title: Pattern of primary resistance of Helicobacter pylori to metronidazole or clarithromycin in the United States.
abstract: BACKGROUND
  Therapy for Helicobacter pylori is generally empiric despite the fact that resistance to metronidazole and clarithromycin compromise therapeutic efficacy. The aim of this study was to aid clinicians in choosing a course of therapy for H pylori infection in the United States.
  
  
  METHODS
  The frequency of primary clarithromycin and metronidazole resistance among H pylori isolated from patients enrolled in US-based clinical trials between 1993 and 1999 was reviewed in relation to patient age, sex, region of the United States, and test method (Etest and 2 agar dilution procedures).
  
  
  RESULTS
  Clarithromycin and metronidazole resistance rates were based on the results of 3439 pretreatment Etest determinations and 3193 agar dilution determinations. Sex and age were available on 900 and 823 individuals, respectively. Metronidazole resistance was 39% by Etest and 21.6% by agar dilution (P<.001). Clarithromycin resistance was 12% by Etest and 10.6% by agar dilution. Amoxicillin or tetracycline resistance was rare. Metronidazole and clarithromycin resistance was more common in women than men (eg, 34.7% vs 22.6% for metronidazole and 14.1% vs 9.7% for clarithromycin (P =.01 and P =.06, respectively). Antibiotic resistance increased gradually up to age 70 years, then declined significantly (P<.05) regardless of test method. Regional differences in antimicrobial resistance did not occur.
  
  
  CONCLUSIONS
  While age and sex had significant effects on resistance rates, regional differences were not present. The high prevalence of resistance to metronidazole and clarithromycin may soon require the performance of antimicrobial susceptibility testing of H pylori isolates prior to initiating treatment.
authors.affiliation: Gastroenterology Microbiology Laboratory, Department of Medicine, Veterans Affairs Medical Center, MS 111D, 2002 Holcombe Boulevard, Houston, TX 77030. mosato@bcm.tmc.edu
authors.forename: M S
authors.initials: MS
authors.lastname: Osato
authors.forename: R
authors.initials: R
authors.lastname: Reddy
authors.forename: S G
authors.initials: SG
authors.lastname: Reddy
authors.forename: R L
authors.initials: RL
authors.lastname: Penland
authors.forename: H M
authors.initials: HM
authors.lastname: Malaty
authors.forename: D Y
authors.initials: DY
authors.lastname: Graham
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000994:Antitrichomonal Agents / Q000627:therapeutic use*; D017291:Clarithromycin / Q000627:therapeutic use*; D004352:Drug Resistance, Microbial; D016481:Helicobacter Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000472:pathogenicity; D006801:Humans; D008795:Metronidazole / Q000627:therapeutic use*; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D000994:Antitrichomonal Agents; D008795:Metronidazole; D017291:Clarithromycin