Re‐assessment of the disk diffusion technique for routine antimicrobial susceptibility testing for Helicobacter pylori

Abstract

BackgroundThe aim of this study was to assess the disk diffusion technique against E‐test as a routine antibiotic susceptibility testing method for Helicobacter pylori.Materials and methodsSusceptibilities of 301 H pylori clinical isolates were simultaneously profiled by E‐test and disk diffusion method for levofloxacin (5‐μg disk), clarithromycin (15‐μg disk), metronidazole (5‐μg disk), amoxicillin (10‐μg disk), and tetracycline (30‐μg disk). Furazolidone susceptibility was evaluated using a 100‐μg disk only. The correlation between MICs by E‐test and inhibition zone diameters by disk diffusion was assessed by linear regression analysis.ResultsCorrelation between inhibition zone diameters and MICs was found for levofloxacin (r = −.932), clarithromycin (r = −.894), and to a minor extent metronidazole (r = −.820). Using the linear regression analysis, the inhibition zone diameter breakpoints were calculated to be 29 mm for levofloxacin, 41 mm for clarithromycin, and 15 mm for metronidazole corresponding to the EUCAST‐recommended MIC breakpoints. The susceptibility agreement between E‐test and disk diffusion for levofloxacin, clarithromycin, and metronidazole was 98.6%, 96.0%, and 96.7%, respectively. The inhibition zone diameters recorded for the amoxicillin, tetracycline, and furazolidone were large (approximately 60 mm in mean), and a poor correlation was found between inhibition zone diameters and MICs for amoxicillin (r = −.594) and tetracycline (r = −.490).ConclusionsThe disk diffusion can be used as a routine H pylori susceptibility testing method for levofloxacin, clarithromycin, and metronidazole in clinical practice under the described technical conditions. The use of disk diffusion for amoxicillin, tetracycline, and furazolidone susceptibility testing needs to be further studied.

Need for standardization and harmonization of Helicobacter pylori antimicrobial susceptibility testing

“…Several studies have demonstrated satisfactory susceptibility agreement between the disk diffusion method and agar dilution or E‐test methods for testing H . pylori resistance to CLR, LEV, and MTZ 13–18 . With susceptibility of 301 clinical H pylori isolates simultaneously tested by E‐test and disk diffusion methods for CLR (15‐μg disk), LEV (5‐μg disk), and MTZ (5‐μg disk), our group demonstrated good correlation between the inhibition zone diameters by disk diffusion and the MICs by E‐test 13 .…”

“…pylori resistance to CLR, LEV, and MTZ 13–18 . With susceptibility of 301 clinical H pylori isolates simultaneously tested by E‐test and disk diffusion methods for CLR (15‐μg disk), LEV (5‐μg disk), and MTZ (5‐μg disk), our group demonstrated good correlation between the inhibition zone diameters by disk diffusion and the MICs by E‐test 13 . Using the linear regression analysis, the inhibition zone diameter breakpoints were calculated to be 41 mm for CLR, 29 mm for LEV, and 15 mm for MTZ corresponding to the EUCAST‐recommended MIC breakpoints (>0.5, >1, >8 mg/L as resistance to CLR, LEV and MTZ, respectively).…”

“…Using the linear regression analysis, the inhibition zone diameter breakpoints were calculated to be 41 mm for CLR, 29 mm for LEV, and 15 mm for MTZ corresponding to the EUCAST‐recommended MIC breakpoints (>0.5, >1, >8 mg/L as resistance to CLR, LEV and MTZ, respectively). The satisfactory susceptibility agreement (>95%) between the disk diffusion and E‐test methods was observed for CLR, LEV, and MTZ 13 . However, since there are no globally harmonized disk diffusion methodology parameters (including the medium to be used, the inoculum density, the incubation condition and time, the criteria for measuring the growth inhibition zone diameter, especially the MIC breakpoint to be used as resistance reference) for H .…”

Frequency and antibiotic resistance of Helicobacter pullorum among exposed and non-exposed population

“…It is thought that the use of novel antibiotics is indispensable for controlling the outbreak of new infectious diseases (26). The reason why the disk diffusion method was used in this study could be that this method is cost-effective, less time consuming, and user friendly in clinical practice (27). Moreover, there have been several reports demonstrating the usefulness of this method for analyzing the phenotypic resistance of the microaerophilic bacteria like Helicobacter or Campylobacter in humans and poultry throughout the world (7,(25)(26)(27)(28)(29)(30).…”

“…The reason why the disk diffusion method was used in this study could be that this method is cost-effective, less time consuming, and user friendly in clinical practice (27). Moreover, there have been several reports demonstrating the usefulness of this method for analyzing the phenotypic resistance of the microaerophilic bacteria like Helicobacter or Campylobacter in humans and poultry throughout the world (7,(25)(26)(27)(28)(29)(30). However, given that there are very few studies about the antibiogram of H. pullorum among people with gastroenteritis, the results of the present study could not be fully supported (31,32).…”