Both the brain and the spinal cord are covered and protected
by three continuous membranes called meninges

outermost meninges

middle meninges

innermost meninges

Between the pia mater and arachnoid
membranes

an adult has 100 to 160 ml of cerebrospinal fluid (CSF) circulating

...

inflammation of the meninges

inflammation of the brain

both
the brain and the meninges are affected, the inflammation

it is lipid soluble

the brain

is probably
much more common than bacterial meningitis but tends
to be a mild disease.

Most cases occur in the summer and fall
months and are usually caused by a varied group of viruses
termed enteroviruses

grow well in the throat and intestinal tract; they are responsible
for an assortment of mostly minor diseases.

Viral meningitis
can also be an occasional complication of viral infections such
as mumps, chickenpox, and influenza

caused by Haemophilus influenzae type B,

about 80% of the cases are
now caused by Neisseria meningitidis and Streptococcus pneumoniae.

All three of these pathogens possess a capsule that
protects them from phagocytosis as they replicate rapidly in the
bloodstream, from which they might enter the cerebrospinal
fluid

is an aerobic, gram-negative bacterium
that is a common member of the normal throat microbiota

In addition to causing meningitis, it is also frequently
a cause of pneumonia (page 693), otitis media (page 685),
and epiglottitis

The carbohydrate capsule of the bacterium is
important to its pathogenicity, especially those bacteria with
capsular antigens of type b. (Strains that lack a capsule are called
nontypable.)

caused by Neisseria meningitidis
(the meningococcus). This is an aerobic, gram-negative bacterium
with a polysaccharide capsule that is important to its virulence

A case of meningococcal meningitis
typically begins with a throat infection, leading to bacteremia
and eventually meningitis.

Streptococcus pneumoniae, like H. influenzae, is a common inhabitant
of the nasopharyngeal region.

About 70% of the general population are healthy carriers

The pneumococcus, so called because
it is best known as a cause of pneumonia (Chapter 24), is a
gram-positive, encapsulated diplococcus

is a gram-positive rod known to cause
stillbirth and neurological disease in animals long before it was
recognized as causing human disease

the organism is mostly foodborne.
It is frequently isolated from a wide variety of foods; ready-toeat
deli meats and dairy products have been involved in several
outbreaks.

L. monocytogenes is one of the few pathogens capable
of growth at refrigerator temperatures, which can lead to an increase
in its numbers during a food’s shelf life

clear CSF;Neisseria meningitidis

L. monocytogenes is one of the few pathogens capable
of growth at refrigerator temperatures, which can lead to an increase
in its numbers during a food’s shelf life

CSF

Clostridium tetani, is an obligately
anaerobic, endospore-forming, gram-positive rod

symptoms of tetanus are caused by an extremely potent
neurotoxin that is released upon death and lysis
of the growing bacteria

tetanospasmin

is a toxoid,
an inactivated toxin that stimulates the formation of antibodies
that neutralize the toxin produced by the bacteria

temporary immunity can be
conferred by tetanus immune globulin (TIG), prepared from the
antibody-containing serum of immunized humans

Made by inoculating horses, antisera were very effective in
lowering the incidence of tetanus in injured people.

To minimize the production of more toxin, damaged
tissue that provides growth conditions for the pathogen
should be removed, a procedure called debridement (sounds
like “de-breed-ment”), and antibiotics should be administered

toxin

a form of food poisoning, is caused by Clostridium
botulinum, an obligately anaerobic, endospore-forming grampositive
rod found in soil and many aquatic sediments.

microorganism produces an exotoxin.

This neurotoxin
is highly specific for the synaptic end of the nerve, where
it blocks the release of acetylcholine, a chemical necessary for
transmitting nerve impulses across synapses

botulism undergo a progressive
flaccid paralysis for 1 to 10 days and may die from respiratory
and cardiac failure

flaccid paralysis

nitrates added

is the more formal
name for leprosy;

If the immune system fails to control the
disease, the result is lepromatous (progressive) leprosy

The standard diagnostic test for leprosy

mice and armadillos are used to grow M. leprae

consists of viruses of all three types
that have been inactivated (killed) by treatment with formalin.

Vaccines of this types, called inactivated polio vaccines (IPV)

contains
living, attenuated (weakened) strains of the virus in a suspension
that is ingested

is more commonly called oral polio vaccine (OPV).
It usually contains the three types of polio virus (trivalent,
tOPV).

vaccine for polio

Improved sanitation delayed
exposure to polioviruses in feces until after the protection provided
by maternal antibodies had waned. At one time, exposure
to the poliovirus was frequent (and is still so today in parts of the
world with poor sanitation).

Infants were usually exposed to poliovirus
while still protected by maternal antibodies.

The result was
usually an asymptomatic case of the disease and a lifelong immunity.

When infection is delayed until adolescence or early adulthood,
the paralytic form of the disease appears more frequently

(the word is from the Latin for rage or madness) is a disease
that almost always results in fatal encephalitis

The causative
agent is the rabies virus, a member of the genus lyssavirus having
a characteristic bullet shape

which there is only minimal excitability. This form is especially
common in cats

meaning a series of antirabies vaccine and immune
globulin injections

rabies vaccine

vaccines are
administered in a series of four injections at intervals during
a 14-day period

Passive immunization is provided simultaneously
by injecting human rabies immune globulin (RIG) that has
been harvested from people who are immunized against rabies

such as caged
chickens, are tested periodically for antibodies to arboviruses.
This gives health officials information on the incidence and types
of viruses in their area

caused by fungi of the genus Cryptococcus.
They form spherical cells resembling yeasts, reproduce by
budding, and produce extremely heavy polysaccharide capsules

bird droppings

sleeping sickness, is a protozoan disease
that affects the nervous system

disease is caused by two subspecies of Trypanosoma
brucei that infect humans: Trypanosoma brucei gambiense and
Trypanosoma brucei rhodesiense

These protozoans are flagellates (see Figure 23.23
on page 667 for the appearance of a similar organism) that are
spread by tsetse fly vectors

Naegleria fowleri is a protozoan (ameba) that causes a neurological
disease, primary amebic meningoencephalitis (PAM)

swim in warm ponds or streams. The organism initially infects
the nasal mucosa and later penetrates to the brain and proliferates,
feeding on brain tissue

tsetse fly species that inhabits stream vegetation

abnormally folded protein

mad cow disease

a strong solution of sodium hydroxide combined
with extended autoclaving at 134°C.