2. General Characters of the Genus
1. Gram-negative diplococci

3. 2. Aerobic
3. Oxidase positive (the key test of the genus)

4. The genus includes:
 Many commensals
 Two important human pathogens:
1. Neisseria gonorrhoeae (gonococci)
2. Neisseria meningitidis ( meningococci)

5. . Morphology
. Culture characters:
- Enriched media: Chocolate agar
- Selective media: Modified Thayer Martin
(Chocolate agar + antibiotics)
. 5-10% CO2

6. Virulence Factors:
•
•
•
•
Pili
Outer membrane proteins
LOS
IgA protease

7. Diseases caused by N. gonorrehoeae
1. Gonorrhoeae : sexually transmitted disease (STD)
Men: acute urethritis
Women: cervicitis
prostate, bladder & epididymis
endometritis & salpingitis(PID)
2. Neonatal conjunctivitis
3. Vulvo-vaginitis
4. Oral infection

8. Gonorrhoeae
Urethral discharge
Cervical Discharge

9. Neonatal Conjunctivitis

10. Laboratory Diagnosis of Gonococcal
Infections

11. A. Specimen:
Urethral /Cervical Discharge / pharyngeal swabs

12. B. Gram-stained smear
In men: Intracellular Gram-negative diplococci (diagnostic)
In women: Less sensitive

13. C. Cultivation:

14. D. Identification:
 Identification at the genus level
Gram –ve diplococci
Oxidase +ve

15.  Identification at the species level
• Glucose utilization
Glucose
• Nucleic acid probe
Maltose

16. N. meningitidis
• Morphology: same + capsule
• Culture characters:
1. It grows on chocolate & MTM
2. It can also grow on blood agar
• Biochemical reactions:
. Oxidase positive.
. Utilization of glucose and
maltose (acid only)
Glucose Maltose

17. Virulence factors:
1. Polysaccharide Capsule is the most important at
least 13 serogroups , the most common A, B, C, Y,
and W135.
All highly immunogenic EXCEPT B.
2. LOS
3. Pili
4. IgA protease.

18. Diseases caused by N. meningitidis
N. meningitidis in the nasopharynx in 5- 30%
1. Meningitis
2. Meningococcemia
Skin rash

19. Laboratory diagnosis of
Meningococcal Meningitis
Medical emergency

20. 1. Specimen:
• CSF
• Blood
• Nasopharyngeal swab

21. 2. Direct Detection:
A. Gram-stained smear

22. B. Direct Meningococcal Antigen Detection
in CSF by:
 Latex Agglutination
 Report: within one hour to direct the antimicrobial
therapy.
 Definitive diagnosis by culture is essential to apply
the infection control measures

23. 3. Cultivation:
(CSF/
Nasopharyngeal
swab)

24. Blood culture technique
(1)
(2)
(3)

25. 4. Identification:
 Identification to the genus level

26.  Identification to the species level
• Sugar utilization
Glucose Maltose
• Antigen detection:
by latex agglutination or
immunofluorescence
• Nucleic acid probe

27. Meningococcal Vaccine
• Capsular polysaccharide vaccine (A,C,W135,Y)
• Protein conjugate vaccine:
Capsular polysaccharide vaccine + protein
for young children
• Given to groups at risk

28. Chemoprophylaxis
• Close contacts
• Doctors
2 days oral Rifampin
Or
One injection Ceftriaxone

30. 1. All of the following are characters of the
genus Neisseria EXCEPT:
a. Gram negative cocci
b. Arranged in pairs
c. Aerobic
d. Oxidase negative
e. Sugar fermentation identifies the species

31. 2. All of the following are true about
N. gonorrhea EXCEPT:
a. Can live intracellular
b. Oxidase positive
c. Produces acid only from glucose
d. Can grow on nutrient agar
e. Causes sexually transmitted diseases

32. 3. The following selective medium is
used to isolate N. gonorrhea:
a. Chocolate agar
b. Blood agar
c. MacConkey’s medium
d. Mannitol salt agar
e. Modified Thayer-Martin medium

33. 4. Culture of pathogenic Neisseria should
be incubated :
a. In humid atmosphere at 22 °C
b. In 5-10 % CO2
c. Anaerobically
d. Microaerophilically
e. 2-4 weeks

34. 5. N. meningitidis may be detected in all
of the following specimens EXCEPT:
a. CSF
b. Blood
c. Stools
d. Nasopharyngeal swab

35. Thank you