title: Antimicrobial resistance of Helicobacter pylori strains to five antibiotics, including levofloxacin, in Northwestern Turkey.
abstract: BACKGROUND
  Antibiotic resistance is the main factor that affects the efficacy of current therapeutic regimens against Helicobacter pylori. This study aimed to determine the rates of resistance to efficacy clarithromycin, amoxicillin, tetracycline, levofloxacin and metronidazole among H. pylori strains isolated from Turkish patients with dyspepsia.
  
  
  METHODS
  H. pylori was cultured from corpus and antrum biopsies that were collected from patients with dyspeptic symptoms, and the antimicrobial susceptibility of H. pylori was determined using the E-test (clarithromycin, amoxicillin, tetracycline, metronidazole and levofloxacin) according to the EUCAST breakpoints. Point mutations in the 23S rRNA gene of clarithromycin-resistant strains were investigated using real-time PCR.
  
  
  RESULTS
  A total of 98 H. pylori strains were isolated, all of which were susceptible to amoxicillin and tetracycline. Of these strains, 36.7% (36/98) were resistant to clarithromycin, 35.5% (34/98) were resistant to metronidazole, and 29.5% (29/98) were resistant to levofloxacin. Multiple resistance was detected in 19.3% of the isolates. The A2143G and A2144G point mutations in the 23S rRNA-encoding gene were found in all 36 (100%) of the clarithromycin-resistant strains. Additionally, the levofloxacin MIC values increased to 32 mg/L in our H. pylori strains. Finally, among the clarithromycin-resistant strains, 27.2% were resistant to levofloxacin, and 45.4% were resistant to metronidazole.
  
  
  CONCLUSIONS
  We conclude that treatment failure after clarithromycin- or levofloxacin-based triple therapy is not surprising and that metronidazole is not a reliable agent for the eradication of H. pylori infection in Turkey.
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Reyhan
authors.initials: R
authors.lastname: Caliskan
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Hrisi Bahar
authors.initials: HB
authors.lastname: Tokman
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Gastroenterology, Istanbul University, Istanbul, Turkey.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Erzin
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Suat
authors.initials: S
authors.lastname: Saribas
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Pelin
authors.initials: P
authors.lastname: Yuksel
authors.affiliation: Medical Laboratory Techniques Program, Vocational School of Health Services, Istanbul Esenyurt University, Istanbul, Turkey.
authors.forename: Bora Kazim
authors.initials: BK
authors.lastname: Bolek
authors.affiliation: Faculty of Arts and Sciences, Department of Biology, Fatih University, Istanbul, Turkey.
authors.forename: Ecehan Ozge
authors.initials: EO
authors.lastname: Sevuk
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Demirci
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Ozge
authors.initials: O
authors.lastname: Yılmazli
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Ozer
authors.initials: O
authors.lastname: Akgul
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Fatma
authors.initials: F
authors.lastname: Kalayci
authors.affiliation: Institute of Forensic Sciences,, Department of Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Huseyin
authors.initials: H
authors.lastname: Cakan
authors.affiliation: Faculty of Arts and Sciencs, Department of Biology, Fatih University, Istanbul, Turkey.
authors.forename: Barik
authors.initials: B
authors.lastname: Salih
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Gastroenterology, Istanbul University, Istanbul, Turkey.
authors.forename: Kadir
authors.initials: K
authors.lastname: Bal
authors.affiliation: Cerrahpasa Faculty of Medicine, Department of Medical Microbiology, Istanbul University, Istanbul, Turkey.
authors.forename: Bekir
authors.initials: B
authors.lastname: Kocazeybek
mesh_terms: D000328:Adult; D000368:Aged; D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004415:Dyspepsia / Q000382:microbiology*; D005260:Female; D016480:Helicobacter pylori / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D064704:Levofloxacin / Q000494:pharmacology; D008297:Male; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011446:Prospective Studies; D013752:Tetracycline / Q000494:pharmacology; D014421:Turkey; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D008795:Metronidazole; D064704:Levofloxacin; D000658:Amoxicillin; D013752:Tetracycline; D017291:Clarithromycin