BACKGROUND: Helicobacter pylori (H. pylori) infection can occur as a mixed infection caused by several strains of H. pylori. OBJECTIVES: The aim of the study was to determine the frequency of colonization of the gastric mucosa by strains of H. pylori with different susceptibility to antimicrobial agents. MATERIAL AND METHODS: The study was carried out on gastric biopsies taken from 54 previously untreated Polish children and adolescents. Of the 15 positive cultures, from each primary medium, 6 single H. pylori colonies were isolated, making a total of 90 isolates, and the susceptibility to metronidazole (MZ), amoxicillin (AC) and clarithromycin (CH) was determined by E-test method. The presence of the cagA gene and vacA alleles (s1, s2, m1, m2) was determined by PCR. RESULTS: Positive culture for H. pylori was noted in 15/54 (27.7%) of patients. All H. pylori isolates were susceptible to AC, 27.8% were resistant to MZ and 38.9% to CH. The results showed 7/15 (46.7%) of children were infected with H. pylori strains with antibiotic heteroresistance, resistant to CH (5/15, 33.3%) and to MZ (2/15, 13.3%). The cagA + vacA s1/m2 combination was predominant genotype among detected H. pylori strains. The isolates possessing different antimicrobial susceptibility profiles in the same patient were identified. CONCLUSIONS: Microbiological analyses confirmed the presence of isolates possessing different antimicrobial susceptibility profiles in 47% of examined children with H. pylori infection. Different antimicrobial susceptibility profiles of H. pylori isolates detected in the same patient may influence the success of eradication therapy.
BACKGROUND:Helicobacter pylori (H. pylori) infection can occur as a mixed infection caused by several strains of H. pylori. OBJECTIVES: The aim of the study was to determine the frequency of colonization of the gastric mucosa by strains of H. pylori with different susceptibility to antimicrobial agents. MATERIAL AND METHODS: The study was carried out on gastric biopsies taken from 54 previously untreated Polish children and adolescents. Of the 15 positive cultures, from each primary medium, 6 single H. pylori colonies were isolated, making a total of 90 isolates, and the susceptibility to metronidazole (MZ), amoxicillin (AC) and clarithromycin (CH) was determined by E-test method. The presence of the cagA gene and vacA alleles (s1, s2, m1, m2) was determined by PCR. RESULTS: Positive culture for H. pylori was noted in 15/54 (27.7%) of patients. All H. pylori isolates were susceptible to AC, 27.8% were resistant to MZ and 38.9% to CH. The results showed 7/15 (46.7%) of children were infected with H. pylori strains with antibiotic heteroresistance, resistant to CH (5/15, 33.3%) and to MZ (2/15, 13.3%). The cagA + vacA s1/m2 combination was predominant genotype among detected H. pylori strains. The isolates possessing different antimicrobial susceptibility profiles in the same patient were identified. CONCLUSIONS: Microbiological analyses confirmed the presence of isolates possessing different antimicrobial susceptibility profiles in 47% of examined children with H. pyloriinfection. Different antimicrobial susceptibility profiles of H. pylori isolates detected in the same patient may influence the success of eradication therapy.