diseases of the nervous system

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

M I C R O B I O L O G Ya n i n t r o d u c t i o n

ninth edition TORTORA FUNKE CASE

Part A

DISEASES OF THE NERVOUS

SYSTEM


How Microbes Enter the Nervous System

Skull or backbone fractures

Medical procedures

Along peripheral nerves

Blood or lymph


The Nervous System

Figure 22.1


Microbial Diseases of the Nervous System

Bacteria can grow in the cerebrospinal fluid in the

subarachnoid space of the CNS.

The blood brain barrier (capillaries) prevents passage

of some materials (such as antimicrobial drugs) into

the CNS.

Meningitis: Inflammation of meninges.

Encephalitis: Inflammation of the brain.


The Meninges and Cerebrospinal Fluid

Figure 22.2


Bacterial Meningitis

Fever, headache, and stiff neck

Followed by nausea and vomiting

May progress to convulsions and coma

Diagnosis by Gram stain or latex agglutination of CSF

Treated with cephalosporins


Bacterial Meningitis

Figure 22.3


Haemophilus influenzae Meningitis

Occurs mostly in children (6 months to 4 years).

Gram-negative aerobic bacteria, normal throat

microbiota

Capsule antigen type b

Prevented by Hib vaccine


Neisseria Meningitis, Meningococcal Meningitis

N. meningitidis

Gram-negative aerobic cocci, capsule

10% of people are healthy nasopharyngeal carriers

Begins as throat infection, rash

Serotype B is most common in the United States

Vaccination recommended for college students.


Neisseria Meningitis, Meningococcal Meningitis

Figure 22.4


Streptococcus pneumoniae Meningitis, Pneumococcal Meningitis

Gram-positive diplococci

70% of people are healthy nasopharyngeal carriers

Most common in children (1 month to 4 years)

Mortality: 30% in children, 80% in elderly

Prevented by vaccination


Listeriosis

Listeria monocytogenes

Gram-negative aerobic

rod

Usually foodborne; it can

be transmitted to fetus.

Reproduce in

phagocytes.

Figure 22.5


Tetanus

Clostridium tetani

Gram-positive, endospore-forming, obligate anaerobe

Grows in deep wounds.

Tetanospasmin released from dead cells blocks

relaxation pathway in muscles.

Prevention by vaccination with tetanus toxoid (DTP)

and booster (dT).

Treatment with tetanus immune globulin.


Tetanus

Figure 22.6


Botulism

Clostridium botulinum

Gram-positive, endospore-forming, obligate anaerobe

Intoxication comes from ingesting botulinal toxin.

Botulinal toxin blocks release of neurotransmitter

causing flaccid paralysis.

Prevention

Proper canning

Nitrites prevent endospore germination in sausages.


Botulism

Treatment: Supportive care and antitoxin.

Infant botulism results from C. botulinum growing

in intestines.

Wound botulism results from growth of C. botulinum

in wounds.


Botulism

Type A

60-70% fatality

Found in CA, WA, CO, OR, NM.

Type B

25% fatality

Europe and eastern United States

Type E

Found in marine and lake sediments

Pacific Northwest, Alaska, Great Lakes area


Leprosy

Mycobacterium leprae

Acid-fast rod that grows best at 30°C.

Grows in peripheral nerves and skin cells.

Transmission requires prolonged contact with an

infected person.

Tuberculoid (neural) form: Loss of sensation in skin

areas; positive lepromin test

Lepromatous (progressive) form: Disfiguring nodules

over body; negative lepromin test


Leprosy

Figure 22.9


Poliomyelitis

Poliovirus

Transmitted by ingestion.

Initial symptoms: Sore throat and nausea

Viremia may occur; if persistent, virus can enter the

CNS; destruction of motor cells and paralysis occurs in

<1% of cases.

Prevention is by vaccination (enhanced-inactivated

polio vaccine).


Poliomyelitis


Poliomyelitis

First vaccine made in Canada by Connaught Medical Research Laboratories


Poliomyelitis

Figure 22.11


Rabies Virus (Rhabdovirus)

Transmitted by animal bite.

Virus multiplies in skeletal muscles, then brain cells causing

encephalitis.

Initial symptoms may include muscle spasms of the mouth and

pharynx and hydrophobia.

Furious rabies: Animals are restless then highly excitable.

Paralytic rabies: Animals seem unaware of surroundings.

Preexposure prophylaxis: Infection of human diploid cells

vaccine.

Postexposure treatment: Vaccine plus immune globulin.



Figure 22.12



Figure 22.12

Negri Bodies in Neurons of Brain



Figure 22.13


Arboviral Encephalitis

Arboviruses are

arthropod-borne viruses

that belong to several

families.

Prevention is by

controlling mosquitoes.

Figure 22.14


Arboviral Encephalitis

Encephalitis Reservoir Mosquito vector U.S. distribution

Western equine Birds, horses Culex

Eastern equine Birds, horses Aedes, Culiseta

St. Louis Birds Culex

California Small mammals Aedes

West Nile Birds,

mammalsCulex, Aedes


Cryptococcus Neoformans Meningitis (Cryptococcosis)

Figure 22.15


Cryptococcus Neoformans Meningitis (Cryptococcosis)

Soil fungus associated with pigeon and chicken

droppings.

Transmitted by the respiratory route; spreads through

blood to the CNS.

Mortality up to 30%.

Treatment: Amphotericin B and flucytosine.


African Trypanosomiasis

Trypanosoma brucei gambiense infection is chronic

(2 to 4 years).

T. b. rhodesiense infection is more acute (few months).

Transmitted from animals to humans by tsetse fly.

Prevention: Elimination of the vector.

Treatment: Eflornithine blocks an enzyme necessary

for the parasite.

Parasite evades the antibodies through antigenic

variation.


African Trypanosomiasis

Figure 22.16


Naegleria fowleri

Protozoan

infects nasal

mucosa from

swimming

water.

Figure 22.17


Transmissible Spongiform Encephalopathies

Caused by prions

Sheep scrapie

Creutzfeldt-Jakob disease

Kuru

Bovine spongiform encephalopathy

Transmitted by ingestion or transplant or inherited.

Chronic and fatal


Transmissible Spongiform Encephalopathies

Figure 22.18

diseases of the nervous system

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