Diseases of Nervous System & Eyes

- meningitis

- leprosy

2 ways bacteria infect cells of the nervous system

bacterial meningitis

can develop rapidly; associated with high fever, stiff neck, severe meningeal inflammation, and increased WBC's in CSF (milky appearance)

encephalitis

infection of the brain

cephalosporins (cefotaxime)

IV antibiotic used to treat bacterial meningitis

- Neisseria meningitidis

- Streptococcus pneumoniae

- Haemophilus influenzae

- Listeria monocytogenes

- Streptococcus agalactiae

5 species that cause 90% of bacterial meningitis

Neisseria meningitidis

bacteria also known as meningococcus (causes meningococcal meningitis); 5-10% of population are carriers (bacteria is readily phagocytosed in the nose/throat)

- infants (6 months-2 years)

- army recruits

- college students

populations meningitis caused by Neisseria meningitidis is comon in

epithelial cells of nose/pharynx (using pili)

Where does Neisseria meningitidis bind?

- fimbriae

- capsule (antiphagocytotic)

- endotoxin

pathogenesis of Neisseria meningitidis

- gram negative diplococci

- fastidious (grows only on chocolate agar)

- capsule

identification of Neisseria meningitidis

penicillin G

used to treat Neisseria meningitidis (along with steroids)

Streptococcus pneumoniae

bacteria that causes pneumonia, bacteremia, and pneumococcal meningitis (leading cause of meningitis in adults)

- acute otitis media

- sinusitis

- conjunctivitis

more common (but less severe) diseases caused by Streptococcus pneumoniae

throat, upper respiratory tract (high resistance in young healthy people)

Where is Streptococcus pneumoniae part of the normal flora in 5-40% of the population?

- lowered immune system

- splenectomy

- alcohol/drug intoxication (depresses phagocytic activity)

- smoking (irritates airways)

predisposing factors for invasiveness of Streptococcus pneumoniae

respiratory droplets, autoinoculation

How does Streptococcus pneumoniae spread?

- capsule

- enzymes

- toxins

pathogenesis of Streptococcus pneumoniae

- gram positive cocci in chains

- capsule

- catalase negative

- hemolysis alpha

identification of Streptococcus pneumoniae

Hemophilus influenzae

bacteria that was the leading cause of meningitis in children before the Hib vaccine was introduced (part of normal flora in upper respiratory tract)

- upper respiratory tract infection

- meningitis

- bacteremia/sepsis

- pneumonia

- otitis media

- sinusitis

diseases associated with Hemophilus influenzae

- capsule (resists phagocytosis)

- gram negative coccobacillus (short rods)

- NO exotoxin

- fastidious (grows on chocolate agar)

identification of Hemophilus influenzae

Hib vaccine

vaccine that protects against Hemophilus influenzae

Listeria monocytogenes

cause of meningitis and sepsis that is a concern in the food industry (presents as febrile gastroenteritis)

stomach acid suppressors (omeprazole)

drug that increases Listeria infection risk

low pH, high salt (refrigerator)

conditions Listeria can survive and grow in

cold deli foods (ex: raw sprouts, unpasteurized milk, soft cheese, deli meat, hot dogs)

foods associated with common foodborne illness outbreaks (Listeria)

- flu-like symptoms

- diarrhea

- meningitis symptoms (mental disorientation)

symptoms of Listeria

listeriolysin

virulence factor produced by Listeria monocytogenes that lyses the phagosome (lyses the phagosome, allowing it to escape into the immune cell cytosol)

- intracellular

- gram positive rods

- beta hemolysis

- listeriolysin

identification of Listeria monocytogenes

ampicillin (cephalosporin does NOT work)

antibiotic used to treat Listeria and Streptococcus agalactiae

Streptococcus agalactiae

leading cause of sepsis and meningitis in newborn babies (also impacts elderly and immunocompromised adults)

Group B streptococcus (GBS)

group that Streptococcus agalactiae is in (important with prenatal testing)

lower GI & genital tracts

Where is Streptococcus agalactiae part of the normal flora?

- capsule

- hemolysin

pathogenesis of Streptococcus agalactiae

- gram positive chains

- capsule

- beta hemolytic

- catalase negative

identification of Streptococcus agalactiae

botulism

rare but serious illness caused by Clostridium botulinum toxin that attacks the body's nerves, causing difficulty breathing, muscle paralysis, and death

foodborne botulism

botulism transmitted in honey, canned food (beans), and vacuum packed fish

honey

most common cause of infant botulism

wound botulism

botulism caused by drugs (ex: black tar heroin), accidents, and surgery

- flaccid body (paralysis)

- muscle weakness

- weak cry

- trouble breathing

symptoms of infant botulism

- respiratory failure

- blurry vision

- slurred speech

- difficulty breathing

symptoms of botulism in adults

blocks release of Ach by motor neurons (muscles cannot contract)

How does the botulism toxin cause muscle paralysis?

botox

drug that contains the botulism toxin, which induces partial paralysis (cosmetically used to reduce wrinkles)

peripheral nerves

target cells of Clostridium botulinum

- gram positive rods

- endospores

- obligate anaerobe

identification of Clostridium botulinum

Clostridium tetani

bacteria that causes tetanus

- soil

- dust

- intestines of humans/animals

Where is Clostridium tetani found?

- lockjaw

- painful muscle contractions

- irregular heartbeat/BP

- fatal without treatment

symptoms of tetanus (Clostridium tetani)

neurotoxin

pathogenesis of Clostridium tetani

- gram positive rods

- endospores

- obligate anaerobe

identification of Clostridium tetani

more readily cross blood-brain barrier (smaller)

Why do viral diseases of the nervous system occur more frequently than bacterial and fungal infections?

Enterovirus

virus that causes 90% of viral meningitis (aseptic meningitis)

- fecal contamination of food, water, or hands

- respiratory droplets

How is viral meningitis spread (Enterovirus)?

Paramyxovirus

viruses that cause mumps (parotid gland swelling)

virus in saliva (respiratory droplets, coughing, sneezing)

How is Paramyxovirus (mumps) transmitted?

epithelial cells of nose and upper respiratory tract

Where do Paramyxoviruses (mumps) replicate?

- tender, painful swelling of parotid glands (parotitis)

- swelling in testicles (orchitis)

- aseptic meningitis

- miscarriage

symptoms of Paramyxovirus (mumps)

Lyssavirus

virus that causes Rabies

bite/scratch from infected animals (bats, skunks, raccoons, foxes, dogs)

How is Lyssavirus (Rabies) transmitted?

- replicates in muscle cells

- spreads to neurons and CNS (encephalitis)

- salivary glands

Where does Lyssavirus (Rabies) replicate and spread to?

corneal & organ transplants

only documented cases of human-to-human transmission of Lyssavirus (Rabies)

variable (usually 1-3 months)

incubation period of Lyssavirus (Rabies)

- headache

- vomiting

- photophobia

initial symptoms of Lyssavirus (Rabies)

- hydrophobia

- aerophobia

- hallucination

- tearing

- salivation

later symptoms of Lyssavirus (Rabies)

- seizures

- paralysis

- viral encephalitis

- coma/death

end stage symptoms of Lyssavirus (Rabies)

highest = face/head

lowest = legs

bite locations associated with highest and lowest mortality for Lyssavirus (Rabies)

- bullet/rod shaped (rhabdovirus)

- postmortem detection of Negri bodies

- rhabdomyolisis (damages muscle cells and kidneys)

identification of Lyssavirus (Rabies)

togavirus

arbovirus associated with equine encephalitis (EEV); most severe

flavivirus

arbovirus associated with West Nile encephalitis (most common in US)

chikungunya virus

arbovirus associated with outbreaks in Africa and Asia (high fever, rash, joint pain)

by mosquitoes from bird swamps

How are EEV (togavirus) and WNV (flavivirus) transmitted?

horses

"dead end" vector for EEV (togavirus)

- myeloid/lymphoid cells (immune cells)

- vascular endothelium

- rarely in CNS (encephalitis)

Where do arboviruses multiply?

- flu-like symptoms

- mental confusion

- tremors

- coma

- meningitis & encephalitis

symptoms of arboviruses

macrophages

Where do arboviruses replicate?

Coccoidiodes immitis

fungus that causes fungal meningitis

spherule glycoprotein (adhesin)

pathogenesis of Coccidiodes immitis

Toxoplasma gondii

protist that sexually reproduces in cats and form oocysts that are passed in feces (can be transmitted to humans); infect eyes/brain

sporozoites

released by Toxoplasma gondii oocysts in the human gut, which cross into the blood to infect macrophages & lymph nodes (travel to brain and eye to form chronic cysts)

congenital toxoplasmosis

infected children may suffer impaired vision and mental retardation due to infections of the brain/retina (reason pregnant women must avoid cat feces)

- fever

- malaise

- inflammation of lungs, liver, heart

symptoms of Toxoplasma gondii

amygdala

area of the brain that Toxoplasma gondii affects in rodents, causing them to lose fear

- schizophrenia

- bipolar

psychiatric disorders associated with Toxoplasma gondii infection in humans

cat and human intestinal epithelial cells

Where does Toxoplasma gondii replicate?

- obligate intracellular

- parasitic protist

identification of Toxoplasma gondii

Daraprim

anti-parasitic medication used for Toxoplasma gondii (folace inhibitor)

Spongiform encephalopathies (leaves brain with spongy holes)

diseases caused by prions (infectious proteins)

- spontaneously (mutated normal prions)

- inherited

- consuming meat from infected animals

How do prion diseases occur (Spongiform encephalopathies)?

- insomnia

- weight loss

- memory failure

- progressive worsening of muscle control

symptoms of prion disease (Spongiform encephalopathies)