Korean J Clin Microbiol.  2005 Oct;8(2):160-164.

Evaluation of Vitek and Disk Diffusion Susceptibility Testing of Enterobacteriaceae against Piperacillin-Tazobactam and Methicillin-Resistant Staphylococcus aureus against Trimethoprim-Sulfamethoxazole

• Song W
• Lee TJ
• Kim TK
• Kim HS
• Kim JS
• Park MJ
• Lee KM

Abstract

BACKGROUND
The aim of this study was to evaluate the Vitek system and the disk diffusion method for susceptibility testing of Enterobacteriaceaeagainst piperacillin-tazobactam (TZP) and methicillin-resistant Staphylococcus aureus (MRSA) against trimethoprim-sulfamethoxazole (SXT)using the broth microdilution method as the reference.
METHODS
Using the Vitek system and the disk diffusion method, we tested 96 isolates of Enterobacteriaceae (48 Escherichia coli, 26 Klebsiella pneumoniae, 8 Serratia marcescens, 6 Enterobacter cloacae, 2 E. aerogenes, 2 K. oxytoca, 2 Citrobacter freundii, 2 Pantoea agglomerans) and 61 isolates of MRSA for susceptibity against TZP and SXT, respectively; the broth microdilution of National Committee for Clinical Laboratory Standards was used as the reference method.
RESULTS
In the susceptibility testing of Enterobacteriaceae against TZP, Vitek system yielded 10 (10%) minor errors, and the disk diffusion method one (1%) very major and 13 (14%) minor errors. For the MRSA against SXT, the rate of categorical agreement between the reference method and the Vitek or the disk diffusion method was both 100%. The rates of agreement between the reference method and the Vitek system in term of MICs (within +/-1 dilution) were 93% and 98% in the susceptibility testing of Enterobacteriaceae against TZP and MRSA against SXT, respectively.
CONCLUSION
Both Vitek system and disk diffusion method showed an acceptable level of accuracy for the susceptibility test of Enterobacteriaceaeagainst TZP and MRSA against SXT.

Keyword

Enterobacteriaceae; Methicillin-resistant Staphylococcus aureus; Piperacillintazobactam; Trimethoprim-sulfamethoxazole; Vitek; Disk diffusion

MeSH Terms

Citrobacter freundii
Diffusion*
Enterobacter cloacae
Enterobacteriaceae*
Escherichia coli
Klebsiella pneumoniae
Methicillin Resistance*
Methicillin-Resistant Staphylococcus aureus*
Pantoea
Serratia marcescens
Trimethoprim, Sulfamethoxazole Drug Combination*