FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam 2025 - Free NABP Practice Questions and Study Guide

Helicobacter pylori (H. pylori) is classified as a Gram-negative bacterium. This classification is based on the bacterium's cell wall structure, which contains a thinner peptidoglycan layer surrounded by an outer membrane, characteristic of Gram-negative organisms. When subjected to the Gram staining procedure, H. pylori does not retain the crystal violet stain and instead takes up the counterstain, which is consistent with Gram-negative bacteria.

While H. pylori is also considered facultative anaerobic, meaning it can grow in both the presence and absence of oxygen, this distinction is more relevant to its metabolic processes rather than defining its basic classification. Understanding the Gram-negative nature of H. pylori is crucial in contextualizing its pathophysiological role in conditions like peptic ulcers and gastritis, as well as in determining appropriate antibiotic treatments since Gram-negative bacteria often display different sensitivities compared to Gram-positive bacteria.