Gram Negative Cocci

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Gram Negative Cocci
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Clinical Microbiology

• (MLCM- 201)
• Prof. Dr. Ebtisam.F. El Ghazzawi.

Medical Research Institute (MRI) Alexandria
University
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Intended Learning Outcomes

• By the end of this lecture the student should be
  able to understand Gram negative cocci
  Neisseriae Types, pathogenesis ,Epidemiology
  and there Diagnostic Laboratory tests.

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Neisseriae

• The Neisseriae are gram-negative cocci resemble
  paired kidney beans and are oxidase positive.

Neisseria gonorrhoeae Gram stain
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• Neisseria contains two important human pathogens
  Neisseria gonorrhoeae (gonococci) and Neisseria
  meningitidis (miningococci).
• They are typically found associated with or
  inside polymorphonuclear cells. N. gonorrhoeae
  causes gonorrhea. It also causes neonatal
  conjunctivitis (ophthalmia neonatorum) and pelvic
  inflammatory disease.

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• N. meningitidis causes meningitis and
  meningococcemia. It is the leading cause of death
  from infection in children.
• N. meningitidis has a prominent polysaccharide
  capsule that enhances virulence by its
  antiphagocytic action.

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• N. gonorrhoeae has no polysaccharide capsule, it
  has three outer membrane proteins (proteins I, II
  and III) protein II plays a role in attachment of
  the organism to cells and varies antigenically as
  well.
• The endotoxin of N. meningitidis is a
  lipopolysaccharide (LPS) but the endotoxin of N.
  gonorrhoeae is a lipo oligosaccharide (LOS).

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I. Neisseria meningitidis
Pathogenesis and Epidemiology

• Humans are the only hosts for meningoccocci.
• The organisms are transmitted by airborne
  droplets, they colonise the membranes of the
  nasopharynx and become part of the transient
  flora of the upper respiratory tract.

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• From the nasopharynx, the organism can enter the
  bloodstream and spread to specific sites such as
  the meningis or joints, or be disseminated
  throughout the body.
• Meningococci have 3 virulence factors

1. A polysaccharide capsule that enables the
   organism to resist phagocytosis by
   polymorphonuclear leukocytes (PMNs).

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1. Endotoxin (LPS) which causes fever and shock.
2. An immunoglobulin A protease helps the bacteria
   attaches to the membrane of the upper respiratory
   tract.

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Diagnostic Laboratory Tests

1. Specimens Specimens of blood are taken for
   culture and specimens of spinal fluid are taken
   for smear, culture and chemical determinations.
   Nasopharyngeal swab cultures are suitable for
   carrier surveys.
2. Smears Gram-stained smears of the sediment of
   centrifuged spinal fluid often show typical
   neisseriae within polymorphnuclear leukocytes or
   extracellularly.

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1. Culture C.S.F. specimens are plated on chocolate
   agar and incubated at 37 C in an atmosphere of
   5 CO2. Presumptive colonies are identified by
   Gram-stain and oxidase test.
2. Serology Antibodies to meningococcal
   poly-saccharides can be measured by latex
   agglutination or hemagglutination tests.
3. Fermentation test N. meningitidis ferment both
   glucose and maltose.

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II. Neisseria gonorrheae
Pathogenesis and Epidemiology

• Gonococci like meningococci cause disease only in
  humans. The organism is usually transmitted
  sexually. Newborns can be infected during birth.
• Gonorrheae is usually symptomatic in men but
  often asymptomatic in women.

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• Genital tract infections are the most common
  source of the organism. Pili constitute one of
  the most important virulence factors, because
  they mediate attachment to mucosal cell surfaces
  and are antiphagocytic. The endotoxin of
  gonococci is weaker than that of meningococci.
  Gonococci have no capsules.

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• Gonococci cause both localized infections usually
  in the genital tract, and disseminated infections
  with seeding of various organs. Gonococci reach
  these organs via the bloodstream (gonococcal
  bacteremia). Gonorrhoeae in men is characterized
  by urethritis accompanied by dysuria and a
  purulent discharge.

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• In women infection is located primarily in the
  endocervix, causing a purulent vaginal discharge
  and intermenstrual bleeding (cervicitis). The
  most frequent complication in women is ascending
  infection of the uterine tubes (salpingitis)
  which can result in sterility.

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• Other infected sites include the anorectal area,
  throat and eyes. Anorectal infections occur in
  women and homosexual men. In the throat,
  pharyngitis occurs. In newborn infants, purulent
  conjunctivitis (ophthalmia neonatorum) is the
  result of gonococcal infection acquired from the
  mother during passage through the birth canal.

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Diagnostic Laboratory Tests

1. Specimens Pus and secretions are taken from the
   urethra, cervix, rectum, conjunctiva, or throat
   for culture and smear.
2. Smears Gram-stained smears of urethral or
   endocervical exudate reveal many diplococci
   within pus cells.

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1. Culture immediately after collection, pus or
   mucus is streaked on enriched selective medium
   (e.g. modified Thayer-Martin medium) and
   incubated in an atmosphere containing 5 CO2 at
   37 C.
2. Fermentation test N. gonorrhea ferment glucose
   only.

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Assignment

• Gram Negative cocci Neisseria.

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Questions

• Complete the following
• The Neisseriae are cocci resemble paired .
  and arepositive.
• Neisseria contains two important human
  pathogensNeisseria..and Neisseria..

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Meningococci have 3 virulence factors

• .
• ..
• ..
• constitute one of the most important
  virulence factors in gonorrheae.

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Recommended Textbooks

• Manual of Clinical Microbiology, Vols. 1 and 2
  Eighth Edition Patrick R. Murray

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