Gram-Negative Cocci

• Gram-negative cocci


  Neisseria gonorrhoeae
• Neisseria gonorrhoeae


  • Not part of normal human flora
  • Found on mucous membranes of genitalia, anorectal area, oropharynx, or conjunctiva at time of infection
  • Leading cause of sexually transmitted diseases
• Mode of transmission

  1. Person to person spread

  2. Infected mother to newborn during birth

  3. Asymptomatic carriers are a significant reservoir for increased disease transmission
• Virulence factors

  • Pili
  • Protein II
  • Outer membrane porin (PorB)
  • Capsule
  • Lipooligosaccharide (endotoxin)
  • Outer membrane proteins I-III
• Spectrum of disease and infections

  • Sexually transmitted diseases
  • Pelvic inflammatory disease (PID)
  • Localized infections
  • Disseminated infections
• Sexually transmitted diseases in males

  • Acute purulent urethritis
  • Prostatitis
  • Epididymitis
• Sexually transmitted diseases in females

  • Acute purulent urethritis
  • Acute cervicitis
  • Can lead to Pelvic Inflammatory Disease (PID)
• Pelvic inflammatory disease (PID)


  • Infection of the uterus (endometritis)
  • Fallopian tubes (salpingitis)
  • And/or ovaries (oophoritis)
• Complications of PID

  • Sterility
  • Ectopic pregnancy
  • Abscesses
  • Peritonitis
  • Peri-hepatitis (Fitz-Hugh-Curtis syndrome)
• Localized infections

  • Pharyngitis
  • Anorectal infections
  • Conjunctivitis (ophthalmia neonatorum of newborns)
• Disseminated infections

  • Bacteremia
  • Arthritis
  • Metastatic infection at other body sites
• Specimen collection and transport

  • Species are sensitive to drying and extremes of temperature, and material must be cultured promptly to enhance recovery
  • Pus and secretions are taken from the urethra, cervix, rectum, conjunctiva, throat, or synovial fluid for culture and smear
  • Blood culture is necessary in systemic illness
  • N. gonorrhea and meningitidis are sensitive to sodium polyanethol sulfonate (SPS), the preservative typically found in blood culture broths - SPS content should not exceed 0.025%
• Transport

  • If cotton swabs are used, transport medium should contain charcoal (Ames medium) to inhibit toxic fatty acids present in the fibers
  • Sample should then be placed in a container able to sustain an atmosphere of increased carbon dioxide
  • Specially packaged media contain a CO2-generating system are commercially available (JEMBEC plates)
• Gram stain

  Gram-negative diplococci inside polymorphonuclear leukocytes or neutrophils
• Culture media of choice

  • Chocolate agar
  • Thayer-Martin medium
  • Modified Thayer-Martin (MTM)
  • Martin Lewis (ML)
  • GC-LECT agar
  • New York City (NYC)
• Incubation conditions and duration

  • Incubated at 35° to 37°C for 72 hours in a CO2-enriched (3 to 7%), humid atmosphere
  • Achieved using a CANDLE JAR, CO2 generating pouch and CO2 incubator
  • Humidity can be provided by placing a pan with water in the bottom of a CO2 incubator or by placing a sterile gauze pad soaked with sterile water in the bottom of a candle jar
• Colonial appearance

  • Small, grayish white, convex, translucent, shiny colonies with either smooth or irregular margins
• Biochemical and physiologic characteristics

  • Facultative anaerobe
  • Oxidase positive
  • Ferments = glucose only
  • DNAse negative
• Treatment and antimicrobial susceptibility

  • Widespread resistance to penicillin, tetracycline and fluoroquinolones
  • Treatment: extended spectrum cephalosporins
  • Antimicrobial susceptibility testing (AST) should be performed if symptoms persist after treatment
• Prevention

  • Use of preexposure antibiotics to prevent gonococcal disease is discouraged because of the potential risks of sensitization and the emergence of resistant strains
  • Erythromycin ointment to the eyes of newborns to prevent gonococcal (and chlamydial) ophthalmia
• Neisseria meningitidis

  • Colonizes oropharyngeal and nasopharyngeal mucous membranes of humans
  • Humans commonly carry the organism without symptoms. So, humans are asymptomatic carriers
  • The leading cause of fatal bacterial meningitis
• Mode of transmission

  Person-to-person spread by contaminated respiratory droplets (like COVID), usually in settings of close contact
• Virulence factors

  • Pili
  • Capsule
  • Endotoxin (LPS)
  • Cellular proteins similar to N. gonorrhoeae
  • IgA protease
• The capsule is antiphagocytic and there are 9 serogroups (A, B, C, D, X, Y, Z, W135, and 29E)
• The endotoxin (LPS) causes blood vessel destruction (hemorrhage) and sepsis, seen on the skin as tiny, round, red dots of hemorrhage called petechiae
• Neisseria meningitidis

  Colonizes oropharyngeal and nasopharyngeal mucous membranes of humans
• Humans commonly carry the organism without symptoms, so they are asymptomatic carriers
• Neisseria meningitidis is the leading cause of fatal bacterial meningitis
• Mode of transmission

  Person-to-person spread by contaminated respiratory droplets, usually in settings of close contact
• Virulence factors of Neisseria meningitidis

  • Pili facilitate attachment to mucosal epithelial cells and invasion to the submucosa
  • Capsule is antiphagocytic and has 9 serogroups (A, B, C, D, X, Y, Z, W135, and 29E)
  • Endotoxin (LPS) causes blood vessel destruction (hemorrhage) and sepsis, seen on the skin as petechiae
  • Cellular proteins similar to N. gonorrhoeae include Opa, two porin proteins (PorA and PorB), and IgA protease which degrades membrane associated IgA, increasing the host's susceptibility to invasion
• Spectrum of disease and infections caused by Neisseria meningitidis

  • Meningococcemia
  • Fulminant meningococcemia (Waterhouse Friderichsen syndrome)
  • Meningitis
  • Less common infections (conjunctivitis, pneumonia, sinusitis)
• Meningococcemia


  Intravascular multiplication of N. meningitidis that can lead to meningitis and/or fulminant meningococcemia
• Fulminant meningococcemia (Waterhouse Friderichsen syndrome)


  • Involves septic shock, bilateral hemorrhage into the adrenal glands causing adrenal insufficiency, abrupt onset of hypotension and tachycardia, rapidly enlarging petechial skin lesions, can lead to DIC and coma, death can occur rapidly (6-8 hours)
• Meningitis


  • Usually striking infants < 1 year of age, with nonspecific findings like fever, vomiting, irritability, and/or lethargy. Neonates may have bulging open anterior fontanelle. Slightly older infants may have stiff neck and positive Kernig's and Brudzinski's signs.
• Specimens for laboratory diagnosis

  • Blood
  • CSF
  • Nasopharyngeal swab
  • Puncture material from petechiae
• Culture media

  5% sheep blood, chocolate agar, some strains use selective media similar to N. gonorrhoeae
• Gram stain

  • Gram-negative, cocci in pairs, kidney-bean shaped with adjacent sides flattened, similar to N. gonorrhoeae
• Colonial appearance on culture

  • Medium, smooth, round, moist, gray to white; encapsulated strains are mucoid; may be greenish cast in agar underneath colonies
• Gram-negative diplococci with flattened adjacent sides
• Biochemical and physiologic characteristics

  • Facultative anaerobe, oxidase positive, ferments glucose and maltose (unlike N. gonorrhoeae which only ferments glucose), DNAse negative