Genus Neisseria عملي

Genus Neisseria

Family Neisseriaceae

The family Neisseriaceae

The family Neisseriaceae includes the genera Neisseria, Kingella, Eikenella, Simonsiella, and Alysiella.

Genus Neisseria

Members found in human include N. gonorrhoea N. meningitidis N lactamica, N sicca, N. subflava, N. mucosa, N. polysaccharea, N. elongata. Most of these are part of the normal flora. N. gonorrhoea is always considered pathogen regardless the site of isolation. N. meningitides cause significant sever disease but may colonize the nasopharynx and oropharynx.

This genus contains two pathogenic spp.

1- Neisseria meningitidis (meningeococcus) is the etiologic agent of pyogenic meningococcal meningitis, transmitted by respiratory droplets, meningococcal meningitis must be treated early and aggressively to avoid death. the natural habitat of the meningococcus is the human nasopharynx. It is the only bacterium that is capable of generating epidemic outbreaks of meningitis.

2- Neisseria gonorrhoeae (gonococcus). It is the cause of gonorrhea. This sexually transmitted disease is not fatal, but it can lead to blockages of the reproductive tubes resulting in sterility. Gonococci attack mucous membranes of the genitourinary tract, eye, rectum, and throat, producing acute suppuration, tissue invasion; this is followed by chronic inflammation and fibrosis.

In males, there is usually urethritis, with yellow, creamy pus and painful urination, sometimes leading to urethral strictures. Urethral infection in men can be asymptomatic. In females, the primary infection is in the endocervix and extends to the urethra and vagina, giving rise to mucopurulent discharge. It may then progress to the uterine tubes, causing salpingitis, fibrosis, and obliteration of the tubes. Infertility occurs in 20% of women with gonococcal salpingitis.

Specimen collection

N.gonorrhoea: a. genital secretions, in males is from the urethra and in females endocervix, b.rectum,c. pharynx, d.joint fluid. N.meningetidis: CSF, blood, nasopharynx, sputum. Direct plating of the specimen gives optimal results.

Microscopical appearance

Gram negative cocci, arranged in pairs, the cocci are kidney shape with flat or concave opposing sides, non motile, non sporing. The pathogenic spp mostly appear intracellular (in pus cells) and sometimes extracellular, while the non pathogenic spp are usually extracellular.

Cultural characteristics

Aerobic, pathogenic spp. Require 5-10% CO2 for primary isolation(Capnophillic spp). The pathogenic spp are fastidious so they need enriched media. The non pathogenic can grow on simple media The colonies are small, greyish, transparent, no hemolysis on blood agar.

Media used for isolation of Neisseria

1. blood agar 2. Chocolate agar 3. selective media Theyer-Martin Modified Theyer- Martin Martin Lewis (ML). New York City (NYC) media.

Candle jar

Biochemical activities
1- Oxidase test: All spp produce oxidase enzyme. Freshly prepared 5% solution of oxidase reagent (tetramethyl-p-phenylene diamine hydrochloride) poured on filter paper and colony added, positive reaction indicated by purple colour.

2- suger fermentation

Used to differentiate pathgenic spp from commensals, the medium used contains serum to enhance the growth of pathogenic spp. produce acid from CHO oxidatively . Positive: yellow colour Negative: red colour

The M.O

Glucose
Maltose
Sucrose
Lactose
N. gonorrohoea
+
-
-
-
N. meningitidis
+
+
-
-
N mucosa
+
+
+
-
Moraxella
-
-
-
-

Gonococci oxidize only glucose

N.M oxidises glucose and maltose

N.mucosa oxidises glucose maltose and sucrose