[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Gram-negative cocci](https://durgical.com/en/microbiology/groups/gram-negative-cocci/) › Neisseria meningitidis [Microbiology](https://durgical.com/en/microbiology/) · [Gram-negative cocci](https://durgical.com/en/microbiology/groups/gram-negative-cocci/) # Neisseria meningitidis - Bacterium - Gram-negative - Droplet - Exam priority: high A throat bacterium that can cause meningitis and a bloodstream infection with skin spots that worsens within hours. Updated 2026-11-01 Also called: meningococcus ## Key points - Fever, stiff neck and non-blanching purpura: meningococcus until proven otherwise. - Terminal complement deficiency (C5 to C9) or eculizumab use: recurrent meningococcal infections. - Bilateral adrenal hemorrhage with shock: Waterhouse-Friderichsen syndrome. - NCLEX: droplet precautions until 24 hours of antibiotics; private room and surgical mask. - Close contacts get chemoprophylaxis even when well. ## At a glance **Gram** Gram-negative **Shape** Coffee-bean diplococcus **Oxygen** Aerobic **Family** Neisseriaceae **Stain** Gram: red diplococci, often inside neutrophils in CSF ## Morphology - Gram-negative diplococci with flat facing sides - Polysaccharide capsule defines the serogroups (A, B, C, W, X, Y) - Oxidase-positive; ferments glucose and maltose - Grows on chocolate agar and Thayer-Martin ## Transmission - Respiratory droplets and throat secretions during close or long contact (household, kissing, dormitories, barracks) - Many healthy people carry it in the nasopharynx without illness - Droplet precautions until 24 hours after an effective antibiotic is started **Reservoir:** Humans only (nasopharynx) ### Isolation precautions What the care team adds to standard precautions. **Droplet** Surgical mask within about a metre; single room. ## Virulence factors - Capsule: blocks phagocytosis and complement lysis - Lipooligosaccharide (LOS): endotoxin that drives shock, disseminated intravascular coagulation and vessel damage - Pili and membrane proteins: attachment to nasopharyngeal epithelium - IgA protease: cleaves mucosal IgA - Sheds endotoxin-rich membrane blebs, which explains how severe the sepsis can be ## Diseases it causes - Acute bacterial meningitis, mainly in infants, adolescents and young adults [Bacterial meningitis →](https://durgical.com/en/conditions/bacterial-meningitis/) - Meningococcemia: sepsis with petechiae and purpura that do not blanch [Meningococcal disease (meningococcemia) →](https://durgical.com/en/conditions/meningococcal-disease/) - Septic shock with disseminated intravascular coagulation and adrenal hemorrhage (Waterhouse-Friderichsen syndrome) [Sepsis and septic shock →](https://durgical.com/en/conditions/sepsis-and-septic-shock/) ## Clinical picture - Fever, headache, neck stiffness, photophobia and confusion - A non-blanching petechial or purpuric rash is a red flag - Infants: irritability, poor feeding, bulging fontanelle - Can go from mild symptoms to shock within hours ## Diagnosis - Lumbar puncture: cloudy CSF with neutrophils, low glucose and high protein; it must not delay antibiotics - CSF Gram stain: Gram-negative diplococci - Blood and CSF culture on chocolate agar (reference test) - PCR on blood or CSF, useful after antibiotics have been given ## Treatment A medical emergency: immediate intravenous antibiotic with a third-generation cephalosporin (ceftriaxone or cefotaxime); penicillin when the strain is susceptible. Strains with reduced penicillin susceptibility have been reported. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Ceftriaxone](https://durgical.com/en/pharmacology/ceftriaxone/) - [Benzylpenicillin (penicillin G)](https://durgical.com/en/pharmacology/benzylpenicillin/) - [Rifampicin](https://durgical.com/en/pharmacology/rifampicin/) - [Ciprofloxacin](https://durgical.com/en/pharmacology/ciprofloxacin/) ## Prevention - Conjugate vaccines against serogroups A, C, W and Y, and protein-based vaccines against serogroup B - Chemoprophylaxis for close contacts (rifampicin, ciprofloxacin or ceftriaxone), ideally within 24 hours - Droplet precautions for health workers - Testing for complement deficiency after repeated infections **Vaccine:** Conjugate vaccines (ACWY, and the pentavalent ACWYX) and serogroup B vaccines exist. In Colombia it is not part of the routine PAI schedule for all children; it is used for risk groups and travelers. ## In Colombia Bacterial meningitis and meningococcal disease are mandatory notifiable events in SIVIGILA (INS); each case triggers contact tracing and prophylaxis. ## Memory aid "The meningococcus has malt in its coffee": the coffee-bean diplococcus that ferments maltose as well as glucose; the gonococcus sticks to glucose. ## Test yourself Think of the answer, then tap the question to see it. ## A teenager has fever, neck stiffness and non-blanching petechiae. Which isolation precaution applies? Droplet precautions (on top of standard) until 24 hours after an effective antibiotic is started. ## Which immune defect predisposes to repeated meningococcal infections? Deficiency of the terminal complement components (C5 to C9), or C5 blockade with eculizumab. ## What is Waterhouse-Friderichsen syndrome? Shock with bilateral adrenal hemorrhage and acute adrenal failure during fulminant sepsis, classically meningococcal. ## Which N. meningitidis component is the basis of its conjugate vaccines? The capsular polysaccharide, linked to a carrier protein. ## Which antibiotics are used as chemoprophylaxis for contacts? Rifampicin, ciprofloxacin or ceftriaxone. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/neisseria-meningitidis/) ## Related - [Neisseria gonorrhoeae](https://durgical.com/en/microbiology/neisseria-gonorrhoeae/) - [Haemophilus influenzae](https://durgical.com/en/microbiology/haemophilus-influenzae/) ## Related conditions - [Bacterial meningitis](https://durgical.com/en/conditions/bacterial-meningitis/) - [Meningococcal disease (meningococcemia)](https://durgical.com/en/conditions/meningococcal-disease/) - [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. **Contact** Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing. **Droplet** Surgical mask within about a metre; single room. **Airborne** N95 respirator and a negative-pressure room. [← Back to the group: Gram-negative cocci](https://durgical.com/en/microbiology/groups/gram-negative-cocci/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Chapter 14: Meningococcal Disease](https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-14-meningococcal-disease.html) (CDC, 2024); [Meningitis](https://www.who.int/news-room/fact-sheets/detail/meningitis) (WHO, 2026); [About Meningococcal Disease](https://www.cdc.gov/meningococcal/about/index.html) (CDC, 2026); [Fichas y Protocolos](https://www.ins.gov.co/buscador-eventos/Paginas/Fichas-y-Protocolos.aspx) (Instituto Nacional de Salud (INS), Colombia, 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/neisseria-meningitidis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/neisseria-meningitidis/