Neisseria meningitidis and Neisseria gonorrhoeae, are obligate human pathogens that cause distinctly different disease syndromes. They are both Gram negative diplococci, non-sporing, oxidase positive and difficult to differentiate on morphological and cultural characteristics.
However, they can be differentiated on the following grounds:
|2.||Causative agent of||Sexually transmitted disease- Gonorrhoea||Causes a range of diseases embraced by the term invasive meningococcal disease. Most commonly cerebrospinal meningitis.|
|3.||Cell Morphology||Kidney shaped with apposing ends concave.||Semicircular diplococcus with flat apposing ends.|
|4.||Capsule||Absent||Capsule is present which is anti-phagocytic and an important virulence factor.|
|5.||Pili||N. gonorrhoeae most often moves using one retracting pilus.||N. meningitidis most often move using four pili.|
|6.||Plasmids||Usually possess plasmids, coding for drug resistant genes.||Rarely have plasmids|
|7.||Form||Predominantly exist in
|Exist in both intra· and
|8.||Movement||Movement of N. gonorrhoeae occurs at lower speed.||Movement of N. meningitidis occurs faster with a larger number of retracting pili.|
|9.||Growth on Blood Agar||N. gonorrhoeae grow less well on blood agar than N. meningitidis.||N. meningitidis grow well on blood agar than N. gonorrhoeae|
|10.||Culture medium||Contain antimicrobials that inhibit the growth of organisms other than N. gonorrhoeae; typically vancomycin (inhibits Gram-positive bacteria), colistin (inhibits gram-negative bacteria including the commensal Neisseria spp.), trimethoprim (inhibits swarming of Proteus spp.) and nystatin or amphotericin B (antifungal agents).||Blood agar, trypticase soy agar, supplemented chocolate agar, and Mueller-Hinton agar.|
|11.||Growth Rate||Slower than Meningococcus.||Slow|
|12.||Fastidious||Most fastidious among Neisseria spp.||Comparatively less fastidious.|
|13.||Colony morphology||N. gonorrhoeae form smooth, round, moist, uniform grey/ brown colonies with a greenish colour underneath on primary isolation medium.
Mostly, has a irregular margin.
|N. meningitides would form smooth, round, moist, uniform
large grey/brown colonies with a glistening surface and entire edges.
|14.||Sugar Fermentation||Produce acid from glucose only||Produce acid from glucose and maltose.|
|16.||Nitrite Reduction||N. gonorrhoeae doesn’t reduce nitrites.||N. meningitidis can reduce nitrites in low concentrations.|
|20.||Antigen Heterogeneity||More than meningococci.||Comparatively less.|
|21.||Grouping||Strains characterized by auxotyping which recognizes reqiurements for specific nutrients.||Serogroup is determined by its lipopolysaccharide capsular antigen.|
|22.||Normal Flora||Not considered as normal flora.||Many normal individuals may harbor Neisseria meningitidis in the upper respiratory tract|
|23.||Pathogen||It is always a pathogen.||It may or may not be pathogenic.|
|24.||Portal of Entry||Genital||Respiratory|
|25.||Site of Infection||Primarily causing infection of the anogenital tract.||Colonizes the upper respiratory tract as a commensal and occasionally invades to
cause systemic disease.
|26.||Virulence Factors||Pili, IgA proteases and production of lipopolysaccharide endotoxin.||LPS capsule, IgA protease and iron utilizationfrom transferrin.|
|27.||Related Conditions||N. gonorrhoeae can also cause conjunctivitis, pharyngitis, proctitis or urethritis, prostatitis, and orchitis.||Cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis.|
|28.||Specimens||Transport swab of endocervix, urethra, rectum, pharynx, conjunctiva, blood, joint fluid, aspirates from skin lesions.||Cerebrospinal fluid (CSF) and blood, swab skin lesions and nasopharynx.|
|29.||Presence in inflammatory exudates (pus)||In larger proportions||In less numbers|
|30.||Prevalence and Mortality||N.gonorrhoeae infections have a high prevalence and low mortality.||N. meningitidis infections have a low prevalence and high mortality.|
|31.||Superbug||Considered as “superbug”||Not considered as “superbug”|
|32.||Vaccines||No||Serogroup A, B, C, Y and W-135 meningococcal infections can be prevented by vaccines.|
- Greenwood, D., Slack, R. C. B., Peutherer, J. F., & Duguid, J. P. (1992). Medical microbiology: A guide to microbial infections : pathogenesis, immunity, laboratory diagnosis, and control. Edinburgh: Churchill Livingstone.
- Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
- Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.