Understanding Neisseria: The Bacteria Behind Meningitis and Gonorrhea

 

Introduction of Genus Neisseria

Neisseria is a gram negative diplococci with adjacent sides concave, being typically kidney shaped.  Are non-spore-forming, No motile, relatively fragile, susceptible to temperature changes, drying, UV light, and other environmental conditions, Aerobic, Oxidase positive, most catalase positive, Fastidious, and requiring complex media for growth. Neisseria it is a large genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogen: N. meningitides- major cause of meningitis and N. gonorrhoeae- cause of gonorrhea. Are closely related, 70% DNA homology mostly Differentiated by a few laboratory tests and specific characteristics. Most importantly differentiated by clinical presentations of the diseases they cause: Meningococci typically are found in the URT and cause meningitis and Gonococci cause genital infections.

Major species of clinical importance

1. N. gonorrhoeae:

It is a Gram-negative coccus, 0.6 to 1.0 µm in diameter, usually seen in pairs, resemble a pair of kidney beans, Unencapsulated, Piliated, and Non motile. Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhea that can infect both males and females the bacterium infects warm moist areas of the body, including the eyes, throat, unus, cervix, and urethra. Gonorrhea is most commonly spread during sexual contact with an infected person, it can also spread from mother to child during birth if the mother is infected. Previous infection does not confer immunity a person who has been previously infected can become infected again by exposure to an infected person In babies, gonorrhea most commonly affects the eyes. It is called ophthalmia neonatorum. Men have 20% risk of getting the infection from a single act of vaginal intercourse with an infected woman, women have a 60-80% risk of getting the infection from a single act of vaginal intercourse with an infected man untreated gonorrhea can lead to significant complications such as infertility in men and women, pelvic inflammatory disease in women that spreads to the joint or heart valves.

Causes of N. gonorrhoe

Gonorrhea is caused by the bacterium Neisseria gonorrhea the bacteria are most often passed from one person to onother during sexual contact, including oral, anal, and vaginal intercourse.an infected mother may transmit gonorrhea to her newborn during childbirth.

Risk factors may include:

• Multiple sex partners

• Younger age

• Previous gonorrhea diagnosis

• Having other sexually transmitted infections

• A new sex partner

Symptoms

In many cases, symptoms may not appear. But if they do, they occur 2 to 14 days after exposure and may include:

In men

• Painful urination

• Pus-like discharge from the tip of the penis which may be yellow, white, beige or greenish

• Swelling or pain in the testicles or scrotum

• Swelling or redness at the opening of the penis

In women

• Increased vaginal discharge (watery, creamy, or slightly green)

• Painful sexual intercourse

• Painful or frequent urination

• Abdominal or pelvic pain

• Vaginal bleeding between periods heavier period

• Bleeding after intercourse

In both sexes:

Proctitis, pharyngitis, conjunctivitis, bacteremia which may lead to metastatic infection such as arthritis, endocarditis, meningitis, pyem& skin rashes.

Ophthalmia neonatorum (Purulent conjunctivitis) 

Nonvenereal gonococcal conjunctivitis in the newborn) } Results from direct infection during passage through infected birth canal. Characterized by a sticky discharge, Begin 2 to 5 days after birth. 1% silver nitrate eye drops (or ophthalmic preparations containing erythromycin or tetracycline) are used as a prophylactic agent.

Diagnosis

Specimens:  pus and secretions from the urethra, cervix, rectum, conjunctiva, or throat, for culture and smear.  blood culture in systemic illness  Gram-stained smears of urethral or endocervical exudate reveal many diplococci within pus cells.  Culture: on enriched selective medium (eg, modified Thayer- Martin medium) and incubated in 5% CO2, to avoid overgrowth by contaminants. Nucleic Acid Amplification Tests:  Serology: Serum and genital fluid contain IgG and IgA antibodies against gonococcal pili, outer membrane proteins, and LPS.

Treatment

•  Ceftriaxone, intramuscularly as a single dose.

•  doxycycline, orally twice a day for 7 days.

2. Neisseria meningitides:

It is a gram-negative bacterium that can cause meningitis and  other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. Identical in staining and morphological characteristics to N. gonorrhoeae  but N. meningitidis has capsule. It has 13 serogroups identified based on capsular polysaccharides (A, B, C, D, H, I, K, L, X, Y, Z, 29E, and W135).  Humans are the only known hosts.

General characteristics

• Gram stain: gram-negative diplococcus.

• Shape: kidney-bean shaped.

• Oxidase: positive.

• Catalase: positive.

• Capsule: polysaccharide capsule.

• Non-motile.

• Obligate aerobes.

• Non-spore forming.

• Oxygen need.

Virulence factors

• Capsule: protects from phagocytosis

• Pilli: mediates attachment to mucosal surfaces

• Endotoxin: causes septic shock and vascular damage

• IgA protease: cleaves secretory IgA, aiding mucosal colonization

How does the infection spreads?

• Coughing

• sneezing

• kissing

• respiratory droplets

symptoms of Neisseria meningitidis

• Sudden onset of fever

• Severe headache

• Stiff neck

• Vomiting

• Dizziness

• Fatigue and low energy

• Cold hands and feet

• Difficult breathing

Complications

• Sepsis

• Brain damage

• Hearing loss

• Organ failure

Diagnostic Laboratory Tests

Specimens: blood for culture, and CSF for smear and culture, Culture: CSF specimens are plated on "chocolate" agar and incubated at 37 °C in an atmosphere of 5% CO2 and A modified Thayer-Martin medium with antibiotics (vancomycin, colistin, amphotericin) oxidase +ve: a key test for identifying Neisseriae. Serology: antibodies to polysaccharides can be measured by latex agglutination. Immunity: group specific bactericidal antibodies in the serum is a Following colonization of the nasopharynx, protective humoral immunity develops against the same or closely related organisms of the same serogroup.

Treatment

Penicillin G is the drug of choice either chloramphenicol or a third- generation cephalosporin is  used in persons allergic to penicillins.

Epidemiology, Prevention, & Control

• Humans only natural hosts.

• Person-to-person transmission by aerosolization of respiratory tract secretions in crowded   conditions Close contact with infectious person (e.g., family members, day care centers, military barracks, prisons, and other institutional settings).

• Highest incidence in children younger than 5 years and particularly those younger than 1 year of age.

• 5% to 30% commonly colonize nasopharynx of healthy individuals.

• Vaccine for groups A, C, Y, and W-135 are the capsular polysaccharides 37.

Conclusion  

Neisseria meningitidis is a dangerous bacteria that causes meningitis and blood-borne infections. The disease begins suddenly, so recognizing early symptoms and getting medical care is life-saving. Hygiene and vaccination are the most effective ways to prevent the spread of this dangerous disease.