BMS150 Wk 6 lec 3

Bacterial Meningitis

• Inflammatory bacterial infection of the meninges, particularly the pia and arachnoid mater
• Causes meningial swelling, restricting CSF flow, and putting pressure on the organs, leading to nausea, pain, vomiting, and reduced brain function
• If the infection is in the spinal cord, muscles of the neck will become stiff, and motor control will be reduced
• If the infection is in the brain (encephalitis), sensory perceptions are decreased, behavioral changes occur, and coma or death may result

Testing for Bacterial Meningitis

• Cloudy CSF and positive meningitis test indicating bacterial infection
• Lumbar puncture (aka spinal tap) is used to collect CSF for testing

Many Bacteria Can Cause Bacterial Meningitis

• Opportunistic members of normal microbiota (e.g., Staphylococcus aureus, Streptococcus pyogenes, Klebsiella pneumoniae)
• Regular disease-causing bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Listeria monocytogenes)

Neisseria Meningitidis

• Causes meningococcal meningitis
• Virulence factors include fimbriae, polysaccharide capsules, lipooligosaccharide (with Lipid A/Endotoxin), and various factors to prevent digestion in phagocytes

Streptococcus Pneumoniae

• Leading cause of meningitis
• Virulence factors include capsule, secretory IgA protease, pneumolysin (inactivator of lysosomal enzymes)
• Primary virulence factor: phosphorylcholine (attachment to cells of lungs, meninges, blood vessels – and triggers endocytosis)

Listeria Monocytogenes

• Gram-positive coccobacillus found in soil, water, and many animals
• Obtained through contaminated food/drink
• Causes meningitis in immunocompromised individuals, but only mild flu in healthy adults
• Avoids immune system detection by dividing inside macrophages and epithelial cells

Pathogenesis of Bacterial Meningitis

• N. meningitidis, H. influenzae, S. pneumoniae – inhaled in respiratory droplets
• Listeria – through contaminated food/drink
• Bacteria usually spreads to meninges from infections of lungs, sinuses, or inner ear
• Head or neck trauma may expose meninges directly
• Bacteria ferment glucose in CSF for energy

Prevention

• Susceptible individuals should avoid undercooked veggies, unpasteurized milk, undercooked meat, and all soft cheese
• People living in dormitories should receive vaccinations

Hansen's Disease (Leprosy)

• Causative agent: Mycobacterium leprae
• Optimal growth – 30°C – so in the chilly parts of the body (peripheral nerve endings, earlobes, nose, tips of fingers and toes)
• Signs of disease may not be present for 10-30 years, but when the population becomes big enough, the immune system will aggressively attack them

Botulism

• Causative agent: Clostridium botulinum toxin (note: NOT an infection)
• 3 types of botulism: foodborne, infant, and wound
• Foodborne/Wound Botulism symptoms: paralysis of all voluntary muscles, blurred vision, nausea (death from respiratory paralysis)
• Infant botulism: not ingested, but C. botulinum can infect GI tract due to absence of microbiota

Tetanus

• Causative agent: Clostridium tetani
• Portal of entry: endospores enter through breaks in skin
• Signs/symptoms: tightening of jaw and neck muscles, difficulty swallowing, fever, spasms
• Treatment: aggressive treatment of wound, antibiotics
• Prevention: Vaccination

Tetanus Toxin (Tetanospasmin)

• Blocks release of inhibitory neurotransmitter, causing muscles to be fully contracted and unable to relax

West Nile Fever

• Absent from N. America until 1999
• New York isolate identical to Israeli goose
• Virus infects 100s of bird, 37 mosquito, 18 other vertebrate (including humans/horses) species

West Nile Virus Transmission Cycle

• Mosquito bite transmission

WNV - Pathogenesis

• Transmitted by mosquito bite
• Incubation period of 3-14 days
• 20-30% get flu-like illness called West Nile Fever
• 80% - NO symptoms
• 1/150 experience neuroinvasion

Epidemiology – US Cases

• Increased cases in the US since 1999

Epidemiology – Case Fatality Rate

• High case fatality rate

WNV Prevention

• Prevention measures to avoid mosquito bites

Poliomyelitis (Polio)

• Causative agent: Poliovirus
• Spread by fecal-oral transmission
• Peaks during warm months in temperate climates
• Complication: post-polio syndrome

Polio Epidemiology

• Decreased cases since the introduction of vaccination
• Americas/Europe: now "polio-free"

Emergence of Polio as an Epidemic in the 1900s

• Polio has only minor symptoms for infants and adults (seems like a mild cold)
• Early in the 1900s, white, wealthy children started getting paralytic polio
• Connection to modern plumbing, sewer systems, etc.

Learn about the inflammatory bacterial infection of the meninges, its causes, symptoms, and effects on the brain and spinal cord.