Helicobacter Pylori

Helicobacter pylori is a Gram-negative, microaerophilic bacterium found in the stomach. It is linked to the development of duodenal ulcers and chronic active gastritis. Infected persons are increased risk for lymphoma and gastric cancer. At least half the world’s population is infected by the bacterium, making it the most widespread infection in the world. The developing world has much higher infection rates than the industrialized countries. However, in Alaska, the overall seroprevalence among Alaska Native persons is approximately 75%, which is more common than in the general U.S. population. The aim of this study is to monitor antimicrobial resistance of H. pylori isolates over time and by region in Alaska Native patients.

In this paper, H. pylori data from January 2000 to December 2008 were analyzed from four of the five sentinel surveillance sites: the Alaska Native Medical Center (ANMC) in Anchorage, Kanakanak Hospital in Dillingham, the Yukon-Kuskokwim Delta Regional Hospital (YKDRH) in Bethel, and the Norton Sound Regional Hospital (NSRH) in Nome. Antral and fundal biopsy specimens are obtained from patients undergoing esophagogastroduodenoscopy (EGD). The specimens were cultured and antimicrobial susceptibility testing of the H. pylori isolates was performed in the CDC Arctic Investigations Program (AIP) laboratory.

Biopsy specimens were also stained with Diff-Quik stain for identification of H. pylori isolates and with hematoxylin and eosin stain for histological evaluation. MIC testing by agar dilution was performed according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). MIC testing for levofloxacin was conducted by Etest. MIC breakpoints used for antimicrobial drug resistance are a metronidazole MIC of > 8µg/ml, an amoxicillin MIC of ≥ 1µg/ml, a levofloxacin MIC of ≥ 2µg/ml, a clarithromycin MIC of ≥ 1µg/ml, and a tetracycline MIC of ≥ 2µg/ml. Statistical analyses were conducted by using SAS software. P values of <0.05 were considered statistically significant.

Overall, 45% (532/1,181) of patient specimens were culture positive for H. pylori. In detail, Metronidazole resistance was shown in isolates from 222/531 (42%) patients, clarithromycin resistance in 159/531 (30%) patients, amoxicillin resistance in 10/531(2%) patients, and levofloxacin resistance in 30/155 (19%) patients. No tetracycline resistance was examined. The prevalence of antimicrobial drug resistance varies by regions. More female patients than male patients were to demonstrate metronidazole (P < 0.05) and clarithromycin (P < 0.05) resistance. No change was observed in the proportion of patients with resistant isolates over time.

Conclusion: among H. pylori isolates from Alaska Native patients, the resistance to metronidazole, clarithromycin, and levofloxacin is more common than those from elsewhere in the U.S. The data are useful for informing antibiograms treatment of H. pylori infections in Alaska.