NEISSERIA
Pavithra G. Palan.
INTRODUCTION:

Gram negative aerobic cocci arranged in pairs.

Nonsporulating & nonmotile.

Oxidase positive.
CLASSIFICATION: Based on pathogenicity
1. Pathogenica) Neisseria meningitidis( Meningococcus )
b) Neisseria gonorrhoeae( Gonococcus)
2. Commensalsa) Neisseria flava
b) Neisseria subflava
c) Neisseria flavisans
Neisseria meningitidis
MORPHOLOGY:
 Gram negative cocci
arranged in pairs, with the
adjacent sides flattened.
 Each coccus is about
0.6-0.8 μm in diameter.
 They may be intra or
extracellular.
 They are nonmotile,
nonsporing & most of the
strains are capsulated.
Extracelluar
Intracellular
Pus cell
CULTURE & CULTURAL CHARACTERISTICS:

Meningococci are fastidious organisms do not grow on
ordinary culture media.

They are strict aerobes, no growth occur anaerobically.

The optimum temperature for growth is 35-36°C &
optimum pH is 7.4-7.6.

Growth is facilitated by 5-10% CO2.
Media used:
a) Non selective media: Blood agar,
Chocolate agar,
Muller-Hinton agar.
b) Selective media: Modified Thayer Martin medium,
New-York City medium.
Colony morphology: On chocolate agar the
colonies are small, round, convex, translucent, bluish
grey, smooth with entire edges.
BIOCHEMICAL REACTIONS:
1. Catalase test- Positive
2. Oxidase test- Positive
2. Glucose & maltose is fermented, but not sucrose,
producing acid but no gas.
PATHOGENICITY:
Source of infection:
1.
Asymptomatic nasopharyngeal carriers
2.
Patients
Mode of infection: Inhalation of respiratory
droplets
Antigenic structure & Virulence factors:
1. Capsule:
- Carbohydrate in nature.
- Based on their capsular antigens, meningococci are
classified into 13 serogroups, of which Groups A, B
& C are the most important.
- It is antiphagocytic.
2. Endotoxin (LPS): It damages vascular endothelium.
Antigenic structure & virulence factors of
Meningococcus
Mechanism of pathogenesis:
Entry of meningococci into nasopharynx by inhalation
Adherence to nasophayngeal mucosa
Colonization of nasopharynx
It reaches meninges through blood( bacteremia) or through
the olfactory nerve or through cribriform plate to the
subarachnoid space
On reaching the CNS, suppurative lesions of the meninges
will be set up
DISEASES:
(Meningococcemia)
1. Meningitis:

Meningococci causes purulent meningitis.

Clinical symptoms- Fever, head ache, stiff neck &
blurred vision.

Some cases develop chronic or recurrent
meningitis.
2. Meningococcal septicemia:

Presence of meningococci & its toxin in blood.

Clinical symptoms- Acute fever, chills, malaise,
prostration & typical petechial skin rash occurs early
in the disease.

Metastatic involvement of joints, ears, eyes, lungs &
adrenals may occur.
Petechial skin rashes
Purpura

A few develop fulminant meningococcemia
(Waterhouse-Friderichsen syndrome) characterized
by shock, disseminated intravascular coagulation &
multisystem failure.

Rarely chronic meningococcemia may be seen.
LABORATORY DIAGNOSIS:
Specimens to be collected:

CSF,

Blood,

Material from petechial skin lesion,

Nasopharyngeal swab.
Methods of examinations
1. Examination of CSF:
A) Macroscopic examination: The CSF will be turbid.
B) Biochemical examination:
Glucose level - decreased
Protein level
- increased
Lactic acid level - increased
C) Cytological examination: Shows polymorphs.
D) Bacteriological examination: The CSF is divided
into 3 portions.
a) One portion of CSF: is centrifuged.
i) From deposit: Gram stained smears are prepared.
Gram negative diplococci
will be seen mainly inside
polymorphs but often
extracellularly also.
ii) From supernatant: antigen may be demonstrated by
Latex agglutination
Counter immunoelectrophoresis.
b) Second portion of CSF: used for culture.
Media used:
Colony morphology:
Gram’s smear:
Reveals Gram negative cocci in pairs.
Biochemical reactions:
Slide agglutination: The isolated meningococcus is grouped by
using antisera.
c) Third portion of CSF: is incubated overnight as it
is or after adding equal volume of glucose broth &
subculture in chocolate agar or blood agar.
2. Blood culture: in meningococcemia & in early
cases of meningitis, Blood culture is positive.
3. Nasopharyngeal swab: useful for detection of
carriers. The swab should be held in a transport
medium (Stuart’s) till it is plated.
4. Material from petechial lesion: used for microscopy
& culture.
5. Autopsy specimens: used for microscopy & culture.
6. Serology: Antibodies to capsular polysaccharide
may be demonstrated by haemagglutination test.
TREATMENT:
 Penicillin G is the drug of choice.
 Chloramphenicol is used for penicillin allergic
persons.
 Ceftriaxone or Ceftazidime may be used for the
initiation of treatment before the etiology of
meningitis is known.
 After the initial course of treatment, eradicative
therapy is to be given with Rifampicin or
Ciprofloxacin to free the nasopharynx from the
cocci & to prevent carrier state.
EPIDEMIOLOGY:

Humans are the only reservoir of the
meningococcus.

The asymptomatic nasopharyngeal carriers serve to
infect their contacts.

Meningitis is more common in children below the
age of 5.
PREVENTION:
1.
Chemoprophylaxis: Rifampicin or Ciprofloxacin
is recommended.
2.
Immunoprophylaxis: Monovalent & polyvalent
vaccines containing the capsular polysaccharides
groups A, C, W-135 & Y are available.
Thank you