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ABSTRACTSolid and liquid media supplemented only with a cyanobacterial extract (CE) and free of fetal calf serum (FCS), blood, and its derivatives support the growth of Helicobacter pylori. A total of 11 strains of H. pyloriisolated from gastric biopsy samples were successfully subcultured in Mueller-Hinton agar supplemented with 0.4% CE. When this medium was used for primary isolation of H. pylori, a low isolation rate (30%) was observed because of the abundant growth of contaminants. The growth kinetics of eight isolates and H. pylorireference strain NCTC 11638 in Mueller-Hinton broth (MHB) supplemented with 0.7% CE were estimated by use of growth parameters, and the results were compared with those obtained with MHB-5% FCS. For four strains the cellular concentrations obtained with CE were statistically higher (P< 0.05) than those obtained with FCS, and in some cases these values were similar to the highest values reported in the literature. Depending on the strain, the specific growth rates obtained with CE were similar to or increased compared with those obtained with FCS. The replacement of FCS by CE in H. pyloricultures would facilitate the retrieval of cultures with high cellular densities as a source of cellular and extracellular proteins free of serum. Also, CE has advantages over conventional supplements, such as easier conservation and compliance with the pressing tendency at present to avoid the use of products derived from animals.

ABSTRACTClarithromycin and metronidazole resistance was 29.1 and 23.9%, respectively, in 96 Helicobacter pyloristrains obtained from pediatric patients. No resistance to amoxicillin was observed. Resistance according to patients' ages to clarithromycin and metronidazole was 45.4 and 18.2% in 22 patients from 4 to 8 years old, 30.2 and 20.7% in 53 patients from 9 to 13 years old, and 9.5 and 38.1% in 21 patients from 14 to 18 years old, respectively. The A2143G mutation was the most prevalent (82.1%) among clarithromycin-resistant strains.