Microbiology Ch. 22: Microbial Diseases of the Nervous System

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Tortora; Microbiology 265 Ch. 22: Microbial Diseases of the Nervous System

Central Nervous System (CNS)

consists of the brain and spinal cord

Peripheral Nervous System (PNS)

consists of all the nerves that branch off from the brain and spinal cord

meningitis

general term for the inflammation of the meninges

*The meninges are the dura mater, arachnoid mater, and the pia mater.

encephalitis

general term for the inflammation of the brain itself

meningoencephalitis

general term for the inflammation of the brain and the meninges

Meningitis and Encephalitis

BACTERIAL DISEASES:
Haemophilus influenzae meningitis
Meningococcal meningitis
Pneumococcal meningitis
Listeriosis

FUNGAL DISEASE:
Cryptococcosis

PROTOZOAN DISEASES:
Primary amebic meningoencephalitis
Granulomatous amebic encephalitis

BACTERIAL Diseases that can cause meningitis and/or encephalitis

Haemophilus influenzae meningitis
Meningococcal meningitis
Pneumococcal meningitis
Listeriosis

*Diagnosis of bacterial meningitis requires a sample of cerebrospinal fluid obtained by a spinal tap. A Gram stain is often useful.

FUNGAL Diseases that can cause meningitis and/or encephalitis

Cryptococcosis

PROTOZOAN Diseases that can cause meningitis and/or encephalitis

Primary amebic meningoencephalitis
Granulomatous amebic encephalitis

Haemophilus influenzae meningitis

PATHOGEN: Haemophilus influenzae
MORPHOLOGY: Gram-negative rod

PORTAL OF ENTRY: Respiratory tract
METHOD OF TRANSMISSION: Endogenous infection; aerosols

TREATMENT: Cephalosporin
Prevention: Capsular Hib vaccine

Meningococcal meningitis

PATHOGEN: Neisseria meningitidis
MORPHOLOGY: Gram-negative diplococcus

PORTAL OF ENTRY: Respiratory tract
METHOD OF TRANSMISSION: Aerosols

TREATMENT: Cephalosporin
Prevention: Capsular vaccine against serotypes A, C, Y W- 135

Pneumococcal meningitis

PATHOGEN: Streptococcus pneumoniae
MORPHOLOGY: Gram-positive cocci

PORTAL OF ENTRY: Respiratory tract
METHOD OF TRANSMISSION: Aerosols

TREATMENT: Cephalosporin
Prevention: Polysaccharide vaccine

Listeriosis

PATHOGEN: Listeria monocytogenes
MORPHOLOGY: Gram-positive facultative anaerobe

PORTAL OF ENTRY: Mouth
METHOD OF TRANSMISSION: Foodborne infection

TREATMENT: Penicillin G
Prevention: Pasteurizing and cooking food

Cryptococcosis

PATHOGEN: Cryptococcus neoformans
C. grubii
C. gattii

PORTAL OF ENTRY: Respiratory tract
METHOD OF TRANSMISSION: Inhaling soil contaminated with spores

TREATMENT: Amphotericin B, flucytosine

*The disease is transmitted mainly by the inhalation of dried, contaminated droppings - esp. of pigeons.

Primary amebic meningoencephalitis

PATHOGEN: Naegleria fowleri
PORTAL OF ENTRY: Mucous membrane

METHOD OF TRANSMISSION: Swimming

TREATMENT: Amphotericin B

These protozoa are found in freshwater. The most common victims are children who swim in ponds or streams.

Granulomatous amebic encephalitis

PATHOGEN: Acanthamoeba spp;
Balamuthia mandrillaris

PORTAL OF ENTRY: Mucous membranes
METHOD OF TRANSMISSION: Swimming

TREATMENT: Amphotericin B

These protozoa are found in freshwater. The most common victims are children who swim in ponds or streams.

Microbial Diseases with Neurological Symptoms or Paralysis

BACTERIAL DISEASES:
Tetanus
Botulism
Leprosy

VIRAL DISEASES:
Poliomyelitis
Rabies

PROTOZOAN DISEASE:
African trypanosomiasis

PRION DISEASES:
Creutzfeldt-Jakob Disease
Kuru

BACTERIAL Diseases with Neurological Symptoms or Paralysis

Tetanus
Botulism
Leprosy

VIRAL Diseases with Neurological Symptoms or Paralysis

Poliomyelitis
Rabies

PROTOZOAN Disease with Neurological Symptoms or Paralysis

African trypanosomiasis

PRION Diseases with Neurological Symptoms or Paralysis

Creutzfeldt-Jakob Disease
Kuru

Tetanus

PATHOGEN: Clostridium tetani
MORPHOLOGY: Gram-positive rod

SYMPTOMS: Lockjaw; muscle spasms
METHOD OF TRANSMISSION: Puncture wound

TREATMENT: Tetanus immune globulin (TIG); antibiotics
Prevention: Toxoid vaccine (DTaP, Td)

Botulism

PATHOGEN: Clostridium botulinum
MORPHOLOGY: Gram-positive rod

SYMPTOMS: Flaccid paralysis
METHOD OF TRANSMISSION: foodborne intoxication

TREATMENT: Antitoxin
Prevention: Proper canning of foods; infants should not have honey

Leprosy

PATHOGEN: Mycobacterium leprae
MORPHOLOGY: Acid-fast rod. Aerobic, intracellular bacterium

SYMPTOMS: Loss of sensation in skin; disfiguring nodules
METHOD OF TRANSMISSION: Probably prolonged contact with contaminated secretions

TREATMENT: Dapsone, rifampin, clofaximine
Prevention: Possibly BCG vaccine

Poliomyelitis

PATHOGEN: Poliovirus
SYMPTOMS: Headache, sore throat, stiff neck; paralysis if motor nerves infected

METHOD OF TRANSMISSION: Ingesting contaminated water (fecal-oral route)

TREATMENT: Mechanical breathing aid (iron lung)
Prevention: Inactivated polio vaccine (E-IPV)

Rabies

PATHOGEN: Lyssavirus, including rabies virus
SYMPTOMS: Fatal infection; early symptoms include agitation, muscle spasms, difficulty swallowing

METHOD OF TRANSMISSION: Animal bite

TREATMENT: Postexposure treatment: rabies immunoglobulin plus vaccine (RIG)
Prevention: Human diploid cell vaccine for high-risk individuals; vaccination of domestic animals

African trypanosomiasis

PATHOGEN: Trypanosoma brucei rhodiense,
T. b. gambiense

SYMPTOMS: Fatal infection; early symptoms (headache, fever) progress to coma
METHOD OF TRANSMISSION: Tsetse fly

TREATMENT: Suramin; pentamidine
Prevention: Vector control

AKA "African sleeping sickness"

Creutzfeldt-Jakob disease

PATHOGEN: Prion

SYMPTOMS: Fatal infection; neurologic symptoms include trembling
METHOD OF TRANSMISSION: Inherited; ingested; transplants

TREATMENT: none
Prevention: none

*Mad cow disease

Kuru

PATHOGEN: Prion

SYMPTOMS: Fatal infection; neurologic symptoms include trembling
METHOD OF TRANSMISSION: Contact or ingestion

TREATMENT: none
Prevention: none

Practice Test Questions

...

A 30-yr old female was hospitalized after she experienced convulsions. On examination she was alert and oriented and complained of a fever, headache, and stiff neck. Her symptoms could be due to all of the following except...

A) Clostridium botulinum
B) Listeria monocytogenes
C) Naegleria fowleri
D) Streptococcus pneumoniae
E) None of the above

A) Clostridium botulinum




The prodromal symptoms of meningitis are: fever, headache, and stiff neck.
Also, meningitis is a general term for the inflammation of the meninges.

A 30-yr old female was hospitalized after she experienced convulsions. On examination she was alert and oriented and complained of a fever, headached, and stiff neck. Which of the following is most likely to provide rapid identification of the cause of her symptoms?

A) Gram stain of cerebrospinal fluid
B) Gram stain of throat culture
C) Biopsy of brain tissue
D) Check serum antibodies
E) None of the above; it can't be diagnosed

A) Gram stain of cerebrospinal fluid



Suspicion: bacterial meningitis
The quickest way to determine the causative agent of the bacterial meningitis is with a gram stain of the CSF.

All of the following are true about the lepromin test except...

A) It consists of human tissue extract
B) It detects the presence of anti-M. leprae antibodies
C) It is negative in the lepromatous form
D) It consists of M. leprae
E) None of the above

A) It consists of human tissue extract

A 1-yr old female was hospitalized with fever, lethargy, and rash. Gram-negative, oxidase-positive cocci were cultured from her cerebrospinal fluid. Her symptoms were caused by...

A) A prion
B) Clostridium tetani
C) Mycobacterium leprae
D) Neisseria meningitidis
E) Rabies

D) Neisseria meningitidis


Gram-negative cocci

Which of the following vaccines is a cause of the disease it is designed to prevent?

A) Tetanus toxoid vaccine
B) Oral polio vaccine
C) Inactivated polio vaccine
D) Haemophilus influenzae capsule vaccine

B) Oral polio vaccine



On rare occasions, the attenuated strain used in the vaccine may revert to a virulent strain and transmit the disease.

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