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Gram Negative Cocci

Gram Negative Cocci. F4. Clinical Microbiology. ( MLCM- 201) Prof. Dr. Ebtisam.F. El Ghazzawi. Medical Research Institute (MRI) Alexandria University. Intended Learning Outcomes.

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Gram Negative Cocci

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  1. Gram Negative Cocci F4

  2. Clinical Microbiology (MLCM- 201) Prof. Dr. Ebtisam.F. El Ghazzawi. Medical Research Institute (MRI) Alexandria University

  3. 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.

  4. Neisseriae • The Neisseriae are gram-negative cocci resemble paired kidney beans and are oxidase positive. Neisseria gonorrhoeae Gram stain

  5. 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.

  6. 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.

  7. 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).

  8. I. Neisseriameningitidis 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.

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

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

  11. Diagnostic Laboratory Tests 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. Smears: Gram-stained smears of the sediment of centrifuged spinal fluid often show typical neisseriae within polymorphnuclear leukocytes or extracellularly.

  12. 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. Serology: Antibodies to meningococcal poly-saccharides can be measured by latex agglutination or hemagglutination tests. Fermentation test: N. meningitidis ferment both glucose and maltose.

  13. II. Neisseriagonorrheae 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

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

  19. 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. Fermentation test: N. gonorrhea ferment glucose only.

  20. Assignment Gram Negative cocci Neisseria.

  21. Questions Complete the following : • The Neisseriae are ………cocci resemble paired …………. and are…………positive. • Neisseria contains two important human pathogens:Neisseria………..and Neisseria…………..

  22. Meningococci have 3 virulence factors: • ……………. • …………….. • …………….. ……………constitute one of the most important virulence factors in gonorrheae.

  23. Recommended Textbooks Manual of Clinical Microbiology, Vols. 1 and 2: Eighth Edition Patrick R. Murray

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