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Gonorrhea Laboratory Information
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 colonies
Pigmentation Image unavailable
Oxidase Test oxidase
Acid Production acid
No detectable acid from carbohydrates
Enzyme Substrate Test Hydroxyprolylaminopeptidase-positive
Nitrate Reduction Test Nitrate -ve
Polysaccharide from Sucrose Polysaccharide
Polysaccharide -ve
Production of
Deoxyribonuclease (DNase)
DNase
DNase -ve
Superoxol Test
Reaction with 30% hydrogen peroxide
superoxol
Superoxol-negative
Catalase Test
Reaction with 3% hydrogen peroxide
catalase
Catalase-negative
Colistin Resistance colistin
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.

 

 
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