Neisseria meningitidis vs Neisseria gonorrhoeae- 32 Differences

Neisseria meningitidis and Neisseria gonorrhoeae are two closely related species of bacteria that belong to the genus Neisseria. They are Gram-negative, oxidase-positive, aerobic diplococci that are human-specific pathogens. However, they have different clinical manifestations and niche preferences.

Neisseria meningitidis and Neisseria gonorrhoeae are both Gram-negative bacteria that belong to the genus Neisseria. They are diplococci, non-sporing, non-motile and oxidase positive. They can cause different types of infections in humans, such as meningitis, gonorrhea, urethritis, conjunctivitis and sepsis. However, they can be differentiated on the following grounds:

1. Common name:
   • Neisseria gonorrhoeae: Gonococcus
   • Neisseria meningitidis: Meningococcus
2. Capsule:
   • Neisseria gonorrhoeae: Absent
   • Neisseria meningitidis: Present and anti-phagocytic
3. Pili:
   • Neisseria gonorrhoeae: Usually one retracting pilus per cell
   • Neisseria meningitidis: Usually four retracting pili per cell
4. Plasmids:
   • Neisseria gonorrhoeae: Commonly present and may code for drug resistance
   • Neisseria meningitidis: Rarely present
5. Cell morphology:
   • Neisseria gonorrhoeae: Kidney-shaped with concave apposing ends
   • Neisseria meningitidis: Semicircular with flat apposing ends
6. Growth on blood agar:
   • Neisseria gonorrhoeae: Less well than N. meningitidis
   • Neisseria meningitidis: Well and may show hemolysis
7. Culture medium:
   • Neisseria gonorrhoeae: Requires selective media with antimicrobials to inhibit other bacteria
   • Neisseria meningitidis: Can grow on non-selective media such as blood agar or chocolate agar
8. Growth rate:
   • Neisseria gonorrhoeae: Slower than N. meningitidis
   • Neisseria meningitidis: Faster than N. gonorrhoeae
9. Fastidiousness:
   • Neisseria gonorrhoeae: More fastidious than N. meningitidis
   • Neisseria meningitidis: Less fastidious than N. gonorrhoeae
10. Colony morphology:
    • Neisseria gonorrhoeae: Smooth, round, moist, uniform grey/brown colonies with a greenish color underneath and irregular margins on primary isolation medium
    • Neisseria meningitidis: Smooth, round, moist, uniform large grey/brown colonies with a glistening surface and entire edges
11. Sugar fermentation:
    • Neisseria gonorrhoeae: Produces acid from glucose only
    • Neisseria meningitidis: Produces acid from glucose and maltose
12. Nitrite reduction:
    • Neisseria gonorrhoeae: Does not reduce nitrites
    • Neisseria meningitidis: Can reduce nitrites in low concentrations
13. Autolysis:
    • Neisseria gonorrhoeae: May autolyse
    • Neisseria meningitidis: Autolyse

Both Neisseria gonorrhoeae and Neisseria meningitidis are gram-negative diplococci that can be found inside or outside the host cells. However, they differ in their intracellular and extracellular forms.

Neisseria gonorrhoeae is mainly an intracellular pathogen that infects the mucosal epithelial cells of the urogenital tract, the rectum, the pharynx, and the conjunctiva. It can also invade the submucosal tissues and cause inflammation and damage. Neisseria gonorrhoeae can survive and multiply within neutrophils, which are a type of white blood cell that normally kill bacteria. This allows the bacteria to evade the immune system and spread to other sites of infection.

Neisseria meningitidis is mainly an extracellular pathogen that colonizes the nasopharynx of asymptomatic carriers. It can also cross the mucosal barrier and enter the bloodstream, where it can cause septicemia (blood poisoning) and meningitis (inflammation of the membranes covering the brain and spinal cord). Neisseria meningitidis can also attach to the endothelial cells that line the blood vessels and cause damage to them. This can result in bleeding, clotting, and shock.

The intracellular and extracellular forms of Neisseria gonorrhoeae and Neisseria meningitidis have different characteristics that help them adapt to their respective environments. For example, Neisseria gonorrhoeae has a higher resistance to oxidative stress than Neisseria meningitidis, which helps it survive inside neutrophils. On the other hand, Neisseria meningitidis has a higher ability to produce polysaccharide capsules than Neisseria gonorrhoeae, which helps it resist phagocytosis (engulfment by immune cells) and complement-mediated killing (a part of the immune system that destroys bacteria).

The intracellular and extracellular forms of Neisseria gonorrhoeae and Neisseria meningitidis are important for their pathogenesis and diagnosis. For example, intracellular Neisseria gonorrhoeae can be detected by microscopy or culture of urethral or cervical swabs. Extracellular Neisseria meningitidis can be detected by blood culture or cerebrospinal fluid analysis.

Neisseria meningitidis and Neisseria gonorrhoeae are both gram-negative diplococci that grow on chocolate agar and Thayer-Martin medium. However, they have different colony morphology on these media.

On chocolate agar, Neisseria meningitidis forms small, round, convex, smooth, moist, and translucent colonies that are usually surrounded by a narrow zone of hemolysis. The colonies may vary in color from white to gray to yellowish depending on the strain and the medium. Some strains may produce a brown pigment.

On chocolate agar, Neisseria gonorrhoeae forms small, round, flat, opaque, and mucoid colonies that are usually non-hemolytic. The colonies may have a greenish or yellowish tint depending on the strain and the medium. Some strains may produce a red pigment.

On Thayer-Martin medium, which is a selective medium that inhibits the growth of most other bacteria, Neisseria meningitidis and Neisseria gonorrhoeae can be differentiated by their susceptibility to antibiotics. Neisseria meningitidis is sensitive to vancomycin and colistin, while Neisseria gonorrhoeae is resistant to both. Therefore, Neisseria meningitidis grows as small colonies on Thayer-Martin medium with vancomycin and colistin (VCNT), while Neisseria gonorrhoeae grows as large colonies on Thayer-Martin medium without vancomycin and colistin (NT).

Both Neisseria meningitidis and Neisseria gonorrhoeae can cause systemic disease, which means that the bacteria can spread through the bloodstream and affect various organs and tissues. However, the frequency and severity of systemic disease are different for the two species.

Neisseria meningitidis is a major cause of meningitis, which is an infection of the meninges, the protective tissue of the brain and spinal cord. Meningitis can cause fever, headache, stiff neck, confusion, seizures, and sometimes death. Meningitis is a medical emergency that requires prompt diagnosis and treatment. Neisseria meningitidis can also cause meningococcemia, which is a life-threatening sepsis that can lead to shock, organ failure, and skin rash. Meningococcal disease can affect anyone, but it is more common in children under 5 years old and young adults under 20 years old. Vaccination is available for some types of Neisseria meningitidis and can prevent meningococcal disease.

Neisseria gonorrhoeae is a sexually transmitted infection (STI) that usually affects the urethra, cervix, rectum, or throat. It can cause discharge, pain, bleeding, and infertility if left untreated. In some cases, Neisseria gonorrhoeae can spread to the bloodstream and cause disseminated gonococcal infection (DGI), which can manifest as fever, joint pain, swelling, skin rash, or eye infection. DGI is more common in women than in men and can occur at any age. Treatment for gonorrhea is effective, but many cases go undetected due to asymptomatic infections or lack of access to sexual healthcare. Prevention of gonorrhea includes using condoms or other barrier methods during sexual intercourse and avoiding contact with infected people.

In summary, both Neisseria meningitidis and Neisseria gonorrhoeae have the ability to cause systemic disease, but they differ in their frequency, severity, risk factors, diagnosis, treatment, and prevention. Meningococcal disease is more serious and potentially fatal than DGI and requires urgent medical attention. Gonorrhea is more common and treatable than meningococcal disease but can have long-term complications if not diagnosed and treated early. Both diseases can be prevented by vaccination or safe sexual practices.

Neisseria gonorrhoeae and Neisseria meningitidis are both gram-negative diplococci that belong to the family Neisseriaceae. They share some common biochemical reactions, such as oxidase-positive, catalase-positive, and glucose-fermenting. However, they differ in other aspects, such as:

• Neisseria gonorrhoeae is maltose-nonfermenting, while Neisseria meningitidis is maltose-fermenting.
• Neisseria gonorrhoeae is DNase-positive, while Neisseria meningitidis is DNase-negative.
• Neisseria gonorrhoeae is nitrate-reducing, while Neisseria meningitidis is nitrate-nonreducing.
• Neisseria gonorrhoeae is beta-lactamase-producing, while Neisseria meningitidis is beta-lactamase-nonproducing.

Neisseria gonorrhoeae and Neisseria meningitidis also have different antigenic properties, such as:

• Neisseria gonorrhoeae has protein I (Por) and protein III (Opa) as major outer membrane proteins, while Neisseria meningitidis has protein II (PorA and PorB) and protein III (Rmp) as major outer membrane proteins.
• Neisseria gonorrhoeae has lipooligosaccharide (LOS) as the main surface antigen, while Neisseria meningitidis has polysaccharide capsule as the main surface antigen.
• Neisseria gonorrhoeae has multiple serogroups based on the variation of LOS, while Neisseria meningitidis has 12 serogroups based on the variation of capsule. The most common serogroups of Neisseria meningitidis that cause invasive disease are A, B, C, W, X, and Y.

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