High Prevalence of Clarithromycin-Resistant Helicobacter pylori Strains and Risk Factors Associated with Resistance in Madrid, Spain

Abstract

Clarithromycin is one of the antibiotics used for the treatment of Helicobacter pylori infections, and clarithromycin resistance is the most important factor when it comes to predicting eradication failure. The present study analyzed H. pylori isolates for the presence of 23S rRNA gene mutations and determined the risk factors associated with resistance among H. pylori isolates collected in Madrid, Spain, in 2008. We studied 118 H. pylori strains isolated from the same number of patients. A total of 76.3% of the patients were born in Spain, 52.7% were children, 20.3% had previously been treated, and 66.1% were female. Clarithromycin resistance was determined by Etest. H. pylori strains were considered resistant if the MIC was >1 mg/liter. DNA extraction was carried out by use of the NucliSens easyMAG platform with NucliSens magnetic extraction reagents (bioMérieux). The DNA sequences of the 23S rRNA genes of clarithromycin-resistant and -sensitive strains were determined to identify specific point mutations. The vacA genotype and cagA status were determined by PCR. We found that 42 (35.6%) strains were resistant to clarithromycin by Etest. Etest results were confirmed by detection of the presence of point mutations in 34 (88.1%) of these strains. Eight H. pylori strains were resistant to clarithromycin by Etest but did not have a point mutation in the 23S rRNA gene. Mutation at A2143G was found in 85.3% of the strains, mutation at A2142G in 8.8%, and mutation at T2182C in 5.9%. Dual mutations were found in 8.8% of the strains. H. pylori clarithromycin-resistant strains were strongly associated with pediatric patients, with patients born in Spain, and with patients who had previously been treated (P < 0.02). In addition, H. pylori strains resistant to clarithromycin more frequently presented the vacA s2/m2 genotype and were more likely to be cagA negative than susceptible strains (39.1% and 11.2%, respectively; P value < 0.001). We concluded that, in the present study, H. pylori clarithromycin-resistant strains are more frequently found in children, in patients mostly born in Spain, and in individuals who were previously treated for H. pylori infection and that these individuals are more likely colonized with a less virulent H. pylori strain.

Prevalence of A2143G and A2144G Point Mutations Responsible for Clarithromycin Resistance among Helicobacter pylori Strains in Bushehr, Iran

“…In fact, the primary risk factor for resistance to clarithromycin is the previous use of clarithromycin or other macrolides (20). It should be emphasized that cross-resistance to different types of macrolides can be developed (5,20).…”

“…However, resistance to antibiotics is a major problem in effective treatment (2). Clarithromycin is the most effective antimicrobial used for the treatment of H. pylori infection, and resistance to this drug is the major cause of treatment failure (3)(4)(5). The prevalence of clarithromycin resistance may vary in different geographical regions, and continuous monitoring of the clarithromycin resistance rate in each region is important for designing the most effective therapies (6,7).…”

“…Clarithromycin attaches to the peptidyl transferase region of 23S rRNA and inhibits protein synthesis (5). Resistance to clarithromycin in H. pylori is caused predominantly by point mutations in the peptidyl transferase center of 23S rRNA (5,8,9).…”

“…Resistance to clarithromycin in H. pylori is caused predominantly by point mutations in the peptidyl transferase center of 23S rRNA (5,8,9). These mutations prevent the binding of clarithromycin to the 50S subunit of the ribosome (6).…”

PCR detection of clarithromycin-susceptible and -resistant Helicobacter pylori from formalin-fixed, paraffin-embedded gastric biopsies

“…Several previous reports have described the identification of clarithromycin-resistant H. pylori by PCR from clinical specimens, using cultures grown from gastric biopsies 12,18,19 and more recently from formalin-fixed, paraffin-embedded gastric biopsy tissue. 20 The use of a PCR assay to detect clarithromycinresistant H. pylori in formalin-fixed, paraffinembedded tissues offers several potential advantages over culture-based methods.…”