Gram (-) Cocci

• Neisseria:

  • Gram (-) cocci
  • Aerobic cocci
  • Includes N. gonorrhea and N. meningitidis
  • Non-motile diplococci
  • Differentiated in the lab by sugar-use patterns & site of primary infections
• Neisseria gonorrhea:

  • Causes gonorrhea, a frequently reported infectious disease in the US
  • Transmitted during sexual contact or passage of baby through infected birth canal
  • Gram (-) diplococcus
  • Structure: unencapsulated, piliated, nonmotile, paired kidney beans
  • Clinical Significance:
  • Colonizes mucous membrane of the GUT or rectum, leading to pus production, tissue invasion, chronic inflammation, and fibrosis
  • Females are often asymptomatic carriers
  • Genito-urinary tract infections more acute and easier to diagnose in males
• • In females, infection extends from endocervix to urethra and vagina, with greenish-yellow discharge and intermenstrual bleeding
  • May progress to uterus, causing salpingitis, PID, and infertility
  • Also causes rectal infections, pharyngitis, and ophthalmia neonatorium
  • Lab Identification: G(-) diplococci in urethral exudate smear, positive culture on Thayer-Martin medium
  • Treatment & Prevention: Ceftriaxone, azithromycin, doxycycline, barrier contraception
• • Treatment & Prevention: Penicillin G, ampicillin, cefotaxime, ceftriaxone, meningococcal vaccine
• Neisseria meningitidis:

  • Causes meningitis and fulminant meningococcemia
  • Rapid onset and intense symptoms
  • Structure: nonmotile, gram (-) diplococcus, kidney bean shape, piliated, encapsulated in blood or spinal fluid
  • Epidemiology: Transmission through respiratory droplets, highest among infants <1 year
  • Clinical Significance: Initially colonizes nasopharynx, leading to meningitis and septicemia
  • Lab Identification: Cultured on chocolate agar, oxidase (+), utilizes glucose & maltose, CSF findings
• Moraxella catarrhalis:

  • Nonmotile paired coccobacilli
  • Aerobic, oxidase-positive
  • Causes respiratory, middle ear, eye, CNS, and joint infections
• Acinetobacter baumanii:

  • Nonmotile coccobacilli
  • Encapsulated, oxidase (-), obligately aerobic
  • Nosocomial pathogen, often confused with Neisseriae in gram-stained samples