Neisseria flavescens
| Neisseria flavescens | |
|---|---|
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| A gram stain of Neisseria flavescens provided by CDC/Dr. W. A. Clark | |
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Betaproteobacteria |
| Order: | Neisseriales |
| Family: | Neisseriaceae |
| Genus: | Neisseria |
| Species: | N. flavescens |
| Binomial name | |
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Neisseria flavescens Branham 1930 |
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In 1928, Neisseria flavescens was first isolated from cerebrospinal fluid in the midst of an epidemic meningitis outbreak in Chicago. These gram-negative, aerobic bacteria reside in the mucosal membranes of the upper respiratory tract, functioning as commensals. However, this species can also play a pathogenic role in immunocompromised and diabetic individuals. In rare cases, it has been linked to meningitis, pneumonia, empyema, endocarditis, and septicemia.
These bacteria are gram-negative and diplococcus, rendering them virtually indistinguishable from the other Neisseria species. Yet, Neisseria flavescens remains distinct due to its signature pigmented colonies, yellow-gold in color. And it is through this yellow-gold color that this bacteria earned its name, with flavescens precisely translating as "becoming a golden yellow." This pigmentation also indicates N. flavescens' similarity to saccharolytic Neisseria species, which also exhibit pigmentation. In addition, these pigmented species differ from meningococcus, which lack pigmentation.
Similar to saccharolytic species, N. flavescens strains are capable of producing polysaccharides from sucrose and are colistin-susceptible. This bacteria is also catalase and oxidase positive. It is not capable of acid-production from glucose, maltose, fructose, sucrose, mannose, or lactose, in contrast to meningococcus, which are active-fermenters. Furthermore, fundamental differences between these two species are again shown, as serological testing reveals N. flavescens' lack of cross-agglutination. At the same time, biochemical testing distinguishes Neisseria flavescens from other gram-negative diplococci, with N. flavescens being DNase negative, weakly positive to Superoxol, and capable of prolyl aminopeptidase production in an enzyme-substrate test.
Though it shares many similarities with the saccharolytic species, Neisseria flavescens has a greater genetic relation to pathogenic Neisseria species, as molecular studies have shown. In addition, studies implicate that this species plays a role in penicillin-resistant strains of Neisseria meningitidis. The increasing selective pressure from penicillin treatment has led to N. meningitidis' uptake of an altered penicillin-binding protein gene, penA, from Neisseria flavescens via transformation. This modified penicillin-binding protein, also known as mecA, inhibits Neisseria meningitidis' transpeptidases from binding to the β-lactam portion of penicillin.
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