014769:Virginiamycin; C062940:quinupristin-dalfopristin; D014640:Vancomycin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D000069349:Linezolid; D017576:Daptomycin