Sexually Transmitted Diseases  >  Gonorrhea  >  Laboratory Information  >  Related Species  >  Neisseria elongata

Neisseria elongata

Introduction

N. elongata is unusual among Neisseria species in being a rod-shaped organism in contrast to other Neisseria spp. which are diplococci. Also in contrast to most Neisseria spp., N. elongata is catalase-negative and superoxol-negative.

Images of colony morphology and results of biochemical tests have been included to aid the audience in recognizing and differentiating among Neisseria and related species.

Characteristics of N. elongata

Table 1. Characteristics of N. elongata

Characteristic	Illustration
Gram stain Cell Morphology	Gram-negative rod
Colony Morphology
Pigmentation	Image unavailable
Oxidase Test
Acid Production	No detectable acid from carbohydrates
Enzyme Substrate Test	Hydroxyprolylaminopeptidase-positive
Nitrate Reduction Test	Nitrate -ve
Polysaccharide from Sucrose	Polysaccharide -ve
Production of Deoxyribonuclease (DNase)	DNase -ve
Superoxol Test Reaction with 30% hydrogen peroxide	Superoxol-negative
Catalase Test Reaction with 3% hydrogen peroxide	Catalase-negative
Colistin Resistance	Colistin-susceptible

---

Species which may be misidentified as N. flavescens in acid detection tests

Table 2. Supplemental tests which permit differentiation among gram-negative diplococci that produce no detectable acid from carbohydrates.

reaction

Species that produce no detectable acid	Gram Stain	Enzyme Substrate	DNase	Superoxol	Polysaccharide from sucrose	Nitrate reduction	Colistin susceptibility
N. elongata	GNR	Hydroxy- prolylamino- peptidase +ve	-	-	-	-	S
N. flavescens	GND	Hydroxy- prolylamino- peptidase +ve	-	Weak (2+)	+	-	S
N. cinerea	GND	Hydroxy- prolylamino- peptidase +ve	-	Weak (2+) reaction	-	-	(R)
(Glucose-negative N. gonorrhoeae)	GND	Hydroxy- prolylamino- peptidase +ve	-	Strong (4+) reaction	-	-	R
M. catarrhalis	GND	No reaction	+	Strong (1+ to 4+) reaction	-	+	(R)

Abbreviations: GND, Gram-negative diplococcus; GNR, Gram-negative rod; +, most strains positive; -, most strains negative; R, strains grow well on selective medium for N. gonorrhoeae and/or show no inhibition around a colistin disk (10 micrograms); (R), most strains susceptible, some strains resistant.

---

Although enzyme substrate tests are intended to be used only for the identification of Neisseria spp. isolated on selective media for N. gonorrhoeae, these tests do provide additional information that may aid in accurately identifying an isolate. However, N. elongata produces hydroxyaminopeptidase in enzyme substrate test and may be misidentified as N. gonorrhoeae if additional tests are not performed.

Table 3. Supplemental tests which permit differentiation among Neisseria and related species that produce prolyl aminopeptidase in enzyme substrate tests.

Species that Produce PAP	Cellular Elongation*	Acid from					Nitrate Reduction	Polysaccharide from Sucrose	Superoxol	Colistin Resistance
		G	M	S	F	L
N. elongata	Rod filaments	-	-	-	-	-	-	-	-	S
N. flavescens	Diplococci	-	-	-	-	-	-	+	Weak (2+) positive	S
N. cinerea	Diplococci	-	-	-	-	-	-	-	Weak (2+) positive	(R)
N. gonorrhoeae "N. kochii"*	Diplococci	+	-	-	-	-	-	-	Strong (4+) positive	R
K. denitrificans	Rod filaments	+	-	-	-	-	+	-	-	R
N. subflava biovar subflava	Diplococci	+	+	-	-	-	-	-	Weak (2+) positive	S
N. subflava biovar flava	Diplococci	+	+	-	+	-	-	-	Weak (2+) positive	S
N. subflava biovar perflava	Diplococci	+	+	+	+	-	-	+	Weak (2+) positive	(R)
N. sicca	Diplococci	+	+	+	+	-	-	+	Weak (2+) positive	S
N. mucosa	Diplococci	+	+	+	+	-	+	+	Weak (2+) positive	S

Abbreviations: +, most strains positive; -, most strains negative; (-), strains may give weak positive reactions; R, strains grow well on selective medium for N. gonorrhoeae and/or show no inhibition around a colistin disk (10 micrograms); (R), most strains susceptible, some strains known to be resistant; S, all strains believed to be susceptible, no strains known to be resistant.

---

References

Bovre K. 1984. Family VIII. Neisseriaceae Prevot, p. 288-309. In N. R. Krieg (ed.). Manual of Systematic Bacteriology, vol. 1. The Williams & Wilkins co., Baltimore.

Knapp, J. S. 1988. Historical perspectives and identification of Neisseria and related species. Clin. Microbiol. Rev. 1:415-431.

Knapp JS, Rice RJ. Neisseria and Branhamella. In. Murray PR, Baron EJ, Pfaller MA, Tenover FC, Yolken RH. (ed.). Manual of Clinical Microbiology. 6th ed. American Society for Microbiology, Washington D. C, 1995.

Vedros NA. 1984. Genus I. Neisseria Trevisan 1885, 105AL, p. 290-296. In N. R. Krieg (ed.). Bergey's Manual of Systematic Bacteriology, vol. 1. The Williams & Wilkins Co., Baltimore.