Evaluation of Four Methods for Antimicrobial Susceptibility Testing of Helicobacter pylori in Routine Practice

Kang, Jung Oak; Han, Dongsoo; Choi, Tae Yeal

Abstract

BACKGROUND
We compared currently available four antimicrobial susceptibility test methods for H.pylori to find out a practical method suitable for testing a few strains of H.pylori at a time in the clinical microbiology laboratory.
METHODS
With 37 clinical isolates of H.pylori, antimicrobial susceptibility tests were performed against amoxicillin (AMX), clarithromycin (CLR), and metronidazole (MTZ) using disk diffusion method with egg yolk emulsion (EYE) media, E test with EYE and Mueller Hinton blood agar plate (MH BAP), and modified broth microdilution methods (mBMD).
RESULTS
The results of AMX and CLR showed a complete agreement between the four methods. For MTZ, however, a significant discrepancy was observed between the results obtained by the four methods. In four strains exhibiting high minimal inhibitory concentrations (MIC, > or =32 mg/L) to MTZ, category agreement was excellent, but correlation was not good in 13 strains with the MTZ MICs of 8 to 16 mg/L. In 20 strains with MTZ MICs between 0.25 mg/L and 4 mg/L, category agreement was excellent, but correlation between MICs or inhibitory zone diameters was not good. Etest EYE and Etest MH BAP methods showed a 100% agreement in the susceptibility category of MTZ.
CONCLUSION
In routine practice, the most practical method for testing susceptibility of H.pylori to AMX and CLR seems to be the disk diffusion method with EYE or MH BAP. But for MTZ, a duplicate test using both Etest and disk diffusion test is recommended until more standardized, economical, and technically easier test methods become available.