[In vitro activity of clarithromycin and metronidazole against Helicobacter pylori in different incubation atmospheres].
The aim of this study was to determine the in vitro activity of clarithromycin and metronidazole using an agar dilution method to compare two different incubation atmospheres: a CO2 incubator and a jar with a microaerobic gas-generating system. Antibiotics were placed on plates in twofold dilutions ranging from 128 to 0.064 mg/l in Mueller-Hinton agar supplemented with 7% horse blood. The inoculum was prepared from 31 Helicobacter pylori isolates and was inoculated using a Steers replicator. Plates were incubated for 3 to 5 days and MICs were recorded as the lowest concentration of antibiotic inhibiting visible growth. Two different incubation atmospheres were used: a CO2 incubator set at 95% humidity and 10% CO2, and a jar with a gas-generating envelope that produces 7-10% O2 and 14% CO2 (BioMerieux). Clarithromycin resistance was found in 19% of strains both in the gas-generating system and the CO2 incubator. Metronidazole resistance was 23% in both atmospheres. MICs for clarithromycin in both atmospheres showed two dilutions of difference for 100% of the strains, and were slightly higher in the jar with a gas-generating envelope. However, MICs for metronidazole were higher when it was incubated in the CO2 incubator, and in 86.7% of strains the MICs showed < or = 2 dilutions of difference. No great discrepancies were found for either metronidazole or clarithromycin using the two methods.
Alarcón
T
T
Servicio de Microbiología, Hospital Universitario de la Princesa, Madrid, Spain. talarcon@helicobaters.pain.com
Domingo
D
D
Prieto
N
N
de la Obra
P
P
López-Brea
M
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques; D017291:Clarithromycin / Q000494:pharmacology*; D016480:Helicobacter pylori / Q000187:drug effects*; D008795:Metronidazole / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D008795:Metronidazole; D017291:Clarithromycin