Little research has been conducted on determining the vancomycin susceptibility of MRSA using a reference microdilution.
Using a reference microdilution method, we determined the MIC of vancomycin for isolates from 123 consecutive patients with nosocomial MRSA bacteremia.
Minor errors occurred when an organism was considered susceptible or resistant either by the reference microdilution method or with the tested system but intermediate by the other method.
MICs, determined by the EUCAST reference microdilution method (6 ), after 48 h of incubation were >8, 2, >8, 0.5, and >8 µg/mL for amphotericin B, itraconazole, voriconazole, posaconazole, and caspofungin, respectively.
Furthermore, there has been little research examining the use of reference microdilution as a method of vancomycin susceptibility determination [ 9].
Additionally, there is discordance between the MIC result from an Etest and the value determined using the reference microdilution method.
Antimicrobial susceptibility tests are performed by broth microdilution by using NCCLS reference methods (16) either on-site (for non-US laboratories) or by a reference laboratory (for US participants).
VISA is currently defined as a vancomycin MIC of 4 8 μg/ml by reference broth microdilution (BMD) and hVISA as MIC ≤ 2 μg/ml with subpopulations of VISA determined by a plating-based, population analysis profile-area under the curve (PAP-AUC) method (Pfeltz et al. 2001; Satola et al. 2009).
Consecutive non-duplicate bacterial isolates (prevalence design) were collected from patients with documented infections in 410 medical centres and were susceptibility tested by reference broth microdilution methods.
The organisms tested by reference broth microdilution methods were Staphylococcus aureus (3156), coagulase-negative staphylococci (CoNS; 856), enterococci (901), Streptococcus pneumoniae (619), and viridans group (223) or β-hemolytic streptococci (358); also, D-test was used to determine inducible clindamycin resistance in Staphylococcus aureus.
