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-shaped gram-negative bacterium which may cause chronic gastritis, peptic ulcer disease, and/or gastric neoplasia. In adults of industrialized countries, an estimated 0.5% of the susceptible population becomes infected each year, although the incidence has been decreasing over time. The organism may asymptomatically colonize humans. In suspected Helicobacter pylori-associated disease, the noninvasive stool antigen or urea breath test is recommended. If patients fail to respond to treatment and antimicrobial resistance is suspected, gastric biopsy, gastric brushings, or gastric aspirate may be cultured to attempt to recover the organism for antimicrobial susceptibility testing to assess for resistance.
Multidrug regimens are required to attain successful cure of Helicobacter pylori infection. Antimicrobial resistance in Helicobacter pylori is increasing. Disease caused by Helicobacter pylori resistant to clarithromycin or metronidazole is associated with a greater incidence of treatment failure than disease caused by a susceptible strain.
The Clinical and Laboratory Standards Institute (CLSI) recommends agar dilution for Helicobacter pylori antimicrobial susceptibility testing. Amoxicillin, ciprofloxacin, clarithromycin, metronidazole and tetracycline are routinely tested. The only antimicrobial for which interpretive breakpoints have been defined by the CLSI is clarithromycin.
Recovery of Helicobacter pylori from gastric specimens for antimicrobial susceptibility testing of the organism. Amoxicillin, ciprofloxacin, clarithromycin, metronidazole and tetracycline are routinely tested.
A positive result provides definitive evidence of the presence of Helicobacter pylori.
Organisms may be detected in asymptomatic (colonized) individuals.
False-negative culture results may 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. Delays in specimen transportation will decrease recovery of the organism. Culture should be set up as soon as possible following specimen collection. Antimicrobial therapy may render the culture negative.
Due to Helicobacter pylori’s fastidious nature and slow-growth, it may take 7 days to recover the organism and up to an additional 21 days to perform antimicrobial susceptibility testing.
The only antimicrobial for which interpretive breakpoints have been defined by the Clinical and Laboratory Standards Institute is clarithromycin.
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. Lawson AJ: Chapter 54, Helicobacter. In Manual of Clinical Microbiology. 10th edition. Edited by J Versalovic. ASM Press. Washington DC, 2011, pp 900-915
2. Theel ES. Helicobacter pylori Infection: Test Utilization Strategies for Diagnosis. Mayo Medical Laboratories Communique 2013;38(6):1-8