week 8

• Neisseria meningitis


  Gram negative, diplococci
• Virulence factors of Neisseria meningitis

  • Capsule and pili
  • IgA proteases (enzymes that break down antibody on mucus membrane)
  • Iron binding enzyme (can get to and use bodies iron)
  • Endotoxin producing strains (strain b and c are virulent, strain c is the one at UT recently)

  
• Mode of transmission for Neisseria meningitis

  Respiratory droplets
• Symptoms of Neisseria meningitis

  • Fever
  • Stiff neck
  • Headache
  • Rash (not alarming at first, but can rapidly progress to convulsions and coma)
• Rapid diagnosis for Neisseria meningitis

  Antibiotic can be given before CNS damage is too severe (penicillin and family antibiotics, rifampin given in prophylaxis)
• Vaccine for Neisseria meningitis is available but not that effective especially with children
• Meningitis can also be caused by viruses, such as Echovirus which tends to be mild
• Listeria monocytogenes


  Resistant organism to normal environmental properties, serious to fatal disease in elderly, very young, and immunocompromised (listeriosis from ingesting contaminated dairy products)

  
• Clostridium botulinum


  Gram positive, anaerobic spore forming bacillus, soil microbe
• Botulism

  Form of food poisoning, intoxication that produces the most potent of natural toxins
• Botulinum toxin


  • One of the most lethal substances known, blocks nerve functions and can lead to respiratory and muscular paralysis

  
• Types of botulism


  • Infant botulism (spores get into infant's intestines)
  • Wound botulism (spores get into a wound and make a toxin)
  • Foodborne toxin (eating contaminated food)

  
• Treatment for botulism


  Adults - antitoxin, Babies - supportive therapy and antibiotics

  
• Prevention of botulism


  Properly handling canned goods
• Clostridium tetani


  Gram positive, anaerobe, endospore forming soil organism
• Tetanus


  • Powerful exotoxin that is a neurotoxin, interferes with signals for muscular contraction and relaxation, causing muscle to stay contracted
• Tetanus treatment


  Treated with immunoglobulin (antitoxin), good vaccine - toxoid (DPT)
• Rabies is a fatal encephalitis caused by a rhabdovirus (RNA virus, bullet shaped and has an envelope)
• Rabies transmission


  Acquired by an animal bite or handling an infected animal (coyotes, skunks, raccoons, bats and other different strains)
• Rabies infection


  Virus has an affinity for nervous tissue, spreads from site of bite to nervous tissue, very slow progression toward the CNS
• Rationale for post exposure rabies treatment

  • Active and passive immunity
  • Injection of immunoglobulin at site of bite and then in the muscle
  • Injection of rabies vaccine to develop strong immunity before virus can travel to CNS
• Rabies vaccine


  Human diploid cell vaccine or chick embryo grown virus vaccine, 5 to 6 injections over 4 weeks (IM shot)
• Animal workers are now offered pre-exposure rabies vaccination (ID or IM)
• Polio or poliomyelitis


  Disabling and life-threatening disease caused by the poliovirus, virus spreads from person to person and can infect a person's spinal cord, causing paralysis
• Poliovirus


  Small non-enveloped virus (naked) called a picornavirus, acquired by contaminated food or water, fomites, and mechanical vectors
• Polio disease


  Usually limited to the throat, tonsils, and lymph nodes, but can affect the nerve tissue
• Polio treatment


  Supportive therapy
• Polio prevention


  • Salk vaccine (inactivated viral vaccine, trivalent)
  • Sabin vaccine (live attenuated virus), Salk for infants and Sabin for later
• WHO is still working on polio and measles to eradicate them
• Cryptococcus neoformans


  Causes meningitis, it is a yeast with a very large capsule
• Cryptococcus neoformans transmission


  Airborne from soil or bird droppings (pigeons)
• Cryptococcus neoformans meningitis


  Slow developing, travels from lungs to bloodstream to nervous system
• Cryptococcus neoformans diagnosis


  Presence of yeast and capsule in cerebrospinal fluid (CSF)
• Cryptococcus neoformans treatment


  Amphotericin B, infection is uncommon but very difficult to treat
• Now have a good antigen test used on CSF for Cryptococcus neoformans
• Arboviruses


  Viruses that are maintained in nature principally, or to an important extent, through biological transmission between susceptible vertebrate hosts by hematophagous (blood-sucking) arthropods
• Examples of arboviruses in the US

  • California encephalitis
  • Chikungunya
  • Dengue
  • Eastern equine encephalitis
  • Powassan
  • St. Louis encephalitis
  • West Nile
  • Yellow fever
  • Zika
• Arbovirus transmission


  Transmitted by mosquito bite, with horses and birds as the reservoir
• Arbovirus symptoms


  High fever, horrible headache, sometimes paralysis
• Arbovirus prevention


  Eliminate vector mosquito (spray and eliminate standing water)