A multicentre correlation study of VITEK 2 with reference methods for telithromycin, mupirocin, and daptomycin against Staphylococcus spp.

Abstract number: 1134_02_406

Aldridge K.E., Dizney A., Thomson K., Procop G.

Objective:

Clinical studies have shown that appropriate antimicrobial therapy based on in vitro susceptibility data correlates with better patient outcome. VITEK 2 is a fully automated susceptibility testing methodology providing rapid(6–8 h) results for a variety of aerobic and facultatively anaerobic Gram-positive and -negative pathogens which have been shown to correlate to established reference methods. The objective of this study was to correlate the susceptibility results of Vitek 2 testing of telithromycin, mupirocin, and daptomycin against Staphylococcus spp. with those from reference methodology.

Methods:

Three geographically distinct clinical microbiology laboratories participated in the testing with each site testing 100 consecutive clinical islates and 84 blinded challenge isolates of staphylococci sent to each site.VITEK 2 testing was performed according to the manufacturer's recommendations. The challenge isolates were also tested using a manual preparation of the inoculum. NCCLS recommended reference agar and broth microdilution methods were used to test telithromycin, mupirocin, and daptomycin. MIC results were collated to determine the per cent (%) of isolates susceptible(S), intermediate(I), and resistant(R) based on CA-SFM, BSAC, and NCCLS recommended breakpoints. Essential(EA) and categorical(CA) agreements were then determined.

Results:

For telithromycin the MIC values indicated S,I,&R %s of 79.5,0.6,and 20.9 for clinical isolates and 76.2, 1.2, and 22.6 for the challenge isolates.EA and CA with reference methods were 100% for clinical isolates and 97.6% and 98.8% for challenge isolates.Overall for telithromycin the EA and CA were 99.5% and 99.7%. For mupirocin the MIC values indicated S and R %s of 88.5 and 11.5 for clinical isolates and 98.8 and 1.2 for the challenge isolates. EA and CA were 99.7% and 99% for clinical isolates and 100% for the challenge isolates. Overall the EA and CA for mupirocin were 99.7% and 99.2% respectively. 100% of isolates were S to daptomycin. EA was 98% for clinical isolates; 99.1% for challenge isolates; and overall was 98.2% for daptomycin.

Conclusion:

Using both clinical and challenge isolates of Staphylococcus spp. VITEK 2 results showed a high correlation with reference method results for each agent. EA and CA significantly exceeded regulatory requirements for equivalence between VITEK 2 and reference methodologies.