[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › Other Gram-negative rods [Microbiology](https://durgical.com/en/microbiology/) · [Bacteria](https://durgical.com/en/microbiology/#d-bacteria) # Other Gram-negative rods - Bacteria Curved rods, coccobacilli and non-fermenters: H. pylori, Vibrio, Pseudomonas, Haemophilus, Bordetella, Legionella and the zoonoses. Updated 2026-11-01 ## What they are A working group of Gram-negative rods that are not Enterobacterales. It holds the curved gut rods (Vibrio, Campylobacter, Helicobacter), the hospital non-fermenters (Pseudomonas, Acinetobacter), the respiratory coccobacilli (Haemophilus, Bordetella, Legionella) and the zoonotic bacteria (Bartonella, Brucella, Francisella). Gram-variable Gardnerella sits here for its role in vaginosis. ## What they share - Most are oxidase-positive (Vibrio, Campylobacter, Helicobacter, Pseudomonas) - Several need special media: chocolate agar with factors X and V (Haemophilus), BCYE (Legionella), Bordet-Gengou or Regan-Lowe (Bordetella), TCBS (Vibrio) - The zoonoses strike people who work with animals or animal products - Pseudomonas and Acinetobacter: multidrug-resistant in intensive care units ## Key points - Urea in the breath or biopsy: Helicobacter pylori makes urease. - TCBS agar with yellow colonies: Vibrio cholerae. - Haemophilus needs factor X (hemin) and factor V (NAD). - Legionella: urinary antigen, BCYE agar, pneumonia with hyponatremia. - Pseudomonas: oxidase-positive, green pigment, grape-like smell. ## Microorganisms in this group - [**Helicobacter pylori** A bacterium that lives in the stomach, usually from childhood. It causes gastritis and ulcers and raises the risk of stomach cancer. Exam priority: high](https://durgical.com/en/microbiology/helicobacter-pylori/) - [**Vibrio cholerae** A bacterium in contaminated water that causes cholera: watery diarrhea so heavy it can kill by dehydration within hours. Exam priority: high](https://durgical.com/en/microbiology/vibrio-cholerae/) - [**Campylobacter jejuni** A bacterium from undercooked chicken that causes diarrhea, often bloody; rarely it is followed by paralysis (Guillain-Barré). Exam priority: medium](https://durgical.com/en/microbiology/campylobacter-jejuni/) - [**Pseudomonas aeruginosa** A water and soil bacterium that attacks hospital, burn and cystic fibrosis patients, and resists many antibiotics. Exam priority: medium](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/) - [**Acinetobacter baumannii** An intensive care unit bacterium that survives on dry surfaces and resists nearly every antibiotic. Exam priority: medium](https://durgical.com/en/microbiology/acinetobacter-baumannii/) - [**Haemophilus influenzae** A throat bacterium. Type b caused meningitis and epiglottitis in children before the vaccine; capsule-free strains cause ear and sinus infections. Exam priority: medium](https://durgical.com/en/microbiology/haemophilus-influenzae/) - [**Bordetella pertussis** The whooping cough bacterium: coughing fits that last weeks. In babies under one year it can cause apnea and death. Exam priority: medium](https://durgical.com/en/microbiology/bordetella-pertussis/) - [**Legionella pneumophila** A bacterium in water from cooling towers, showers and hot tubs. Inhaled, it causes severe pneumonia (Legionnaires' disease) or a mild fever. Exam priority: medium](https://durgical.com/en/microbiology/legionella-pneumophila/) - [**Bartonella** Bacteria carried by cats, sand flies and lice. B. henselae causes cat scratch disease; B. bacilliformis causes Andean Carrión disease. Exam priority: medium](https://durgical.com/en/microbiology/bartonella/) - [**Brucella** Livestock bacteria that reach people through unpasteurized milk or cheese or contact with animals: a fever that comes and goes. For completeness](https://durgical.com/en/microbiology/brucella/) - [**Francisella tularensis** A bacterium of rabbits, hares and rodents spread by ticks, deer flies, contact or air; it causes tularemia and is very infectious in the lab. For completeness](https://durgical.com/en/microbiology/francisella-tularensis/) - [**Gardnerella vaginalis** A bacterium that overgrows when vaginal lactobacilli are lost and causes bacterial vaginosis: gray discharge with a fishy smell. For completeness](https://durgical.com/en/microbiology/gardnerella-vaginalis/) ## Test yourself Think of the answer, then tap the question to see it. ## Which curved Gram-negative rods are oxidase-positive and cause diarrhea or gastritis? Vibrio, Campylobacter and Helicobacter. ## Which growth factors does Haemophilus influenzae need? Factor X (hemin) and factor V (NAD), both supplied by chocolate agar. ## On which medium does Legionella grow? Buffered charcoal yeast extract (BCYE) agar with cysteine and iron. ## Which Gram-negative non-fermenter is a classic cause of ventilator-associated pneumonia? Pseudomonas aeruginosa (Acinetobacter baumannii as well). [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/groups/other-gram-negative-rods/) [← All of microbiology](https://durgical.com/en/microbiology/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [About Pseudomonas aeruginosa](https://www.cdc.gov/pseudomonas-aeruginosa/about/index.html) (CDC, 2025); [Chapter 8: Haemophilus influenzae](https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-8-haemophilus-influenzae.html) (CDC, 2024); [Cholera](https://www.who.int/news-room/fact-sheets/detail/cholera) (WHO, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/groups/other-gram-negative-rods/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/groups/other-gram-negative-rods/