Comparison of the effects of anaerobic and micro-aerophilic incubation on resistance of Helicobacter pylori to metronidazole.
To assess the influence of incubation conditions on the resistance of Helicobacter pylori this study compared the effect of micro-aerophilic and anaerobic incubation followed by micro-aerophilic incubation on the measurement of metronidazole resistance of 102 H. pylori isolates, by both disk diffusion and Epsilometer (E)-tests. Anaerobic incubation for 24 h before micro-aerophilic incubation for 48 h consistently increased metronidazole activity in both assay methods. Although statistically significant, this was microbiologically less significant, as only 4 of 102 isolates gave discrepant readings (all four were resistant in micro-aerophilic conditions but susceptible in anaerobic/micro-aerophilic conditions). In all four cases variation was by a few millimeters in zone size (i.e., all were close to the cut-off point). There was 100% agreement between disk diffusion and E-test results. Of 104 observations (52 duplicate assays: 13 strains, two atmospheric conditions, two methods of determining resistance) there was 100% intra-observer and inter-observer agreement with regard to susceptibility and resistance status for both E-test and disk diffusion methods. Anaerobic incubation followed by micro-aerophilic incubation had little effect on the estimation of prevalence of metronidazole resistance and seemed to add little, if any, significant advantage over micro-aerophilic incubation alone.
Abdi
Y M
YM
Young
K A
KA
Department of Medical Microbiology, Royal London Hospital Trust, 37 Ashfield Street, London E1 1BB.
Rampton
D S
DS
Department of Oral Microbiology, St Bartholomew's and The Royal London School of Medicine and Dentistry, Turner Street, London E1 2AD.
Hardie
J M
JM
Gastrointestinal Science Research Unit, St Bartholomew's and The Royal London School of Medicine and Dentistry, 26 Ashfield Street, London E1 2AJ.
Feldman
R A
RA
Department of Epidemiology, St Bartholomew's and The Royal London School of Medicine and Dentistry, Turner Street, London E1 1BB.
Banatvala
N
N
Department of Epidemiology, St Bartholomew's and The Royal London School of Medicine and Dentistry, Turner Street, London E1 1BB.
D000332:Aerobiosis; D000693:Anaerobiosis; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016480:Helicobacter pylori / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D008795:Metronidazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015588:Observer Variation; D013270:Stomach / Q000382:microbiology
D000900:Anti-Bacterial Agents; D008795:Metronidazole