Chapter 22 - Microbial Diseases of the Nervous System

MICR130 Final exam

Central Nervous System

brain and spinal cord

peripheral nervous system

nerves that branch from the CNS

Cerebrospinal Fluid

in the subarachnoid space

fluid used for cushioning and nourishment

Blood Brain Barrier

crucial immunological feature of the human CNS

very tightly regulates the movement of ions, molecules, and cells between the blood and brain

structural and functional roadblock to microorganisms

great protection from infection, but also limits diffiusion of certain drugs into CNS tissue

Meningitis

inflammation of the meninges

Meninges

protective membrane that covers the brian and spinal cord

Bacterial Meningitis

fever, headache, stiff neck, followed by nausea and vommiting

treatment: heavy administration of IV vancomycin

death due to shock and inflammaiton

• endotoxin from cell wall releases

Haemophilus Influenzae

normal throat microbiota

can enter the bloodstream

pathogenicity due to capsule antigen type b

occurs mostly in children

prevented by Hib Vaccine

45% of bacteiral meningitis cases

Neisseria Meningitidis (Meningococcal Meningitis)

40% of people are healthy nasopharyngeal carriers

begins as a throat infection and bacteremia

mortatlity is 80% without antibiotic therapy

outbreak common in dorms and military barracks

vaccination protects agianst some serogroups

Streptococcus Pneumonia (Pneumococcal Meningitis)

70% of people are healthy nasopharyngeal carriers

also causes pneumonia and otitis media (ear infection)

mortality is 8% in children and 22% in elderly

prevented by conjugated vaccine

Listeria Monocytogenes

Foodborne transmission

• commonly associated with deli meats and unpasteurized milk products

• bacteria can survive refirgeration

Very serious infection in pregnant women - crosses placenta and leads to stillbirht

bacteria can invade bloodstream, causing sepsis

reproduces in phagocytes

Tetanus

Caused by clostridium tetani

grows in deep wounds with anaerobic conditions

neurotoxin is released from dead cells

• causes muscle spasms

• death occurs from spasms of respiratory muscles

Prevented by vaccination with tetanus toxoid vaccine (DTaP)

• stimulates antibodies that neutralizees the toxin

• booster required every 10 years

Botulism

caused by clostridium botulinum

intoxication comes from ingesting the botulinum exotoxin

• blocks release of ACh causing flaccid paralysis

death comes from respiratory or cardiac failure

Infants: C. botulinum grows in teh intestine of infacnts due to a lack of intestinal microbiota

• assoiated with honey

prevented with proper canning and use of nitrates in food

no vaccine, but treatment with respiratory assitance and antibiotics

Leprosy (Hansen’s Disease)

Mycobacterium Leprae

Grows in peripheral nerve and skin cells

transmission requires prolonged contact with an infected person or the inhalation of secretions

caregivers of patients often become infected

Sent Lepers to colonies —> Kalaupapa in Molokai

Polio

Caused by Poliovirus

transmitted by the ingestion of water containing feces containing the virus

mainly affects children under 5

Vermia may occur; enters the CNS

• 1% of cases leads to irreversible paralysis

• destruction of motor nerve cells

• death from respiratory failure

Vaccine for all three serotypes

• Salk vaccine: inactivated vaccine; injectable

• Sabin Vaccine: attenuated live vaccine; oral; lifelong immunity

  • can be converted back into wild type

Rabies

caused by rabies virus

usually transmitted by the saliva of an animal bite

• in the US, silver-hair bats are most common

virus multiplies in skeletal muscels and travels through the PNS to brain cells, casuing encephalitis

• post exposure vaccination can be effective since there is time for the immune system to develop antibodies

once clinical symptoms show, virtually 100% fatal

Zika Virus disease

transmitted primarily through the bite of infected aedes spp. mosquito

other routes of transmission includes mother to child, sexual, blood transfusion

infection during pregnancy increase the risk of microcephaly in infants