NEISSERIA

The genus Neisseria contains two important
pathogens:
1. Neisseria meningitidis
2. Neisseria gonorrhoeae.

N. meningitidis causes meningitis and
meningococcemia.

N. gonorrhoeae causes gonorrhea,neonatal
conjunctivitis (ophthalmia neonatorum) and pelvic
inflammatory disease (PID).
 Properties:
Neisseriae are gram-negative diplococci ( Bean
shaped).
 Oxidase-positive; i.e., they possess the enzyme
cytochrome c and produce oxidase.
 They are cultured on "chocolate" agar
 N.meningitidis is maltose fermenter
 N. gonorrhoeae is maltose non fermenter
 N.meningititidis produces no beta lactamases.
 Some of N. gonorrhoeae produce beta lactamases.

Meningococcus has at least 13 serogroups on the
basis of capsular polysaccharides. Important ones
are A,B,C,Y and W-135.
 The endotoxin of N. meningitidis is a
lipopolysaccharide (LPS) but the endotoxin of N.
gonorrhoeae is a lipooligosaccharide (LOS).
 N.meningitidis is encapsulated while N.gonorrhoea
has no capsule


PILLI
NEISSERIA MENINGITIDIS:
 Pathogenesis:
 Humans are the only natural hosts


The organisms are transmitted by airborne
droplets

Colonize the nasopharynx and become transient
flora of the upper respiratory tract.

From the nasopharynx, the organism can enter the
bloodstream and spread to meninges or cause
meningococcemia.

N. meningitidis is the most common cause of
meningitis in persons between the ages of 2 and 18
years.

Outbreaks of meningitis are most common in
winter and early spring, and favored by close
contact between individuals.

It has three important virulence factors:
1. Polysaccharride capsule. It is antiphagocytic in
nature.
2. Endotoxin. It induces septic shock by causing
release of cytokines.
3. IgA protease. It cleaves the IgA antibodies present
in respiratory mucosa

Clinical Findings:
1. Meningitis
2. Meningococcemia
1.Meningitis. The symptoms are fever, headache, stiff
neck, and an increased level of Neutrophils in spinal
fluid.
2.Meningococcemia.

It occurs due to multiplication of bacteria in the
blood stream.

The severe form of it is life-threatening
Waterhouse-Friderichsen syndrome.

It is the septic shock induced by meningococcus

Also called Fulminant meningococcemia.

Feature include high fever, shock, widespread
purpura, disseminated intravascular coagulation,
thrombocytopenia, and adrenal insufficiency due to
bilateral adrenal hemorrhages.
 Laboratory
Diagnosis:
A. Specimens include.
1. Blood for culture and smears
2. Spinal fluid for smear, culture, chemical
analysis.
B. Blood smears on gram staining show gram
negative bean shaped diplococci.
C. Culture. The organism grows best on chocolate
agar incubated at 37°C in a 5% CO2 atmosphere.
Colonies are transparent or opaque.
D. Oxidase test. Positive
E. Manitol fermentation. The difference between N.
meningitidis and N. gonorrhoeae is made on the
basis of manitol fermentation. Meningococci
ferment maltose, whereas gonococci do not
F.
Latex agglutination test, which detects capsular
polysaccharide in the spinal fluid.
Prevention:
 Chemoprophylaxis and immunization both used for
prevention.
 Rifampin or ciprofloxacin used for prophylaxis in
people who had close contact with the patient
 There are two forms of the meningococcal vaccine,
each contains the capsular polysaccharide of groups
A, C,Y, and W-135 as antigens (Tetravalent vaccine)
1. Unconjugated
2. Conjugated

 Neisseria
gonorrhoeae: (Goonococcus).

Non motile.

Humans are only reservoir, not part of normal flora
Causes disease only in humans.
 Killed by drying that’s why transmitted sexually.


Pathogenecity:

The virulence factors are.
1.
Pili. Most important virulence factors.

Piliated gonococci are usually virulent, whereas non
piliated strains are avirulent.
2.
Two virulence factors in the cell wall
a. Lipooligosaccharride (LOS) (a modified form of
endotoxin). Endotoxin of gonococci is weaker than that
of meningococci.
b. Outer membrane proteins.(OMP).

3.
OMP cause attachment of bacteria to epithelial cells of the
urethra, rectum, cervix, pharynx, or conjunctiva, like pilli.
IgA protease.

The main host defenses against gonococci are antibodies
(IgA and IgG), complement, and neutrophils.

IgA protease degrades one of these antibodies.

Certain strains of gonococci cause disseminated infections.

These gonococci resist killing by bacteria due to protein
Porin A (OMP).

It inactivates the C3b component of complement.
PILLI

Clinical Findings:
 Transmitted sexually both in males and females.

Cause pyogenic infections.

Females are usually asymptomatic.

N. gonorrhea causes following infections.
1. Genitourinary tract infections ( Gonorrhea)
2. Disseminated infection via spread through blood
stream.
3. Rectal infections.
4. Pharyngitis
5. Ophthalmia neonatorum
1. Genitourinary tract infections :

Gonorrhea in men has features of urethritis
accompanied by dysuria and a purulent discharge.
Epididymitis can occur.

In women, infection is initially in the endocervix
(cervicitis), causing a purulent vaginal discharge and
intermenstrual bleeding.

The most frequent complication is ascending
infection to the uterine tubes (salpingitis) which
can lead to sterility or ectopic pregnancy
2. Disseminated gonococcal infection(DGI):

Commonly manifest as arthritis, synovitis, or skin
pustules.

Disseminated infection is the most common cause
of septic arthritis in sexually active adults.
3.Rectal infections:

Prevalent in male homosexuals, are characterized by
constipation, painful defecation, and purulent
discharge.
4.Pharyngitis is contracted by oral-genital contact. The
condition may mimic a mild viral or a streptococcal
sore throat.
5.Ophthalmia neonatorum is an infection of the
conjunctiva acquired by a newborn during passage
through the birth canal of an infected mother .
 If untreated, acute conjunctivitis may lead to
blindness.
 Lab
diagnosis:
1.In the male, the finding of numerous neutrophils
containing gram negative diplococci in a smear of
urethral exudate provides a diagnosis of gonococcal
infection.
2.In the female a positive culture is also needed.
3.Culture:
 N. gonorrhoeae grows best under aerobic
conditions, and most strains require CO2 also.

Gonococci are very sensitive to heating or drying.
Cultures must be plated rapidly.

N. gonorrhoeae grows rapidly producing small,
raised, grey or translucent colonies after overnight
incubation.
4. Oxidase test. Positive.
Prevention
 The prevention of gonorrhea involves the use of
safety measures and the immediate treatment of
symptomatic patients and their contacts.
