Role of screening agar plates for in vitro susceptibility testing of Helicobacter pylori in a routine laboratory setting.
BACKGROUND
Resistance of Helicobacter pylori to the more frequently used antibiotics (metronidazole and clarithromycin) reduces eradication rates even with triple treatment. Determining the antibiogram profile of H pylori can take up to 14 days and delays appropriate treatment.


OBJECTIVE
To determine the role of screening agar plates for more rapid in vitro susceptibility of H pylori to metronidazole, amoxicillin, and clarithromycin.


METHODS
Routine gastric biopsy specimens from 507 dyspeptic patients were inoculated on to 10% lysed blood agar plates containing metronidazole (8 microg/ml), clarithromycin (2 microg/ml), or amoxicillin (0.5 microg/ml). The minimum inhibitory concentration (MIC) of the 90 isolates was determined using the E test.


RESULTS
Metronidazole resistance was detected in 28 of 90 isolates by E test and nine of 98 by screening agar. The screening agar detected none of the four clarithromycin resistant isolates detected by the E test.


CONCLUSIONS
The screening agar method is not sufficiently sensitive to be used alone.
Warburton-Timms
V J
VJ
Public Health Laboratory, Gloucestershire Royal Hospital, Great Western Road, Gloucester GL1 3NN, UK.
McNulty
C A
CA
D000328:Adult; D000362:Agar; D000658:Amoxicillin / Q000494:pharmacology; D017291:Clarithromycin / Q000494:pharmacology; D003470:Culture Media; D004352:Drug Resistance, Microbial; D016480:Helicobacter pylori / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods*; D013270:Stomach / Q000382:microbiology
D003470:Culture Media; D008795:Metronidazole; D000658:Amoxicillin; D000362:Agar; D017291:Clarithromycin