Chapter 17 Infectious Disease of the Nervous System

central nervous system (CNS)

brain and spinal cord

peripheral nervous system (PNS)

extensive network of nerves connecting the CNS to the muscles and sensory structures

meningitis

inflammation (swelling) of the protective membranes covering the brain and spinal

affects CNS

initially affects GI tract, then infects nervous system

cause = neisseria

neisseria

bacteria that causes meningitis

gram-negative bean shaped diplococci

residents of mucous membranes of warm-blooded animals

2 human pathogens:

______ gonorrhoeae = causes gonorrhea

______ meningitidis = cause of meningococcal meningitis

neisseria meningitidis

aerobic or microaerophilic

produce catalase and oxidase

N. meningitidis virulence factors

capsule = protects bacteria from being engulfed/killed through phagocytosis

adhesive fimbriae (no flagella or spores)

endotoxin: polysaccharide capsule that protects against phagocytosis

N. meningitidis

prevalent cause of meningitis

human reservoir —> nasopharynx 

high risk in those living in close quarters, 6-months-3 years of age, children and young adults 10-20 years

N. meningitidis

disease that begins when bacteria enters bloodstream, cross the blood-brain barrier, permeate the meninges, and grow in the cerebrospinal fluid

VERY rapid onset —> cause hemorrhage and shock due to endotoxin (fatal) 

N. meningitidis diagnosis

gram stain CSF (spinal fluid), blood, or nasopharyngeal sample

culture

rapid tests for capsular polysaccharide

N. meningitidis treatment

treated with IV penicillin, cephalosporin

prophylactic treatment of family members, medical personnel, or children in close contact

vaccine available

Group B Streptoccocus agalactiae

resides in vagina, pharynx, and large intestine

can be transferred to infant during delivery and cause severe infection

most prevalent cause of neonatal pneumonia, sepsis, and meningitis

alpha-hemolytic streptococci: Streptococcus pneumoniae

causes 60-70% of all bacterial pneumonias

culture requires blood or chocolate agar

small cells arranged in pairs and short chains

Streptococcus pneumoniae

causes pneumonia and otitis

all pathogenic strains form large capsules (major virulence factors)

90 different capsular types have been identified

S. pneumoniae 

predisposing factors: 

age (young children, elderly) 

immune conpromised

season (winter) 

those with other lung diseases 

persons living in close quarters

S. pneumoniae diagnosis

capsular swelling reactions

a-hemolytic test (blood agar)

S. pneumoniae treatment

traditionally treated with penicillin

increased drug resistance (15% of isolates show resistance)

Hemophillus influenzae

invasive diseases that cause this:

pneumonia

blood stream infection

meningitis

epiglotittis

cellulitis

infectious arthritis

Listeria monocytogenes

gram positive, coccobacilli

common cause: eating frozen food contaminated with this bacteria

causes:

• generalized blood infection

• inflammation of the membranes and fluid surrounding the brain (meningitis) 

ampicillin

antibiotic used to treat listeria

usually works in early stage of infection

listeria prevention

pasteurization and thoroughly cooking food

Listeria

at risk populations of this bacteria:

immunocompromised patients, fetuses, and newborns

affects brain and meninges —> increases death rate once infected here

clostridium

species: 

botulism

colitis

tetanus

septic absorption 

gas gangrene

clostridial food poisoning

botulism

caused by a toxin that attacks the body’s nerves and causes difficulty breathing, muscle paralysis, and even death

toxin is made by Clostridium botulinum and sometimes Clostridium butyricum and Clostridium baratii bacteria

Clostridium botulinum

Clostridium butyricum

Clostridium baratii

toxins that cause botulism

botulinum toxin

lethal neurotoxin that causes a rare life-threatening neuroparalytic disease

botulinum toxin

prevents the release of acetylcholine (Ach) at the peripheral nerve endings, stops muscle contraction followed by paralysis

botulinum diagnosis

determine the presence of toxin in food, intestinal contents or feces

botulinum treatment

administer antitoxin

infectious botulinum is treated with penicillin

botulinum prevention

proper methods of preserving and handling canned foods

Clostridium tetani - tetanus

common resident of soil and GI tract of animals

causes tetanus (lockjaw) - neuromuscular disease

most common among geriatric patients, IV drug abusers, and infants in developing countries

tetanus

spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts

anaerobic environment is required for vegetative cells to grow and release toxin (tetanospasmin)

tetanospasmin

neurotoxin that causes paralysis by binding to motor nerve endings; blocks the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably —> spasms

death most often due to paralysis of respiratory muscles

C. tetani

occurs in dirt, dust, and in GI tract of humans who have eaten food contaminated with spores

tetanus

half of the cases result from puncture wounds: stepping in a nail, body piercing, tattooing, animal bites, splinters, and insect stings

tetanus prevention

active immunization

usually occurs within first year of life

booster dose are administered every 10 years neonatal version can be prevented by immunizing expectant mothers because of the toxoid crosses the placenta

tetanus treatment

treated by administering antitoxin 

antibody against tetanospamin

tetanus antitoxin

neutralizes any toxin not yet attached to a neuron

tetanus antibiotics

used to stop the production of more tetanospamin by C. tetani

neurotransmitters

chemicals stored in neurons and released when the cell is stimulated by a signal

Clostridium perfringens 

production of this neurotoxin that prevents acetylcholine release from the motor neurons at neuromuscular junctions, therefore inhibiting contraction

tetanus

neuromuscular disease caused by Clostridium tetani

tetanospasmin

neurotoxin that causes tetanus

gram negative diplococci

how Neisseria appears when gram stained and viewed microscopically

Polio

disabling and life-threatening disease caused by the poliovirus

spreads from person to person and can infect a person’s spinal cord causing paralysis

polio symptoms

1 out of 4 people with ____ will have flu-like symptoms:

sore throat

fever

tiredness

nausea

headache

stomach pain

post-polio syndrome

condition that can affect polio survivors’ decades after they recover from their initial poliovirus infection

some patients become wheelchair bound when they had not been before

polio transmission

infects only humans

more common in infants and young children

occurs at earlier age among children living in poor hygienic conditions

enters through mouth and multiplies in oropharynx and gastrointestinal tract

usually present in nasopharyngeal secretions, can be shed in stools

Creutzfeldt-Jakob disease (CJD)

rare, rapidly worsening brain disorder that causes unique changes in brain tissue and affects muscle coordination, thinking, and memory

CJD symptoms

severe mental deterioration

dementia

CJD

caused by an infectious agent that carries no nucleic acid —> prion disease

rabies and polio

caused by virus, carries DNA

meningitis

caused by staphylcoccus, contains DNA

ZIka virus (ZIKV)

mosquito-borne emerging flavivirus

caused by an infected Aedes mosquito

Zika virus symptoms

headache

fever

skin rashes

pink eye

conjunctivitis

muscle and joint pain

malaise

microcephaly

linked to Zika virus

deformed head within babies

zoonotic

viral disease affecting the central nervous system

once symptoms appear, 100% fatal

neglected tropical diseases (NTD)

rabies virus (RABV) 

prototype virus of the genus Lyssaviruse in the family Rhaboviridae

inoculated into muscle and subcutaneous tissues in the saliva of the biting animal

binds to nicotinic acetylcholine receptors at the neuromuscular junction and travels the spinal cord within axons of peripheral nerves

post-exposure prophylaxis (PEP)

emergency response to rabies exposure

prevents virus from entering the central nervous system, which would invariably result in death

consists of:

• extensive washing with water and soap for at least 15 minutes and local treatment of the wound

• course of potent and effective rabies vaccine that meets WHO standards

• administration of rabies immunoglobulin or monoclonal antibodies into the wound