Microbiology Ch. 26: Nervous System Infections
Rabies: Prevention
Avoid suspect animals; Immunize pets; Vaccine is available for at-risk individuals
Leprosy
Tuberculoid Leprosy; Lepromatous Leprosy
Variant Creutzfeldt-Jakob Disease: Virulence Factors
Turn normal prions into abnormal form
Poliomyelitis: Prevention
Two effective vaccinations are available: Salk Vaccine, Sabin Vaccine
Sabin Vaccine
Attenuated, Oral Polio Vaccine (OPV)
Classes of Neurons
1. Sensory (afferent) neurons conduct signals from receptors to the CNS: Peripheral Nervous System 2. Interneurons (association neurons) are confined to the CNS: Central Nervous System 3. Motor (efferent) neurons conduct signals from the CNS to effectors such as muscles and gland: Peripheral Nervous System
Leprosy: Incubation Period
3 months to 20 years; Usually 3 years
Poliomyelitis: Incubation Period
7 to 14 days
Spongiform Encephalitis
A class of diseases that include Scrapie and "Mad Cow" disease; Leaves brain of victims full of holes; Can occur spontaneously in the elderly; Human can contract by eating meat from infected cattle
Viral Encephalitis
A secondary infection that can complicate issues; Arbovirus
Viral Encephalitis: Signs and Symptoms
Abrupt onset, fever, headache, vomiting, disorientation, paralysis, seizures, deafness, coma
Viral Meningitis: Signs and Symptoms
Abrupt onset, fever, severe headache, stiff neck, often vomiting; Sometimes sore throat, rash, or chest pain; "Aseptic meningitis", usually milder than those of bacterial or fungal
Prion Disease
An infectious protein; Spongiform Encephalitis; Variant Creutzfeldt-Jakob Disease
Botulism
An intoxication with three manifestations: Foodborne, Infant, and Wound
Poliomyelitis: Treatment
Artificial ventilation for respiratory paralysis (iron lung); Physical therapy and rehabilitation
Leprosy: Prevention
BCG vaccine provides some protection; Prevent infections by avoiding exposure to pathogen
Leprosy: Diagnosis
Based on signs and symptoms; Confirmed by the presence of acid-fast bacilli in samples
Bacterial Meningitis: Diagnosis
Based on symptoms and culturing bacteria from CSF
Phosphorylcholine
Binds to cell wall
Septicemia
Blood poisoning
Botulism: Signs and Symptoms
Blurred or double vision, weakness, nausea, vomiting, diarrhea, or constipation; generalized paralysis and respiratory insufficiency
Central Nervous System
Brain, Spinal Cord
Portals of Infection of the CNS
CNS is an axenic environment, it has no normal microbiota; Pathogens may reach the CNS several ways: breaks in the bones and meninges, medical procedures, travel in peripheral neurons to the CNS, infect and kill cells of the meninges causing meningitis, inflammation can alter the permeability of the blood brain barrier
Infant Botulism
Can occur when you feed infants honey; Results from the ingestion of endospores; Nonspecific symptoms
Viral Meningitis: Diagnosis
Characteristic signs and symptoms in the absence of bacteria in the CSF
Variant Creutzfeldt-Jakob Disease: Causative Agent
Caused by abnormal form of prion protein
Cell Blebbing
Cell sheds membrane causing an inflammatory response
Subdivisions of the Nervous System
Central Nervous System (CNS); Peripheral Nervous System (PNS)
Viral Encephalitis: Prevention
Chicken sentinels to warn of arbovirus epidemics; Insecticides and other anti-mosquito measures; Purifying and cleansing water; Vaccine against easter equine approved for use in horses, has been used to protect emus; Equine form generally infects 1-2 weeks before first human cases
Microglia
Clean up debris and damaged neurons
Botulism: Pathogenesis
Clostridium botulinum endospores germinate and the resulting vegetative cells multiply in favorable environments, releasing botulinum toxin. The toxin may consumed in food (foodborne), produced by cells in the intestinal tract (intestinal or infant), or made by cells infecting a wound (wound). Circulating toxin binds to motor nerves and stops the transmission of nerve signals to the muscles, producing flaccid paralysis
Botulism: Causative Agent
Clostridium botulinum, an anaerobic, Gram positive, endospore-forming, rod shaped bacterium
Viral Meningitis: Enterovirus
Common means of transmission is through the intestinal tract
Wound Botulism
Contamination of a wound by endospores; Symptoms similar to foodborne botulism
Cryptococcal Meningoencephalitis: Causative Agent
Cryptococcus neoformans: basidiomycete yeast, spherical single cell; Cryptococcus gattii: encapsulated yeasts
Botulism: Treatment
Depends on the type, but may involve intravenous administration of botulism immune globulin or antimicrobial drugs and artificial respiration, washing of intestinal tract to remove Clostridium
Cryptococcal Meningoencephalitis: Diagnosis
Detection of fungal antigen in CSF
Rabies: Signs and Symptoms
Fever, headache, nausea, vomiting, sore throat, cough at onset; Later spasms of the muscles of mouth and throat, coma, and death; Characteristic neurological signs if virus reaches CNS: hydrophobia, seizures, hallucinations, paralysis
Leprosy: Epidemiology
Direct contact with M. leprae from mucous membrane secretions
Rabies: Pathogenesis
During incubation period, virus multiplies at site of bite, then travels via nerves to the central nervous system; it multiplies outward via multiple nerves to infect heart and other organs
Viral Encephalitis: Incubation Period
First symptoms within a few days; Symptoms often within the first week
Botulism: Epidemiology
Endospores widespread in soil, aquatic sediments, and dust. Foodborne is often due to consuming an improperly processed home-canned low-acid food. Intestinal or infant typically occurs in infants, and sometimes involves endospore-containing honey. Wound often involves injection-drug abuse; ~ 30 cases of foodborne and wound per year in U.S.; Infant is the most common form in the U.S.
Viral Meningitis: Epidemiology
Enteroviruses are transmitted by the fecal-oral route, mainly in summer and early fall, also spread by respiratory droplets
Mycoses of the Nervous System
Fungal diseases; Spread from the lungs to the CNS via the blood; Mushroom toxins can produce hallucinations and neurological problems; May also produce fungal meningitis
Neisseria meningitidis
Gram negative, diplococci; Bacterium- meningococcal; Polysaccharide capsule; Serotype: A, B, C, Y; Resists lytic enzymes by phagocytes; Carried by neutrophils and macrophages; Cell Blebbing; Septicemia; Non-blanching rash; Glass Test
Haemophilus influenzae
Gram negative; Pleomorphic bacillus; Obligate parasite of humans and some animals; Presence of capsule resists phagocytosis; Different strains distinguished by capsular antigens; Prior to vaccination most disease caused by H. influenzae type b; Require NDA+ and heme for growth; Unencapsulated normal microbiota in nasopharynx; Grow on blood agar; Hemolytic zone
Streptococcus pneumoniae
Gram positive, Coccus; Leading cause of meningitis in adults; Opportunistic pneumococci; Moves into meninges via blood; Polysaccharide cell wall; Phosphorylcholine
Bacterial Meningitis: Epidemiology
H. influenzae was leading cause of bacterial meningitis prior to vaccination; S. pneumoniae and N. meningitidis are now most prevalent; Meningococcal meningitis can become epidemic: spread among individuals in barracks and dorms
Viral Meningitis: Prevention
Handwashing, avoiding crowded swimming pools during enterovirus outbreak
Poliomyelitis: Signs and Symptoms
Headache, fever, stiff neck, nausea, pain, muscle spasm, followed by paralysis; Asymptomatic infections: almost 90% of cases symptoms, Minor: nonspecific symptoms, Nonparalytic: muscle spasms and back pain, Paralytic: produces paralysis, Postpolio Syndrome: can be debilitating
Cryptococcal Meningoencephalitis: Signs and Symptoms
Headache, vomiting,confusion, and weight loss; Slight or no fever; Symptoms may progress to seizures, paralysis, coma, and death
Poliomyelitis: Diagnosis
Identification of virus in throat or feces
Rabies: Treatment
Immediately wash wound with soap and water and apply antiseptic; Inject rabies vaccine and human rabies antiserum as soon as possible. No effective treatment once symptoms begin
Salk Vaccine
Inactivated Polio Vaccine (IPV)
How does bacteria cause diseases in the nervous system?
Infect cells of the nervous system; Bacteria growing elsewhere release toxins that affect neurons
Cryptococcal Meningoencephalitis: Pathogenesis
Infection starts in lung; Encapsulated organisms multiply, enter bloodstream, and are carried to various parts of the body; Phagocytosis inhibited; Meninges and adjacent brain tissue become infected
Cryptococcal Meningoencephalitis: Epidemiology
Inhalation of material contaminated with the fungus; Other sources; Most people resistant to the disease; Lives in soil, tree sap, bird feces; Spread inhibited by phagocytosis; Defining opportunistic infection for AIDS
Variant Creutzfeldt-Jakob Disease: Signs and Symptoms
Insomnia, weight loss, and memory failure; Progressive worsening of muscle control
Leprosy: Pathogenesis
Invasion of small nerves of skin; multiplication in macrophages; course of disease depends on immune response of host; in tuberculoid leprosy, activated macrophages limit the growth of the bacterium but the damage to infected nerve cells leads to disabling deformities in lepromatous leprosy, cell-mediated immunity fails, allowing unrestrained growth of M. leprae
Why is it important that the cells forming the blood vessels of the brain and spinal cord be tight against one another, forming a blood-brain barrier?
It is the only barrier protecting the tissues in the brain from bacteria
Rhinocerebral Mucormycosis
Mucorales (order); Genus: Mucor; Fast growing fungi; Hypha growing around blood vessels; Sinusitis
Poliomyelitis
May become second human disease eradicated
Variant Creutzfeldt-Jakob Disease: Pathogenesis
Medical procedures can spread the disease; Prions may remain dormant for many years
Bacterial Diseases of the Nervous System
Meningitis, Leprosy, Botulism, Tetanus
Viral Diseases
Meningitis, Poliomyelitis, Rabies, Encephalitis
Meningococcal Meningitis: Pathogenesis
Meningococci adhere by pili, colonize upper respiratory tract, enter bloodstream; carried to meninges and spinal fluid; inflammatory response obstructs normal outflow of fluid; increased pressure caused by obstructed flow impairs brain function; damage to motor nerves produces paralysis; endotoxin release leads to shock
Viral Diseases of the Nervous System
More readily cross the blood brain barrier; Occurs more frequently than bacterial or fungal infections; Ineffective unless it enters cell, must has a host; Tend to be less severe; Infection of the blood is the root for most infections
Lepromatous Leprosy
More virulent form of the disease; Weak cell-mediated immune response
Viral Meningitis: Causative Agent
Most cases: small non-enveloped RNA enteroviruses of the picornavirus family; Coxsackie A, Coxsackie B, Echovirus
Leprosy: Treatment
Multiple antimicrobial medications; Treatment may be lifelong for some patients
Cryptococcal Meningoencephalitis
Order: Tremellales
Leprosy: Causative Agent
Mycobacterium leprae, an acid fast Gram positive rod that has not been grown in the absence of living cells; Only known bacterial pathogen of PNS
Leprosy: Virulence Factors
Mycolic acid in the cell wall is responsible for several characteristics: slow growth rate (3-20 years), protection from phagocytic lysis, growth within phagocytes, resistance to many antimicrobial drugs; Grows best in cooler regions of the body; Can live best inside infected cells for years; Cellular immune response eventually attacks infected cells: may destroy nerves and other tissues, lose sensations
Most Causative Agents of Bacterial Meningitis
Neisseria meningitidis, Streptococcus pneumoniae
Bacterial Meningitis: Causative Agents
Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, Listeria monocytogenes; Opportunistic members of normal microbiota can also cause meningitis
Peripheral Nervous System
Nerves, Ganglia
Viral Encephalitis: Treatment
No accepted treatment
Viral Meningitis: Treatment
No specific treatment exists
Tuberculoid Leprosy
Nonprogressive form of the disease; Strong cell-mediated immune response
Viral Encephalitis: Causative Agent
One of the five arboviruses, group of enveloped, single-stranded RNA viruses; LaCrosse, St. Louis, West Nile, Western Equine, or Eastern Equine
Glass Test
Place the bottom of a clear glass on rash, if the rash does not fade then it is a bacterial infection
Poliomyelitis: Causative Agents
Poliovirus 1, 2, 3 members of the picornavirus family
Cryptococcal Meningoencephalitis: Virulence Factors
Polysaccharide capsule resist phagocytosis
Botulism: Virulence Factor
Prevents the release of acetylcholine
Cranial Meninges
Primary spot for inflammation in the brain; Three connective tissue layers; Separate and support soft tissue of the brain; Enclose and protect blood vessels supplying the brain; Help contain and circulate cerebrospinal fluid
Foodborne Botulism
Progressive paralysis on both sides of the body; Slow recovery from growth of new nerve cell endings
Astrocyte Feet
Provide the blood brain barrier
Rabies: Causative Agent
Rabies virus, single-stranded RNA, Rhabdoviridae family; Has an unusual bullet shape
Viral Encephalitis: Pathogenesis
Replication of virus at the site of the mosquito bite, replication in lymph nodes, then viremia and invasion of brain tissue. Nerve cells in the brain destroyed. Process halted by neutralizing antibody
Ependymal Cell
Secrete cerebral spinal fluid
Leprosy: Signs and Symptoms
Skin lesions that lack sensation, deformed face, loss of finger or toes
Botulism: Prevention
Specific for the type, Foodborne is prevented by proper food handling and home-canning methods, also boiling home-canned foods for 10 minutes just prior to serving. Intestinal is difficult to prevent, but honey should not be fed to infants younger that 1 year of age. Wound is prevented through prompt and appropriate wound care
Viral Meningitis: Virulence Factors
Spread by fecal contamination of food, water, or hands; Spread by bloodstream (viremia) to other organs following ingestion; Cytolytic to intestinal cells
Poliomyelitis: Epidemiology
Spreads by the fecal-oral route, asymptomatic and non paralytic cases common; Polio currently exists in a few countries in Africa and Asia; Difficult to control in these regions because of several factors: political and religious tensions, poor sanitation, high population density; Risk for polio in well developed countries like U.S. because we are so sanitized and have not been exposed to the virus before so when it hits we are more prone to develop it; Exposure is key
Bacterial Meningitis: Signs and Symptoms
Sudden high fever, severe meningeal inflammation, and increased white blood cells in the CSF; Inflammation causes most signs and symptoms; Infection of the brain causes encephalitis: can result in behavioral changes, coma, and death; Can develop rapidly
Floppy Baby Syndrome
Symptoms are diagnostic; Four approaches to treatment: maintain open and functional airways, wash intestinal tract to remove Clostridium, administer botulism immune globulin, treat with antimicrobial drugs; Prevented by destroying endospores in contaminated food; Infants under 1 should not consume honey
Rabies: Epidemiology
Transmitted via bite or scratch from an infected animal, usually a bat. Inhalation is another possible mo Zoonotic disease
Cryptococcal Meningoencephalitis: Treatment
Treated with intravenous anti fungal drugs: Amphotericin B; No prevention
Bacterial Meningitis: Treatment
Treated with intravenous antimicrobial drugs; Vaccines available for S. pneumoniae, H. influenzae type b, and N. meningitidis; Administration of penicillin at birth reduces neonatal meningitis due to S. agalacitae; Individuals at risk for listeriosis should avoid high risk foods
Rabies: Diagnosis
Unique neurological symptoms
Viral Meningitis: Incubation Period
Usually 1 to 4 weeks
Botulism: Incubation Period
Usually 12 to 36 hours for food borne; Variable of unknown for other types
Rabies: Incubation Period
Usually 30 to 60 days; Sometimes many months or years
Viral Meningitis: Pathogenesis
Viremia from primary infection spreads to meninges. Fewer leukocytes enter cerebrospinal fluid than with bacterial infections, and many are monocytes rather than neutrophils; Damage to cells in the meninges triggers meningitis
Poliomyelitis: Pathogenesis
Virus infects the throat and intestine, circulates via the bloodstream, and enters some motor nerves of the brain or spinal cord; infected nerve cells lyse upon release of mature virus
Viral Encephalitis: Epidemiology
Viruses transmitted to humans from birds or rodents by mosquitoes
Variant Creutzfeldt-Jakob Disease: Epidemiology
vCJD can occur in young people