Neisseria cinerea was first characterized by W. von Lingelsheim in 1906 and originally named Micrococcus cinereus. Since first being described, N. cinerea has gone through many name changes in trying to correctly classify this Neisseria species. After extensive biochemical research, N. cinerea has been characterized as a non-pathogenic, gram-negative diplococcus found in the nasopharynx. Recently, contrary to the non-pathogenic classification, N. cinerea has been reported to be the causative agent in nosocomial pneumonia, endocarditis, proctitis and pediatric ocular infections. N. cinerea is non-sporeforming, non-motile, requires a moist environment and optimum growth occurs at 37° C.
Specific classification and identification of Neisseria species can be determined from the acid produced from the utilization of carbohydrates (glucose, lactose, maltose and sucrose). However, N. cinerea over oxidizes these acids to form carbon dioxide. Yet, acid detection test will show a positive reaction for the production of acids from carbohydrates - this results from the weak carboxylic acid produced as carbon dioxide is formed. Many tests are used to distinguish between species of Neisseria. One traditional test is the Cysteine Trypicase Agar (CTA) test made from a base medium supplemented with a 1% carbohydrate solution that is adjusted to pH 7.3. To detect the presence of acids, phenol red is also added to the medium. Another test, the QuadFERM+ test distinguishes Neisseria species from the carbohydrate utilized.
Other test to distinguish between Neisseria species are an enzyme substrate test (Hydroxyprolylaminopeptidase +ve), a nitrate reduction test, Colistin resistance or susceptibility and a superoxol test. N. cinerea produces a pink/red color in the enzyme test and shows resistance to Colistin. Colistin is an antibiotic effective against gram-negative bacteria.
Finding information on N. cinerea was difficult because most research on Neisseria species was on N. gonorrhoeae and N. mengitidis. There has been a push for more research on N. cinerea because of its similarity to N. gonorrhoeae. Many children who initially test positive for N. gonorrhoeae are subject to a sexual abuse investigation which may not be necessary.
References:
www.cdc.gov/ncidod/dastlr/gcdir/NeIdent/AcidDet.html
Boyce JM, Mitchell EB. Difficulties in Differentiating Neisseria cinerea from Neisseria gonorrhoeae. Journal of Clinical Microbiology, Nov 1985, p. 731 – 734.
Knapp JS, Totten PA, Mulks MH, Minshew BH. Characterization of Neisseria cinerea, a Nonpathogenic Species. Journal of Clinical Microbiology, Jan 1984, p. 63 – 67.
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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