''Neisseria cinerea'' is a commensal species grouped with the

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

, oxidase-positive, and catalase-positive diplococci. It was first classified as ''Micrococcus cinereus'' by

Alexander von Lingelsheim Alexander von Lingelsheim (27 September 1874, in Arolsen – 5 March 1937, in Breslau) was a German botanist and pharmacist. He studied natural sciences at the University of Breslau, and for many years he worked as an assistant in its botanica ...

in 1906. Using DNA hybridization, ''N. cinerea'' exhibits 50% similarity to '' Neisseria gonorrhoeae''.

Classification

''Neisseria cinerea'' has been formerly classified as many other organisms, including ''

Moraxella catarrhalis ''Moraxella catarrhalis'' is a fastidious, nonmotile, Gram-negative, aerobic, oxidase-positive diplococcus that can cause infections of the respiratory system, middle ear, eye, central nervous system, and joints of humans. It causes the inf ...

'' and ''Neisseria pseudocatarrhalis''. It is often mistaken for ''

N. gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection gon ...

'' with which it shares morphological and biochemical traits. Both are isolated from similar infections, including endocervical and rectal infections, neonatal

conjunctivitis Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. The ...

, and lymphadenitis.''N. cinerea'' has even been isolated on gonococcal selective media specifically made to isolate ''

''.

Colony morphology

One important difference between ''N. cinerea'' and ''N. gonorrhoeae'' is that ''N. cinerea'' is slightly more pigmented and exhibits a golden-brown rather than a pinkish-brown pigmentation. The average diameter of ''N. cinerea'' colonies varies, but stays around 1–2 mm. The colonies are convex, translucent, and glistening. No change occurs in the color of the media used to isolate ''N. cinerea'' before or after staining with

Lugol's iodine Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxicos ...

Biochemical processes

''Neisseria cinerea'' can produce acid from

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

like ''N. gonorrhoeae'', but it will then oxidize the acid to

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

. Although it can break down glucose, it is unable to use

or other carbohydrates for energy, making it asaccharolytic. In addition, ''N. cinerea'' will react in coagglutination serologic tests and, like ''N. gonorrhoeae'', it produces the enzyme hydroxyprolylaminopeptidase.''N. cinerea'' does not reduce nitrate, but it does reduce nitrite. Proline, arginine,

cystine Cystine is the oxidized derivative of the amino acid cysteine and has the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is poorly soluble in water. As a residue in proteins, cystine serves two functions: a site of redox reactions and a mec ...

, and cysteine are required for its growth. ''N. cinerea'' does not react with antigonococcal protein I monoclonal antibodies and does not produce

immunoglobulin A Immunoglobulin A (Ig A, also referred to as sIgA in its secretory form) is an antibody that plays a role in the immune function of mucous membranes. The amount of IgA produced in association with mucosal membranes is greater than all other typ ...

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...

, unlike ''N. gonorrhoeae''. Also unlike ''N. gonorrhoeae'', ''N. cinerea'' is not resistant to the antibiotic

colistin Colistin, also known as polymyxin E, is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia. These may involve bacteria such as ''Pseudomonas aeruginosa'', '' Klebsiella ...

, and it can grow on

Mueller–Hinton agar Mueller–Hinton agar is a microbiological growth medium that is commonly used for antibiotic susceptibility testing, specifically disk diffusion tests. It is also used to isolate and maintain ''Neisseria'' and ''Moraxella'' species. It typi ...

and

trypticase soy agar Trypticase soy agar or tryptone soya agar (TSA) and Trypticase soy broth or tryptone soya broth (TSB) with agar are growth media for the culturing of bacteria. They are general-purpose, nonselective media providing enough nutrients to allow f ...

Disease

''Neisseria cinerea'' is classified as a nonpathogenic bacterium, but has been isolated from numerous infections including acute meningitis. Many studies indicate that ''N. cinerea'' colonizes the oropharynx and sometimes the genital tract. A few infections which could possibly be caused by ''N. cinerea'' have been reported. However, in each case, the organism was misidentified as ''N. flavescens'', ''

'', or '' M. catarrhalis''.

References

External links