Affiliation:
1. Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain
2. Departments of Medicine and Microbiology, NYU School of Medicine, New York, New York
Abstract
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.
Publisher
American Society for Microbiology
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