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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

CharacteristicIllustration
Gram stain
Cell Morphology
 
Gram-negative rod
Colony Morphologycolonies
PigmentationImage unavailable
Oxidase Testoxidase
Acid Productionacid
No detectable acid from carbohydrates
Enzyme Substrate TestHydroxyprolylaminopeptidase-positive
Nitrate Reduction TestNitrate -ve
Polysaccharide from SucrosePolysaccharide
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 Resistancecolistin
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 StainEnzyme
Substrate

 
DNaseSuperoxolPolysaccharide
from sucrose
Nitrate
reduction
Colistin
susceptibility

N. elongata
GNRHydroxy-
prolylamino-
peptidase +ve
----S

N. flavescens
GNDHydroxy-
prolylamino-
peptidase +ve
-Weak (2+)
 
+-S

N. cinerea
GNDHydroxy-
prolylamino-
peptidase +ve
-Weak
(2+)
reaction
--(R)
(Glucose-negative
N. gonorrhoeae)
GNDHydroxy-
prolylamino-
peptidase +ve
-Strong (4+)
reaction
--R

M. catarrhalis
GNDNo
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 fromNitrate
reduction
Polysaccharide
from sucrose
SuperoxolColistin
Resistance
GMSFL
N. elongataRod filaments--------S
N. flavescensDiplococci------+Weak (2+)
positive
S
N. cinereaDiplococci-------Weak (2+)
positive
(R)
N. gonorrhoeae
"N. kochii"*
Diplococci+------Strong (4+)
positive
R
K. denitrificansRod 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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