Gram (-) Cocci

• Gram Negative Cocci

  • Neisseria
  • Moraxella catarrhalis
  • Acinetobacter
• Neisseria


  Gram (-) aerobic cocci<|>Gonococci & Meningococci<|>Non-motile diplococci<|>Pyogenic cocci<|>Differentiated in the lab (not microscopic) by sugar-use patterns & site of primary infections

  
• Neisseria gonorrhea


  Causes gonorrhea<|>Gram (-) diplococcus<|>Transmitted during sexual contact or, more rarely, during passage of baby through an infected birth canal<|>Does not survive long outside human body (highly sensitive to dehydration)

  
• Neisseria gonorrhea structure


  • Unencapsulated (unlike meningococci)
  • Piliated (enhances attachment to host cell surface; antigenic)
  • Non-motile
  • Paired kidney beans

  
• Neisseria gonorrhea clinical significance


  Most often colonize the mucous membrane of the GUT or rectum with the production of pus, tissue invasion, chronic inflammation, and fibrosis<|>Females are generally asymptomatic and act as the reservoir for maintaining and transmitting gonococcal infections

  
• Neisseria gonorrhea genito-urinary tract infections

  1. More acute and easier to diagnose in males

  2. Yellow, purulent urethral discharge and painful urination

  3. In females, infection occurs in the endocervix and extends to the urethra and vagina

  4. Greenish-yellow cervical discharge is most common, often accompanied by intermenstrual bleeding

  5. May progress to the uterus, causing salpingitis (inflammation of fallopian tubes), pelvic inflammatory disease (PID), and fibrosis
• Neisseria gonorrhea rectal infections

  1. In men who have sex with men

  2. Constipation, painful defecation, and purulent discharge
• Neisseria gonorrhea pharyngitis


  Purulent pharyngeal exudate may mimic a mild viral or a streptococcal sore throat
• Ophthalmia neonatorum


  Conjunctival sac infection acquired by newborns during passage through infected birth canals<|>May lead to blindness

  
• Ophthalmia neonatorum treatment

  1. Systemic ceftriaxone IM or IV in a single dose

  2. Topical erythromycin ointment only for prophylaxis
• Neisseria gonorrhea lab identification


  Male: numerous neutrophils w/ G(-) diplococci in a smear of urethral exudate<|>Females: Positive culture<|>Thayer-Martin medium (chocolate agar w/ antibiotics that suppress growth of non-pathogenic Neisseria)
• Neisseria gonorrhea treatment and prevention

  More than 20% of current isolates are resistant to penicillin, tetracycline, cefoxitin, and/or spectinomycin<|>Ceftriaxone: single IM for uncomplicated infections of urethra, endocervix, & rectum<|>Spectinomycin<|>Doxycycline (w/ Chlamydia coverage)<|>Barrier method of contraception

  
• Neisseria meningitidis


  One of the most frequent causes of meningitis<|>Fulminant meningococcemia, with intravascular coagulation, circulatory collapse, and potentially fatal shock, but without meningitis<|>Extremely rapid onset and great intensity
• Neisseria meningitidis structure

  • Non-motile
  • Gram (-) diplococcus
  • Kidney bean shape, always appears in pairs
  • Piliated
  • Encapsulated when isolated from blood or spinal fluid

  
• Neisseria meningitidis epidemiology


  Transmission occurs through inhalation of respiratory droplets from a carrier or a patient in the early stages of the disease<|>Meningococcal disease in US is highest among infants <1 year
• Neisseria meningitidis clinical significance

  1. Initially colonizes the nasopharynx, resulting in a largely asymptomatic meningococcal pharyngitis

  2. Can cause disseminated disease by spreading through the blood, leading to meningitis and/or fulminating septicemia

  
• Neisseria meningitidis meningitis


  1. Joint symptoms and a petechial and/or purpuric rash

  2. Fever and malaise can evolve into severe headache, a rigid neck, vomiting, and sensitivity to bright lights

  3. Coma can occur within a few hours
• Neisseria meningitidis septicemia


  1. Very young children (Waterhouse-Friderichsen syndrome)

  2. Large, purple, blotchy skin hemorrhages, vomiting, diarrhea, circulatory collapse, adrenal necrosis, & death in 10-12 hrs
• Neisseria meningitidis lab identification


  Cultured on chocolate agar w/ increased CO2<|>Unlike gonococci, usually cultured from CSF or blood, which are normally sterile; therefore selective medium is not required<|>Thayer-Martin medium for samples obtained from skin lesion or nasopharyngeal swab, to eliminate contaminating organisms<|>Oxidase (+)<|>Utilizes both glucose & maltose (glucose only for N. gonorrhea)<|>CSF: increased pressure, elevated protein, decreased glucose & many neutrophils
• Neisseria meningitidis treatment and prevention

  1. Bacterial meningitis is a medical emergency

  2. Antibiotic treatment cannot await a definitive bacteriologic diagnosis

  3. Penicillin G or ampicillin (can pass the inflamed blood-brain barrier) in large intravenous doses

  4. When the etiology of the infection is unclear, cefotaxime or ceftriaxone is recommended

  5. Meningococcal vaccine (MCV4) for ages 11-55

  
• Moraxella catarrhalis


  Non-motile, Gram (-) paired coccobacilli<|>Aerobic, Oxidase- positive<|>Fastidious organisms that do not ferment carbohydrates<|>Can cause infections of the respiratory system, middle ear, eye, CNS, and joints
• Acinetobacter baumanii


  Non-motile coccobacilli<|>Frequently confused with Neisseria in gram-stained samples<|>Generally encapsulated<|>Oxidase (-)<|>Obligately aerobic<|>Do not ferment carbohydrates<|>Nosocomial (hospital-acquired) pathogen