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

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

, 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 ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular) or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria first isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. An obligate human pathog ...

''.

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 in ...

'' 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 first isolated by Albert Neisser in 1879. An obligate human pathogen, it primarily colonizes the ...

'' 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 or Madras eye, is inflammation of the conjunctiva, the thin, clear layer that covers the white surface of the eye and the inner eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness ...

, 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 thyrotoxic ...

Biochemical processes

''Neisseria cinerea'' can produce acid from

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

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

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

. 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 Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

, but it does reduce

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

Proline Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the p ...

arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) a ...

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 Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

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

immunoglobulin A Immunoglobulin A (IgA, 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 ty ...

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

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

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

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 type of growth medium used in microbiology to culture bacterial isolates and test their susceptibility to antibiotics. This medium was first developed in 1941 by John Howard Mueller and Jane Hinton, who were microbiologis ...

and

trypticase soy agar Trypticase soy agar or Tryptic soy agar (TSA) is a growth medium, growth media for the microbiological culture, culturing of moderately to non fastidious organism , fastidious bacteria. It is a general-purpose, non-selective media providing eno ...

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