Helicobacter pylori Culture with Antimicrobial Susceptibilities
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Helicobacter pylori is a spiral, gram-negative bacterium that is present in virtually all patients with idiopathic chronic duodenal ulceration. Helicobacter pylori has been implicated as the etiological agent of antral gastritis and may predispose to gastric carcinoma. While the organism is strongly associated with gastrointestinal disease, it is also estimated that 40% to 60% of asymptomatic Caucasians older than 60 years are Helicobacter pylori-colonized. Recommended noninvasive tests to detect active Helicobacter pylori infection include the urea breath test or fecal antigen detection. On gastric biopsy specimens, diagnosis of Helicobacter pylori infection may be made by the rapid urease test, histopathology, or culture. Serology is also available; however, results cannot distinguish between active infection or past exposure.
Multidrug regimens are required to attain successful cure rates (exceeding 90%) for Helicobacter pylori infection. Preferred treatment includes metronidazole (or an alternate nitroimidazole), clarithromycin, amoxicillin, tetracycline, and/or a quinolone,as part of the multidrug regimen. The prevalence of Helicobacter pylori strains resistant to either metronidazole or clarithromycin has been increasing. Infections with Helicobacter pylori strains resistant to clarithromycin or metronidazole have been associated with a greater incidence of treatment failure than infections with susceptible strains.
The Clinical and Laboratory Standards Institute (CLSI) has recommended an agar dilution method for Helicobacter pylori susceptibility testing. Amoxicillin, ciprofloxacin, clarithromycin, metronidazole and tetracycline are routinely tested. However, the only antimicrobial for which susceptibility categories are defined is clarithromycin.
Recovery of Helicobacter pylori from gastric specimens to facilitate antimicrobial susceptibility testing used to guide antimicrobial therapy
A positive result provides definitive evidence of the presence of Helicobacter pylori. Organisms may be detected in asymptomatic (colonized) individuals. False-negative culture results do occur since the organism may die between biopsy collection and laboratory culture.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Culture-negative results may occur due to the fastidious nature of the organism. Culture should be set up as soon as possible following specimen collection.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
No growth after 7 days
Susceptibility results are reported as MIC in mcg/mL.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Blaser MJ: Helicobacter pylori and the pathogenesis of gastroduodenal inflammation. J Infect Dis 1990;161:626-633
2. Ormand JE, Talley NJ: Helicobacter pylori: controversies and an approach to management. Mayo Clin Proc 1990;65:414-426
3. Versalovic J, Fox JG: Helicobacter. In Manual of Clinical Microbiology, Seventh edition. Edited by PR Murray. Washington DC, 1999, pp 727-738
4. Theel ES: Helicobacter pylori Infection: Test Utilization Strategies for Diagnosis. Mayo Medical Laboratories Communique 2013;38(6):1-8