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22-Study Guide MBIO
Chapter 22: Microbial Diseases of the Nervous System
| Term | Definition |
|---|---|
| Central Nervous System (CNS) consists of | brain (protected by skull) and spinal cord (protected by backbone) |
| Peripheral Nervous System (PNS) consists of | nerves that branch from CNS |
| Meninges that cover the CNS | dura mater, arachnoid mater, and pia mater |
| CSF circulates | in the subarachnoid space: between arachnoid and pia mater |
| purpose of blood-brain barrier | prevents many substances, including antibiotics, from entering the brain |
| How do microorganisms enter the CNS? | trauma, along peripheral nerves, bloodstream, lymphatic system, |
| meningitis | infection of the meninges |
| encephalitis | infection of the brain |
| Three major causes of bacterial meningitis | Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis |
| H. influenzae | part of normal throat microbiota, requires blood factors for growth |
| H. influenzae serotypes | based on capsules |
| H. influenzae type b | most common cause of meningitis in children <4 |
| H. influenzae type b vaccine | conjugated vaccine directed against the capsular polysaccharide antigen |
| N. meningitidis causes | meningococcal meningitis |
| Location and transmission of N. meningitidis | located in throats of healthy carriers and transmitted by droplet aerosols or direct contact with secretions |
| How do meningococci gain access to meninges? | through the blood stream, bacteria is found in leukocytes in CSF |
| Meningitis vaccine | purified capsular polysaccharide vaccine against serotypes A, C, Y and W-135 |
| Where can S. pneumoniae be found? | nasopharynx |
| S. pneumoniae meningitis | young children are most susceptible, untreated it has a high mortality rate, conjugated vaccine available |
| Listeria monocytogenes causes | meningitis in newborns, immunosuppressed, pregnant, and cancer patients/ spontaneous abortion, stillbirth when it crosses placenta |
| L. monocytogenes acquired by | ingestion of contaminated food, may be asymptomatic in healthy adults |
| Tetanus caused by | exotoxin produced by Clostridium tetani |
| C. tetani produces | the neurotoxin, tetanospasmin |
| Symptoms of tetanus | caused by tetanospasmin; spasms, contraction of muscles controlling the jaw, and death from spasms of respiratory muscles |
| Tetanus immunity | DTaP vaccine/ post injury: immunized pt receives booster of toxoid, unimmunized receives tetanus immune globulin |
| Tetanus infection treatment | debridement and antibiotics |
| Botulism caused by | exotoxin produced by C. botulinum growing in foods (serological type A botulinum toxin is the most virulent) |
| Botulinum toxin | neurotoxin that inhibits the transmission of nerve impulses |
| symptoms of botulism | blurred vision after 1-2 days, progressive flaccid paralysis for 1-10 days, possible death from respiratory and cardiac failure |
| C. botulinum growth inhibited by | acidic foods, aerobic environments, addition of nitrates into foods |
| Botulinum toxin can be destroyed by | boiling- 100C for 5 minutes |
| Infant botulism | results from growth of C. botulinum in an infant's intestines |
| Wound botulism | occurs when C. botulinum grows in anaerobic wounds |
| Botulism diagnosis | mice protected with antitoxin are inoculated with toxin from patient or foods |
| Leprosy/ Hansen's disease | caused by Mycobacterium leprae or M. lepromatosis |
| M. leprae and M. lepromatosis | cannot be cultured on artificial media, only on armadillos and mouse footpads |
| Tuberculoid form of leprosy | characterized by loss of sensation in the skin surrounded by nodules |
| Lepromatous form of leprosy | disseminated nodules and tissue necrosis |
| untreated Leprosy | cause death of secondary bacterial complications; tuberculosis |
| Leprosy diagnosis | observation of acid-fast rods in a skin biopsy |
| Poliomyelitis symptoms | sore throat, nausea, and occasionally paralysis |
| Poliovirus is transmitted by | ingestion of water contaminated with feces |
| Poliovirus invades | lymph nodes of the neck and small intestine, followed by viremia and possibly spinal cord involvement |
| Poliovirus diagnosis | based on isolation of the virus from feces and throat secretions |
| The Salk vaccine | inactivated polio vaccine; injection of formalin-inactivated viruses and boosters every few years |
| The Sabin vaccine | oral polio vaccine; contains three live attenuated strains of poliovirus and is administered orally |
| Rabies virus (Lyssavirus) | causes an acute, fatal, encephalitis |
| Rabies transmission | contracted through the bite of a rabid animal or invasion through skin, virus multiplies in skeletal muscles and connective tissue |
| Encephalitis (from rabies) | occurs when the virus moves along peripheral nerves to the CNS |
| Symptoms of Rabies | spasms of the mouth and throat muscles, extensive brain and spinal cord damage, and death |
| Diagnosis of Rabies | DFA tests of saliva, serum, CSF or brain smears |
| Reservoirs for Rabies | skunks, bats, foxes, racoons, domestic cattle, domestic dogs, domestic cats. |
| Post-exposure treatment for Rabies | administration of human rabies immune globulin (RIG) and intramuscular injections of vaccine |
| Arboviral encephalitis symptoms | chills, headache, fever, coma |
| Arboviral encephalitis transmission | arboviruses through mosquitoes |
| Zika virus | arbovirus often mild in adults but can cause CNS birth defects if it infects a fetus |
| Control of arboviral infections | control of the mosquito vector |
| Cryptococcus spp. | encapsulated yeastlike fungi that cause cryptococcosis |
| Cryptococcosis transmission | inhaling dried infected pigeon or chicken droppings |
| Cryptococcosis | begins as a lung infection, spreads to brain and meninges, immunosuppressed are most susceptible |
| Cryptococcosis diagnosis | based on latex agglutination tests for cryptococcal antigens in serum or CSF |
| African Trypanosomiasis caused by | protozoa Trypanosoma brucei gambiense and T.b. rhodesiense |
| African Trypanosomiasis transmitted by | bite of the tsetse fly |
| African Trypanosomiasis affects | nervous system of host causing lethargy and coma (commonly called sleeping sickness) |
| Why is there no vaccine for African Trypanosomiasis? | because of the protozoan's ability to change its surface antigens |
| Amebic Meningoencephalitis caused by | protozoan Naegleria fowleri |
| Granulomatous amebic encephalitis caused by | Acanthamoeba spp. and Balamuthia mandrillaris |
| Prions | self-replicating proteins with no detectable nucleic acids |
| Prions cause | diseases of the CNS that progress slowly and cause spongiform degeneration |
| Transmissible spongiform encephalopathies cause by | prions that are transferable from one animal to another |
| Creutzfeldt-Jakob disease and kuru | human diseases similar to scrapie, transmitted between humans |
| Causes of these diseases are still unknown | flaccid myelitis, Bell's palsy, and chronic fatigue syndrome |
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