Fastidiosos

Neisseria meningitidis

Gram-negative diplococci, often intracellular in CSF

Identification & Growth

Identification

Oxidase-positive; ferments both glucose and maltose
Serogrouping by latex agglutination (A, B, C, W, Y)

Growth Conditions

Blood and chocolate agar, 35 °C with CO₂, 18–24 h
CSF samples should not be refrigerated

Clinical Significance

Meningitis and meningococcemia — a clinical and public health emergency

Intrinsic Resistance

Vancomycin, clindamycin, linezolid, trimethoprim

Bench Alerts

Immediate mandatory notification and contact prophylaxis
Handle inside a class II biological safety cabinet
Disk diffusion on MH-F agar; test penicillin by MIC

Clinical Notes

Clinical presentations

Causes acute bacterial meningitis with sudden onset of fever, headache, neck stiffness, and altered mental status.
Meningococcemia can rapidly progress to septic shock, disseminated intravascular coagulation, and purpura fulminans.
Petechial or purpuric rash is a warning sign requiring immediate antimicrobial treatment without awaiting laboratory confirmation.

Specimens and collection

Cerebrospinal fluid and blood cultures should be collected as quickly as possible, without delaying the start of empiric antibiotic therapy.
Petechial lesion aspirate can be examined directly and cultured in selected cases.
Molecular detection (PCR) in CSF is particularly useful when antibiotics were already administered before collection.

Epidemiology and at-risk populations

Outbreaks occur in close-contact settings such as university dormitories, military barracks, and the meningitis belt in sub-Saharan Africa.
Terminal complement deficiency (C5-C9) and asplenia predispose to recurrent or severe meningococcal disease.
Conjugate vaccination against serogroups A, C, W, Y and serogroup B vaccines have reduced invasive disease incidence in vaccinated populations.

Resistance and therapeutic implications

Reduced penicillin susceptibility has been reported in some regions, reinforcing the use of third-generation cephalosporins in empiric treatment.
Ciprofloxacin or rifampin are used for close-contact chemoprophylaxis, with fluoroquinolone resistance reported sporadically.
Isolates should have confirmed susceptibility before de-escalating from cephalosporin to penicillin for definitive therapy.

Bench and reporting notes

Intracellular and extracellular gram-negative diplococci in CSF on Gram stain are highly suggestive of meningococcal meningitis.
Serogroup determination is essential for epidemiologic surveillance and defining the need for extended chemoprophylaxis.
Suspected or confirmed cases require immediate notification to public health authorities due to outbreak risk.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Neisseria meningitidis in the lab?

Neisseria meningitidis is identified through oxidase-positive; ferments both glucose and maltose, serogrouping by latex agglutination (a, b, c, w, y).

What are the intrinsic resistances of Neisseria meningitidis?

This organism is naturally resistant to vancomycin, clindamycin, linezolid, trimethoprim. These drugs should not be reported as susceptible.

Where is Neisseria meningitidis commonly found?

It is typically associated with meningitis and meningococcemia — a clinical and public health emergency.

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