Neisseria

Neisseriaceae

This family includes the genera Neisseria and Moraxella .

General characteristic 

1- All Neisseria are gram negative diplococcic . 2- On microscopy the cocci are seen as pairs with concave adjacent side (bean - shaped) or kidney shape , tetrads , short chain and clusters , but all show the characteristic pairing.

3- Non – motile .4- Non spore forming5- ranging from 0.6-1.0 µm in diameter.6- member of this genus grow optimally at 36-39C,although non –pathogenic species can grow at temperatures below 24C.


7- Non – capsulated (but in some species the cell may surrounded by small capsule).8- Neisseria contains tow pathogenic species and a number of others that are commonly found in the normal flora of the upper respiratory tract .9- The pathogenic species are obligate human parasites and quite fastidious in their growth requirements on artificial media especially on initial isolation from clinical specimens .

The genus Neisseria contains tow pathogenic species and a number of others are commonly found in the normal flora of the upper respiratory tract , the tow medically important species are :-

Meningococci))1- N. meningitides caused :- Meningities pneumonia , arthritis pericarditis septicemia . Gonococci))2- N. gonorrboeae caused : Gonorrhea Genitourinary tract infection arthristis conjunctivitis

1- N. gonorrhoeae:-

The human urogenital tract is the usual habitat ,oral nasopharyngeal and rectal carriage in healthy individuals is not uncommon. Spread is by both homosexual heterosexual intercourse or intimate contact.


gram-negative diplococci in presence of polymorphonuclear leukocytes (PMN’s) intracellular seen microscopically in urethral discharge from men and the cervix in women. Specimen are usually inoculated on an enriched media (chocolate agar normally) and incubated under 5-10% of CO2 , production of acid from glucose but not from maltose and sucrose.

Neisseria gonorrhoeae in Urethral discharge

2- N. meningitides:- 
The main reservoir is the nasopharynx of normal people (10-25)%. Droplet spread is the most common transmission mode . Samples from nasopharyngeal discharge ,cerebrospinal fluid or blood .

Large numbers (e.g., >107cells/ml) gram negative (bean shape) and polymorphonuclear leukocytes diplococci (PMN’s) can be seen microscopically in cerebrospinal fluid (CSF)This organism resembles the gonococcus but N. menigitidis cells are capsulated ,Identified by the carbohydrate utilization test). Produce acid from oxidation of glucose and maltose.

Neisseria meningitidis in Cerebrospinal Fluid

Lab diagnosis

Although T.M. medium widely used in many laboratories , 3-10% of gonococcal inhibited by vancomycin Use of lincomycin as selective agent avoids the problem of vancomycin sensitivity .

:(2-CTA (Cystein Trypticase Agar this medium is used to test carbohydrates Utilization by Neisseria with the production of acetate that lower the pH of the media and change the color in the media from pink to yellow. So CTA is used for determination of fastidious organisms including Neisseria , this media contain phenol red , cystein , sodium sulfite , NaCl, Trypticase the carbohydrates used are added in 1% con. To the sterile medium .


Commensal species of Neisseria 
Are common in the oral cavity , nose , and some time in the female genital tract . The three main species are : N.subflava N. mucosa N.sicca

The main difference between these and the pathogenic :Neisseria is 1- the ability of the commensally to grow on ordinary agar at room temp. in the absence of CO2 supplements 2-pathogenic Neisseriarae intercellular while non pathogenic species are extracellular 3-Pathogenic Neisseria are small and mucoid , while other species tend to be large ..

Moraxella :- 

They are commensal of the human respiratory tractand are recognized opportunistic pathogens causing meningitis ,endocarditis and otitis media The genus Moraxella are gram negative cocci or short rods , they typically occurs in pairs . Strict aerobes , usually catalase positive , donot ferment sugar , non capsulated , non motile , oxidase positive and donot produce indol or H2S. M. catarrhalis was formely classified in the genus Neisseria.

Danase

Oxidase
Acid production G M S
Growth on simple media in air
Growth on enrichment media in CO2
Pathhogenicity
Name of organism
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Gonorrhea
N. gonorrhoeae
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Menigitdis
N. menigitidis
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Normal flora in respiratory tract
N. sicca
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Normal flora in upper respiratory tract
N. flarescens
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Normal flora in upper respiratory tract
M. catarrhalis


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