Phenotypic and Genotypic Analysis of Resistant Helicobacter pylori Strains Isolated from Children with Gastrointestinal Diseases.

Antibiotic resistance of Helicobacter pylori is currently a global issue. The aim of this study was to analyze actual antibiotic resistance rates of H. pylori strains isolated from children with primary infections and to compare the incidence of mutations that determine resistance to clarithromycin (CH) and metronidazole (MET) in children with different clinical diagnoses. A total of 91 H. pylori strains were isolated from 108 children with primary infections. Drug susceptibility testing of the strains was performed using E-test method. Classical sequencing of DNA fragments was used to detect point mutations for CH and MET resistance. Resistance to CH was detected in 31% of isolated strains (28/91), while resistance to MET and CH was detected in 35% (32/91) of strains. A2143G was the most frequently detected mutation and was dominant among strains isolated from children with peptic ulcer disease (80%). Mutations in the rdxA gene were found significantly more frequently among MET-resistant strains than MET-sensitive strains (p = 0.03, Chi2 = 4.3909). In children, a higher frequency of H. pylori multiresistant strains was observed compared with the previous study in the same area. Differences were found in the occurrence of point mutations among H. pylori strains resistant to CH isolated from children with different clinical diagnoses.

Molecular Patterns of Resistance Among Helicobacter pylori Strains in South-Western Poland.

Treatment failure of Helicobacter pylori infection is caused mainly by progressive antibiotic resistance among H. pylori strains. In Poland, the prevalence of H. pylori strains resistant to metronidazole is higher than in other developed countries, reaching almost 50%, and resistance to clarithromycin is as high as 30% and is still increasing, contributing to the failure of first-line therapy in approximately 70% of patients. Moreover, the introduction of levofloxacin to eradication therapy of H. pylori infection quickly led to the emergence of resistant strains. Therefore, a necessary approach in microbiological diagnostics of H. pylori infection should be determination of susceptibility of H. pylori strains before the eradication treatment. Aim: In this study was to evaluate the molecular mechanisms of resistance among 170 H. pylori strains to clarithromycin, involving mutations in the 23S rRNA gene (A2143G, A2142G, A2143G) and to levofloxacin, involving mutations of gyrA and gyrB. Analysis was performed by using polymerase chain reaction and classical sequencing of DNA fragments. Results: Among examined strains, 26% were fully sensitive and 74% were resistant to at least one of the tested antibiotics. The overall resistance rate to metronidazole was as high as 56%, whereas to clarithromycin 46%, respectively. Resistance to LEV occurred among 6% of strains. All tested strains were susceptible to AMC and TET. The A2143G point mutation was found in 72% of clarithromycin-resistant strains. The most common mutation, present in 40% of H. pylori strains resistant to levofloxacin, was a change at position 91 of gyrA. Conclusion: The increasing number of point mutations in the 23S rRNA gene leads to an increase in the rates of antimicrobial resistance. Presence of the GCG allele at position 122 of the gyrA gene may cause an eightfold increase in risk of development of resistance to levofloxacin.

Frequency of infection with Helicobacter pylori isolates of different antimicrobial profiles in children and adolescents: A preliminary study.

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.

The Prevalence of Helicobacter pylori Infection in Symptomatic Children: A 13-Year Observational Study in the Lower Silesian Region.

BACKGROUND: Helicobacter pylori (H. pylori) infection is very common worldwide, with varying frequency. According to data from epidemiological reports, a third of the population of children in Poland are infected with H. pylori before the age of 18. In recent years, a decrease in the incidence of H. pylori infection in both children and adults has been observed in many countries. OBJECTIVES: The aim of the study was to assess the prevalence H. pylori and non-helicobacter pylori helicobacter (NHPH) infection in symptomatic children from 2000 to 2013, and to analyze the resistance of H. pylori strains to antibiotics over the 13-year study period. MATERIAL AND METHODS: The retrospective analysis was based on the results of cultures for H. pylori in 8661 untreated children undergoing their first upper gastroduodenal endoscopy because of clinical symptoms such as chronic abdominal pain/distress, epigastric pain, nausea or vomiting. Drug sensitivity to three antibiotics - amoxicillin (AM), clarithromycin (CH) and metronidazole (MZ) - was determined by the gradient diffusion method (E-test). RESULTS: Overall, among 8661 cultures analyzed, 16.05% were positive for H. pylori. The highest prevalence of infection was found in the year 2000 (23.06%) and the lowest in the year 2010 (8.90%). The prevalence of NHPH infection was low (0.2%). A three-fold increase in the number of strains resistant to both CH and MZ was noted, from 7.9% to about 22.7%. All strains were susceptible to AM. CONCLUSIONS: There has been a decline in the prevalence of H. pylori infection in symptomatic children, but this infection is still a common cause of upper gastrointestinal tract symptoms in children treated at the authors' center. Primary antibiotic resistance of H. pylori increased over the period analyzed, but primary resistance to metronidazole declined.

Antimicrobial susceptibility of Helicobacter pylori isolates from Lower Silesia, Poland.

INTRODUCTION: In recent years the failure of standard therapy for Helicobacter pylori infections has been observed, which results primarily from the increasing resistance of H. pylori strains to antibiotics. The aim of the study was to estimate the prevalence of antimicrobial resistance of H. pylori strains isolated from adult symptomatic patients with primary infection in the Lower Silesia Region in Poland. MATERIAL AND METHODS: One hundred and seventy-eight adults aged 19-89 years with dyspeptic symptoms suggesting gastroduodenal pathology were enrolled in the study. The study was performed in the years 2008-2011. Fifty H. pylori strains were isolated from gastric biopsy samples of examined patients. Antimicrobial susceptibility to 6 drugs (amoxicillin (AM), clarithromycin (CH), metronidazole (MZ), tetracycline (TC), levofloxacin (LEV), and rifabutin (RB)) was tested by the gradient-diffusion method (E-test method). RESULTS: The incidence of H. pylori infection among examined patients was 35%. From 50 isolated H. pylori strains, 24% showed resistance to CH, 42% to MZ and 8% to LEV alone. Multidrug resistance was detected in 26% of strains, whereas 20% of isolates were resistant to MZ and CH. Examined strains were fully susceptible to AM, TC and RB. CONCLUSIONS: Resistance to clarithromycin strains isolated from adults of the Lower Silesia Region in Poland is high and is almost always associated with resistance to metronidazole (CH + MZ). It is necessary to continuously monitor H. pylori resistance to drugs used in therapy, especially to clarithromycin. Verification of the existing recommendations of eradication therapy is also needed.

The antimicrobial susceptibility of Helicobacter pylori strains isolated from children and adults with primary infection in the Lower Silesia Region, Poland.

The resistance of microorganisms to antibiotics has become a serious issue in recent years in the therapy of bacterial infections. This problem also concerns the treatment of infections caused by Helicobacter pylori strains. The aim of this study was to evaluate the frequency of primary resistance of H. pylori strains isolated from children and adults. The subject of the research was 105 strains of H. pylori isolated from children and 60 strains from adults in the Lower Silesia Region in the years 2008-2011. Antimicrobial susceptibility to the following antibiotics was assessed: amoxicillin (AC), clarithromycin (CH), metronidazole (MZ), tetracycline (TC), levofloxacin (LEV) and rifabutin (RB). Among the strains isolated from children, 33.3% were resistant to CH, 44.8% to MZ whereas 1.9% of strains were resistant simultaneously to CH, MZ and LEV. Among 60 strains isolated from adults, 23.3% were resistant to CH, 66.7% to MZ, and 6.7% to LEV. Moreover, 16 multidrug resistant strains were isolated from adults, including 12 resistant to CH and MZ, 3 to MZ and LEV, and 1 to CH, MZ and LEV. All examined strains were susceptible to AC, TC and RB. The high incidence of resistance to CH and MZ suggests that standard triple therapies may not be useful as first-line treatment in Poland without earlier susceptibility testing.