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NEISSERIA

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NEISSERIA * The genus Neisseria contains two important pathogens: 1. Neisseria meningitidis 2. Neisseria gonorrhoeae. N. meningitidis causes meningitis and ... – PowerPoint PPT presentation

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Title: NEISSERIA


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NEISSERIA
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  • 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).

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  • 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.

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  • 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

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PILLI
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  • 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.

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  • 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.

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  • 2. Endotoxin. It induces septic shock by causing
    release of cytokines.
  • 3. IgA protease. It cleaves the IgA antibodies
    present in respiratory mucosa

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  • 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.

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  • 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.

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  • 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 37C in a 5 CO2
    atmosphere. Colonies are transparent or opaque.

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  • 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

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  1. Latex agglutination test, which detects capsular
    polysaccharide in the spinal fluid.

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  • 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

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  • Neisseria gonorrhoeae (Goonococcus).
  • Non motile.
  • Humans are only reservoir, not part of normal
    flora
  • Causes disease only in humans.
  • Killed by drying thats why transmitted sexually.

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  • Pathogenecity
  • The virulence factors are.
  • Pili. Most important virulence factors.
  • Piliated gonococci are usually virulent, whereas
    non piliated strains are avirulent.
  • 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).

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  • 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.

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PILLI
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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • 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.

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  • Prevention
  • The prevention of gonorrhea involves the use of
    safety measures and the immediate treatment of
    symptomatic patients and their contacts.
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