CNS Diseases Chapter 22 MT Presentation 2021 PDF

Microbial Diseases of the Nervous System Dr. Marina Tediashvili University of Georgia © 2013 Pearson Education, Inc.  The human nervous system...

Microbial Diseases of the Nervous System Dr. Marina Tediashvili University of Georgia © 2013 Pearson Education, Inc.  The human nervous system Brain Central nervous system (CNS) Spinal cord Peripheral nervous system (PNS) © 2013 Pearson Education, Inc.  The Nervous system  The human nervous system is organized into two divisions: - central nervous system (brain and spinal cord) - peripheral nervous system ( all nerves that branch off from the brain and spinal cord)  Strongly protected from accident and infection by bone and other structures.  Pathogens that are circulating in the bloodstream usually cannot enter the brain and spinal cord because of the blood-brain barrier © 2013 Pearson Education, Inc.  The Nervous system  Brain and the spinal cord are covered and protected by three continuous membranes - meninges - Dura mater: outermost layer - Arachnoid mater: middle layer - Pia mater: innermost layer  - Subarachnoid space contains cerebrospinal fluid (CSF)- 100 to 160 ml in an adult  Blood- brain barrier - Certain capillaries are more selective in passing materials - permit some substances to pass from the blood into the brain but restrict others - Drugs cannot cross unless they are lipid-soluble - Special transport system for glucose and aminoacids © 2013 Pearson Education, Inc.  The meninges and cerebrospinal fluid. Skull bone Cerebrum Subarachnoid space (contains Skull cerebrospinal fluid) Dura mater bone Arachnoid mater Cranial meninges Pia mater Blood vessel Cerebrum Cerebellum Spinal cord Dura mater Arachnoid Spinal mater meninges Pia mater Subarachnoid space of spinal Subarachnoid space (contains cerebrospinal cord fluid) Central canal © 2013 Pearson Education, Inc. Damage of nervous system  Damage Spinal cord and brain can lead to deafness, blindness, learning disabilities, paralysis and death  Cerebrospinal fluid is especially vulnerable because it lacks many of the defenses found in the blood  Pathogens causing diseases of the nervous system often have special virulence characteristics - can begin replicating in a peripheral nerve and gradually move into the brain and spinal cord © 2013 Pearson Education, Inc. Inflammation of Nervous System  Bloodstream and lymphatic system- most common routes of CNS invasion when inflammation alters permeability of the blood- brain barrier.  Meningitis: inflammation of meninges  Encephalitis: inflammation of the brain  Meningoencephalitis: inflammation of both  Meningitis can be caused by different types of pathogens: viruses, bacteria, fungi, and protozoa © 2013 Pearson Education, Inc. Bacterial Meningitis  Initial symptoms of fever, headache, and stiff neck  Followed by nausea and vomiting  May progress to convulsions and coma  Three main causes : Streptococcus pneumoniae Neisseria meningitidis Haemophilus inluenzae type B  Opportunistic pathogens Listeria monocytogelles, group B streptococci, staphylococci, some gram-negative bacteria  Diagnosis: investigation of CSF by Gram stain and latex agglutination © 2013 Pearson Education, Inc. Spinal tap (lumbar puncture) Spinal needle is inserted, usually between the fourth and fifth lumbar vertebrae Cerebrospinal fluid Spinal cord Fourth lumbar vertebra L4 Cauda equina L5 Sample of cerebrospinal Longitudinal fluid section of the spine Fifth lumbar © 2013 Pearson Education, Inc. vertebra Haemophilus influenzae Meningitis  Haemophilus refers to the need for factors in blood for growth (hemo = blood; philus = loving)  Gram-negative aerobic bacteria, normal throat microbiota  Meningitis occurs mostly in children (6 months to 4 years)  Causes also frequently pneumonia, otitis media, and epiglottitis.  Carbohydrate capsule antigen type b ( Hib)  Prevented by Hib vaccine © 2013 Pearson Education, Inc. Haemophilus influenzae © 2013 Pearson Education, Inc. Neisseria Meningitis  Also called meningococcal meningitis  Caused by N. meningitidis  Gram-negative, aerobic cocci with a capsule  five capsular serotypes - B, C, Y, W-135  Serotype B & C in United States  Serotype A in Africa  Throat infection, rash bacteriemia meningitis - very rapidly produced endotoxin  Reservoir of infection - healthy nasopharyngeal carriers (10% )  Occurs in children under 2 years  Mortality rates (without chemotherapy) - 80%  Vaccination (A, C, Y, W-135 capsule) recommended for college students © 2013 Pearson Education, Inc.  Neisseria meningitis N. meningitidis Cilia N. meningitidis © 2013 Pearson Education, Inc. Streptococcus pneumoniae Meningitis  Also called pneumococcal meningitis  Caused by S. pneumoniae (a gram-positive diplococcus)  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 - a conjugated vaccine S. pneumoniae © 2013 Pearson Education, Inc.  Listeriosis  Caused by Listeria monocytogenes  Gram-positive aerobic rod  two basic forms: - in infected adults - infection of the fetus and newborn  Usually foodborne (ready-to-eat meats and dairy products);  Capable of growth at refrigerator temperatures  Infant mortality rate is about 60%  Reproduce in phagocytes  Spread phagocyte-to-phagocyte  Penicillin G is the antibiotic of choice for treatment. © 2013 Pearson Education, Inc. Figure 22.5 Cell-to-cell spread of Listeria monocytogenes, the cause of listeriosis. Listeria monocytogenes Macrophage Macrophage Pseudopod © 2013 Pearson Education, Inc. Diagnosis and Treatment of the Most Common Types of Bacterial Meningitis  CSF Sample obtained by a spinal tap, or lumbar puncture  Gram stain  Culture: made from the fluid - pathogens are very sensitive to storage and temperature change  Bacterial meningitis develops rapidly and is life-threatening  Chemotherapy is usually initiated before pathogen’s identification is completed  Broad spectrum third -generation cephalosporins © 2013 Pearson Education, Inc.  Tetanus  Clostridium tetani - Gram-positive, endospore-forming, obligate anaerobe - Found in soil contaminated with animal feces - Grows in deep wounds  Tetanospasmin released from dead cells - blocks relaxation pathway in muscles - both opposing sets of muscles contract, resulting in the characteristic muscle spasms –spastic paralysis  The bacteria do not spread from the infection site, and there is no inflammation.  Treatment with tetanus immune globulin (TIG) © 2013 Pearson Education, Inc.  An advanced case of tetanus Opisthonos –a condition when spasms of the back muscles cause the head and heels to bow backward © 2013 Pearson Education, Inc. Treatment and prevention of tetanus  Prevention by vaccination with tetanus toxoid (DTaP) and booster (Td)  People with extensive injuries who have previously had three or more doses of toxoid within the past 10 years considered to be protected - no action.  In patients with unknown or low immunity, Tetanus immunoglobulin (TlG) is given to provide temporary protection.  In addition, the first of a toxoid series is administered to provide more permanent immunity  Debridement: removal of damaged tissue that provides growth conditions for the pathogen © 2013 Pearson Education, Inc. Botulism  First described in early 1800s as the sausage disease (botulus is the Latin word for sausage).  Clostridium botulinum -Gram-positive, endospore- forming, obligate anaerobe  Exotoxin - neurotoxin produced in anaerobic environments (e.g. sealed cans)  Intoxication comes from ingesting botulinal toxin - highly specific for synaptic end of the nerve - blocks the release of acetylcholine, a chemical transmitting nerve impulses across synapses © 2013 Pearson Education, Inc. Botulinal Types  Several serological types of the botulinal toxin produced by different strains  Type A toxin – produced by proteolytic strains  most virulent (mortality rate 60-70% in untreated cases) - type A endospore - most heat resistant - found in the US -California, Washington, Colorado  Type B toxin ( mortality rate 25% ) -most European outbreaks, eastern United States  Type E toxin - produced by strains found in marine or lake sediments, outbreaks commonly involve seafood - less strictly anaerobic, non-proteolitic - outbreaks in Northern US- Alaska, Great Lakes area etc © 2013 Pearson Education, Inc. Botulism  Flaccid paralysis develops in 1-10 days - initial symptoms: double or blurred vision, difficulty swallowing and general weakness - death from respiratory and cardiac failure  Infant botulism results from C. botulinum growing in intestines - ingestion of soil and other materials contaminated with the endospores of the organism - many reported cases associated with honey.  Wound botulism results from growth of C. botulinum in wounds © 2013 Pearson Education, Inc. Botulism: treatment and prevention  Prevention  Boiling of food  Proper canning  Nitrites prevent endospore germination in sausages  Botulinal toxin is not formed in acidic foods ( pH< 4.7)  not to feed honey to infants under I year of age;  Treatment: supportive care and antitoxin - horse antisera / antitoxin used in adults may cause serious side effects ( serum sickness and anaphylaxis)  safer treatment for infant botulism- intravenous human immune globulin © 2013 Pearson Education, Inc. Diagnosis of Botulism  Botulism is diagnosed by  Inspection of left over inoculating mice with samples food - from patient’s serum, stool, or vomitus specimens - suspected food  Mice are immunized with type A, B, or E antitoxin  Monitoring of survival © 2013 Pearson Education, Inc. Use of Botox  Botulism toxin (Botox) has therapeutic uses for a number of medical conditions - chronic headaches - relieving painful muscle contractions in cerebral palsy, Parkinson disease, and multiple sclerosis - involuntary eyelid twitching (blepharospasm)  Application foe cosemtic purposes: - periodic local injections of Botox for elimination of forehead wrinkles (worry lines). © 2013 Pearson Education, Inc. Leprosy  Also called Hansen’s disease  Caused by Mycobacterium leprae - Acid-fast rod , grows best at 30°C - very long generation time ( up to12 days).  Preference for the outer, cooler portions of the human body. Tuberculoid (neural) leprosy  Grows in peripheral nerves and skin cells  Transmission requires prolonged contact with an infected person © 2013 Pearson Education, Inc. Lepromatous (progressive) leprosy Leprosy  Tuberculoid (neural) form: loss of sensation in skin areas; positive lepromin test - occurs in people with effective immune reactions; recovery sometimes occurs spontaneously  Lepromatous (progressive) form: disfiguring nodules over body; negative lepromin test - the least effective cell-mediated immune response, - Mucous membranes of the nose are affected - a lion-faced appearance  Patients with lepromatous leprosy shed large numbers in their nasal secretions  Complications, such as tuberculosis © 2013 Pearson Education, Inc. Leprosy– diagnostics, treatment  M. leprae has never been grown on artificial media.  Skin biopsy sample taken from the margin of an active lesion. - looking for characteristic tissue damage and identifying acid-fast bacilli within nerves  Armadillos - a useful way to culture the leprosy bacillus- they have a body temperature of 30 - 35°  Dapsone (a sulfone drug), rifampin, and clofazimine, ( fatsoluble dye) - principal drugs used for treatment in combination  1998- commercially available vaccine in India © 2013 Pearson Education, Inc. Poliomyelitis (Polio)  Poliovirus - ss RNA virus  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