Distribution of gyrA mutations in fluoroquinolone-resistant Helicobacter pylori strains.
OBJECTIVE
To investigate the resistance of Helicobacter pylori (H. pylori) to ciprofloxacin (CIP), levofloxacin (LVX) and moxifloxacin (MOX) in the Beijing area and to elucidate the resistance mechanisms.


METHODS
Seventy-nine H. pylori clinical strains, isolated from patients who had undergone upper gastrointestinal endoscopy in Peking University First Hospital from 2007 to 2009, were tested for their susceptibility to CIP, LVX and MOX using the E-test method. H. pylori strain 26695 was included in the susceptibility testing as a control strain. According to the minimal inhibitory concentration (MIC) values, a strain was classified as resistant to CIP, LVX or MOX when the MIC was > 1 microg/mL. We amplified by polymerase chain reaction (PCR) and sequenced the quinolone resistance-determining regions of the gyrA and gyrB genes from 29 quinolone-resistant and 16 quinolone-susceptible H. pylori strains selected at random.


RESULTS
In this study, the resistance rates of H. pylori to CIP, LVX or MOX were 55.7% (44/79), and the primary resistance rates were 26.6% (21/79). Patients with secondary resistance had received LVX in previous eradication treatments, but not MOX or CIP. Forty-five strains, including 29 CIP, LVX or MOX-resistant strains (MIC: 1.5-32 microg/mL) and 16 susceptible strains, were selected randomly from the 79 strains and used in PCR analysis. Among these 45 strains, 27 resistant strains had mutations in the gyrA gene, including 11 strains with mutations corresponding to Asp-91 (MIC: 2-32 microg/mL), one of which also had a mutation corresponding to Val-150, and 16 strains had mutations at Asn-87 (MIC: 4-32 microg/mL), three of which also had mutations corresponding to Arg-140 or Val-150. In addition, Arg-140, Val-150 or Ala-97 mutations were separately detected in three susceptible strains. Analysis of the gyrB gene showed that one strain of low resistance had a mutation corresponding to Ser-457 that coexisted with an Asp-91 mutation. There was a significant difference in the occurrence of mutations in the gyrA gene between CIP, LVX and MOX-resistant and -susceptible strains (P < 0.05), but 2 resistant strains were found to possess no quinolone resistance-determining region mutations.


CONCLUSIONS
Resistance is primarily mediated through point mutations in gyrA. Whether other mechanisms are responsible for resistance in strains without mutations in the QRDR should be detected.
Wang
Li-Hui
LH
Department of Gastroenterology, Peking University First Hospital, Beijing 100034, China.
Cheng
Hong
H
Hu
Fu-Lian
FL
Li
Jiang
J
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D002681:China; D027081:DNA Gyrase / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology; D005798:Genes, Bacterial; D016481:Helicobacter Infections / Q000188:drug therapy / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D009154:Mutation
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D027081:DNA Gyrase
J Antimicrob Chemother. 2005 Nov;56(5):965-7
16159928
Antimicrob Agents Chemother. 1991 Aug;35(8):1647-50
1656869
Helicobacter. 2009 Feb;14(1):61-5
19191898
World J Gastroenterol. 2006 Apr 21;12(15):2398-401
16688832
BMC Gastroenterol. 2009 May 26;9:38
19470177
Int J Antimicrob Agents. 2007 Apr;29(4):389-96
17303392
Helicobacter. 2009 Oct;14(5):77-85
19751431
Antimicrob Agents Chemother. 1989 Feb;33(2):254-5
2655532
Gut. 2007 Jun;56(6):772-81
17170018
Clin Infect Dis. 2007 Jan 15;44(2):e5-8
17173210
Gut. 2004 Jan;53(1):34-7
14684573
Aliment Pharmacol Ther. 2002 Mar;16(3):527-32
11876707
Aliment Pharmacol Ther. 2007 Oct 1;26(7):1063-7
17877513
Int J Antimicrob Agents. 2005 Jun;25(6):542-5
15876526
Helicobacter. 2007 Oct;12(5):518-22
17760720
Chemotherapy. 2008;54(1):50-3
18073471
World J Gastroenterol. 2004 Mar 1;10(5):668-71
14991935
JAMA. 2004 Jan 14;291(2):187-94
14722144
Helicobacter. 2006 Oct;11(5):441-5
16961806
World J Gastroenterol. 2006 Apr 21;12(15):2313-9
16688818
J Dig Dis. 2008 Aug;9(3):178-84
18956598
Antimicrob Agents Chemother. 2000 Feb;44(2):248-54
10639345
Helicobacter. 2004 Feb;9(1):9-16
15156899
Sex Transm Dis. 2004 Oct;31(10):616-8
15389000
Zhonghua Yi Xue Za Zhi. 2008 Oct 21;88(38):2722-5
19080698
Aliment Pharmacol Ther. 2003 Oct 15;18(8):815-20
14535875
Nature. 1997 Aug 7;388(6642):539-47
9252185
Chin Med J (Engl). 2003 Jan;116(1):11-4
12667379
Helicobacter. 2006 Aug;11(4):243-9
16882327