Neisseria - Bacteriology - Lecture Slides, Slides of Bacteriology

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Neisseria

Key Words

• Neisseria
• Thayer Martin Medium
• Oxidase test
• N. gonorrhoeae
• Gonorrhea, Ophthalmia neonatorum, Septic arthritis
• N. meningitidis
• Meningitis, Cerebral spinal Fever, Waterhouse- Friedrichsen Syndrome

Neisseria

• Gram negative
• Diplococci (pairs of cocci)
• Oxidase positive
• Culture
  • Chocolate agar » heated blood (brown)
  • Thayer Martin.
    • selective
      • Incubation 35-36 C
      • 5-10% CO2 essential
      • Very delicate and autolytic

Modified Thayer-Martin Agar

• Colistin: Inhibits gram-negative flora ( N. gonorrhoeae and N. meningitidis resistant to colistin, most saprophyic species of Neisseria susceptible)
• Vancomycin: Inhibits gram-positive flora
• Nystatin: Inhibits yeast flora
• Trimethoprim: Inhibits swarming Proteus

Neisseria gonorrhoeae : Modes of Infection

• Neisseria gonorrhoeae spread by sexual

contact, including genital, anogenital, and

orogenital. Spread from infected mother to

neonate as ocular infection during birth.

Non-sexual transmission not documented.

• Found only in human
• Gonorrhea - Second most common venereal disease (after

c hlamydia trachomatis )

• N. gonorrhoeae of sexually-transmitted lower genital tract disease (acute urethritis in men, endocervicitis in women)
• N. gonorrhoeae untreated can progress to epididymitis, prostatitis, urethral stricture, salpingitis, tubo-ovarian abscess, and pelvic inflammatory disease

N. gonorrhoeae

the “Gonococcus"

Smear

• Polymorphonuclear cell
• Gram negative cocci
  • many in cells

• β lactamase-resistant cephalosporin
  • e.g. ceftriaxone
• Resistant strains
  • common
  • produce β lactamases
  • destroy penicillin

Antibiotic therapy

• Tissue injury
  • lipopolysaccharide
  • peptidoglycan

N. gonorrhoeae

• Resides in man only
• Usually sporadic cases
  • mostly young children
• Outbreaks
  • adults
  • crowded conditions

* e.g. army barracks, dorms

N. meningitidis

upper respiratory tract infection

• adhesion pili

bloodstream

brain

Neisseria meningitidis

• Second most common meningitis
  • pneumococcus, most common
• Fatal if untreated
• Responds well to antibiotic therapy
  • penicillin

Meningococcal meninigitis

Characteristics of N. meningtidis

• Neisseria meningitidis encapsulated (capsule the major virulence factor)
• Thirteen capsular polysaccharide serogroups
• Invasive infection caused by organisms with one of five capsular serogroups (A, B, C, Y, and W135) with 90% of meningococcal disease due to serogroups A, B, and C

• Capsule
  • inhibit phagocytosis
• Anti-capsular antibodies
  • stop infection
• Antigenic variation
  • sero-groups
• Vaccine
  • multiple sero-groups

Capsule