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Introduction to Laboratory Medicine Medical Microbiology :

Introduction to Laboratory Medicine Medical Microbiology Pyogenic Cocci 2 Neisseria Dr JWA Reuther

Neisseria Species Introduction:

Neisseria Species Introduction The Neisseria genus consists of aerobic, non-spore-forming Gram-negative coccobacilli which inhabit the mucous membranes of many animals (and humans). These non-motile microbes require a moist environment and warm temperatures (human body temperature range) to achieve optimum growth.

Neisseria Species Classification:

Neisseria Species Classification Currently divided into two groups on the basis of pigmentation and sugar metabolism. There is a possible third group, Branhamella catarhalis , which shows some relationships with groups 1 and 2 but differs in a number of features including the ability to hydrolyse tributyrin, reduce nitrate and produce DNAase.

Neisseria Species Classification:

Neisseria Species Classification Group 1 These strains are non-pigmented and form translucent colonies. They are generally asaccharolytic. The species include: N. cinerea N. gonorrhoeae N. gonorrhoeae subsp. kochii N. lactamica N. meningitidis N. polysaccharea

Neisseria Species Classification:

Neisseria Species Classification Group 2 These strains are yellow-pigmented and form opaque colonies. They are generally saccharolytic. The species include: N. mucosa, N. sicca N. Subflava the asaccharolytic species N. flavescens .

Neisseria Species Classification:

Neisseria Species Classification Group 3 The strains of the species Branhamella catarhalis are considered by some taxonomists to form a possible third group, due to relationships with both groups, but having distinct features.

Neisseria Species Culture:

Neisseria Species Culture Grows on Chocolate Agar at 37 o C in 6% Carbon Dioxide Selective Agar: Grows on New York City ( NYC) media - this is an enriched media containing antibiotics (vancomycin, colistin, nystatin, and trimethoprim) which permits the growth of pathogenic Neisseria but suppresses the growth of nonpathogenic Neisseria, Moraxella and other gram negative organisms

Neisseria Species Identification:

Neisseria Species Identification An important means of identification of Neisseria species is the oxidase test, for which all members test positive. Additionally, Neisseria grow well on chocolate agar containing antibiotics that inhibit growth of Gram-negative bacteria, Gram-positive bacteria, and moulds. (NYC Media). Characteristic fermentation patterns on solid sugar slopes.

Neisseria Species Sugar fermentations:

Neisseria Species Sugar fermentations Glucose Maltose Sucrose Lactose N.meningitidis   - - N.gonorrhoea  - - - N.sicca    - N.flavescens - - - - N.lactamica   -  B.catarrhalis - - - -

Neisseria Species Identification:

Neisseria Species Identification oxidase test - detects the presence of the enzyme cytochrome oxidase using a dye, tetramethyl-p-phenylenediamine dihydrochoride. The dye is colourless in the reduced state but purple in the oxidized state. A positive oxidase test is commonly used for presumptive identification of Neisseria species because these organisms contain large amounts of the enzyme, cytochrome oxidase.

Neisseria Species:

Neisseria Species The genus Neisseria contains a number of species which are normal flora and pathogens of humans and animals. The two most clinically significant members of the genus Neisseria are: N. gonorrhoeae and N. meningitidis .

Neisseria Species N.gonorrhoea:

Neisseria Species N.gonorrhoea N.gonorrhoea: Strains may infect the mucosal surfaces of urogenital sites (cervix, urethra, rectum) and the oro- and nasopharynx (throat), causing symptomatic or asymptomatic infections. Infections of the urogenital sites are more frequently symptomatic than asymptomatic; however, asymptomatic infections may occur. Gonococcal infections of the oro- and nasopharynx and the rectum may be asymptomatic more frequently than symptomatic.

Neisseria Species N.gonorrhoea:

Neisseria Species N.gonorrhoea Because investigations of sexual abuse may be initiated on the basis of a laboratory diagnosis of gonorrhoea, only definitive/confirmed identifications of N. gonorrhoeae should be accepted by a clinician. Such identifications should only be made only on the basis of identification of an isolate of N. gonorrhoeae in a standard culture. Isolates should be identified by at least two (2) tests that involve different principles (e.g., biochemical, serological, or nucleic acid probe culture confirmation tests) and take into account additional tests that should be performed to compensate for problems known to be associated with the primary confirmation tests. Isolates should be preserved in case additional or repeated testing is needed.

Neisseria Species:

Neisseria Species Neisseria meningitidis: Strains may be carried as normal flora in the throat. Under some circumstances. N. meningitidis may also be pathogenic, causing sporadic cases or epidemics of meningitis. Between 3% and 30% of healthy persons in non-epidemic geographic areas may be asymptomatic carriers of N. meningitidis i.e., meningococci have colonized their throats without causing disease. The carrier state may persist for many months.

Neisseria Species N. meningitidis :

Neisseria Species N. meningitidis N. meningitidis causes epidemic meningitis in many parts of the world such as Sub-Saharan Africa. Certain types of N. meningitidis are usually associated with meningitis. Of a total of 13 serogroups of N. meningitidis , strains belonging to the serogroups A, B, C, and W-135 have most frequently been associated with epidemics. Group A strains have been associated with most epidemics, whereas group B, C, and W-135 strains have caused sporadic epidemics.

Neisseria Species:

Neisseria Species PATHOGENICITY: Acute disease characterized by sudden onset with fever, intense headache, nausea and often vomiting, stiff neck, and frequently a petechial rash with pink macules; delirium and coma. Early diagnosis and modern therapy have reduced case fatality rate from 50% to less than 10%. May be asymptomatic or with only local symptoms, 10% of patients who recover have permanent neurologic disability, limb loss, and hearing loss. Invasive with septicaemia or meningitis; death rate is high in fulminating meningococcaemia. Infection usually causes sub-clinical mucosal infections; carrier prevalence of 25% or greater may exist without cases of meningitis

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