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