Gatifloxacin Resistance and Mutations in gyrA after Unsuccessful Helicobacter pylori Eradication in Japan

Abstract

A high resistance rate (47.9%) to gatifloxacin (GAT; 8-methoxy fluoroquinolone) in Helicobacter pylori (H. pylori) strains from 48 Japanese patients is observed after unsuccessful H. pylori eradication. A significant association between MICs for GAT equal to or above 1 g/ml and mutations of the gyrA gene of H. pylori was demonstrated.Resistance to antibiotics is the major cause of the failure to eradicate Helicobacter pylori. For such cases, alternative regimens need to be developed.Perri et al. have reported an unacceptable low eradication rate of only 68% with a 7-day regimen of levofloxacin (LVX), amoxicillin (AMX), and pantoprazole (12). However, Sharara et al. have recently reported an excellent eradication rate of 92% with a 7-day regimen of gatifloxacin (GAT), AMX, and rabeprazole (14). It is important to note the superior in vitro activity of GAT over that of LVX against H. pylori (1). Therefore, GAT-based triple therapy might be a promising option for an alternative treatment regimen.Several studies have shown that the "quinolone resistancedetermining region" (QRDR) of the gyrA gene plays a critical role in the resistance of H. pylori to ciprofloxacin (CIP) (8,15). H. pylori does not contain genes for topoisomerase IV, an important fluoroquinolone target in other bacteria (15). The present study demonstrated a correlation between MICs to GAT and mutations of the gyrA and gyrB genes in H. pylori isolated from Japanese patients after unsuccessful eradication of infection.A total of 48 patients (32 males and 16 females; mean age, 57.8) with H. pylori infection after treatment failure were enrolled at Keio University Hospital between September 2004 and June 2005. Of the total, 42 patients had one treatment failure, 4 patients had two treatment failures, and 2 patients had three treatment failures (first-line treatment, triple therapy with clarithromycin [CLR], AMX, and proton pump inhibitor [PPI]; second-line treatment, triple therapy with metronidazole [MNZ], AMX, and PPI; and third-line treatment, triple therapy with LVX, AMX, and PPI). All patients underwent upper gastrointestinal endoscopy and gastric biopsy at Keio University Hospital.The susceptibility of H. pylori isolates to CRL, GAT, and MNZ was determined by the agar dilution method according to the guidelines established by the CLSI (formerly NCCLS) (9). Isolates were considered resistant to MNZ if the MIC of the drug was Ն8 g/ml and resistant to CLR and GAT if the MIC of these drugs was Ն1 g/ml (3, 7, 10). The resistance rates to GAT, CLR, and MNZ were 47.9%, 79.2%, and 6.3%, respectively. The GAT resistance rates were 22.2% (2/9) in the strains susceptible to both CLR and MNZ, 50% (18/36) in the strains resistant to CLR but susceptible to MNZ, 100% (1/1) in the strains resistant to MNZ but susceptible to CLR, and 100% (2/2) in the strains resistant to both CLR and MNZ.Studies in Europe have suggested that the primary resistance rate might be as low as 8% for CIP (2, 16) and that only 9% of the isolates show resistance to CIP after failure of pr...

Rapid Detection of Point Mutations Conferring Resistance to Fluoroquinolone in gyrA of Helicobacter pylori by Allele-Specific PCR

“…All patients underwent upper-gastrointestinal endoscopy; biopsy specimens obtained from the greater curvature of the upper corpus were then used to isolate H. pylori. The clinical isolates of H. pylori used in the present study were previously examined and reported only in terms of gyrA mutation and the MIC for GAT (17). In addition to 48 previous isolates (17), isolates with known GAT MICs were examined for gyrA mutation (KS0203, KS0205, KS0193, and KS0195).…”

“…The MIC was defined as the lowest concentration of antibiotic that completely inhibited the growth of the inoculum. Isolates were considered resistant to GAT if the MIC of the drug was Ն1 g/ml (2,11,14,17).…”

“…Therefore, GAT-based triple therapy might be a promising alternative treatment option for H. pylori infection. However, we recently reported a high resistance rate (47.9%) to GAT of Helicobacter pylori strains isolated from Japanese patients after unsuccessful eradication therapy (17).…”

“…The resistance of H. pylori to fluoroquinolones, which exert their antimicrobial action by affecting the A subunit of the DNA gyrase of H. pylori, has been reported to be caused by point mutations in the so-called quinolone resistance-determining region of the gyrA gene of H. pylori (9,12,17,19,22,23), mainly at amino acid 87 (Asn to Lys) or 91 (Asp to Gly, Asp to Asn, or Asp to Tyr) (17,22). H. pylori does not possess a gene encoding topoisomerase IV, an important fluoroquinolone target in other bacteria.…”

Acquisition of double mutation in gyrA caused high resistance to sitafloxacin in Helicobacter pylori after unsuccessful eradication with sitafloxacin-containing regimens

“…PCR was performed with 35 cycles of denaturation at 94 C for 30 seconds (s), annealing at 52 C for 30 s, and extension at 72 C for one minute. 4,5,8,12 PCR products for sequencing were purified with a QIAquick Gel Extraction Kit (QIAGEN). PCR templates of all strains were sequenced directly on both strands by the BigDye Terminator Cycle Sequencing method using the Applied Biosystems 3100 Genetic Analyzer (Applied Biosystems).…”