Ch.22 - MICROBIAL DISEASES OF THE NERVOUS SYSTEM PDF

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MICROBIAL DISEASES OF THE NERVOUS SYSTEM...

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Chapter 22 MICROBIAL DISEASES OF THE NERVOUS SYSTEM A. CAUSED BY BACTERIA 1. Bacterial meningitis:  Symptoms  Causes o Haemophilus influenzae o Neisseria meningitidis o Streptococcus pneumoniae  Diagnosis 2. Listeriosis 3. Tetanus 4. Botulism 5. Leprosy B. CAUSED BY VIRUS Poliomyelitis (Infantile paralysis)

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CHAPTER 23: MICROBIAL DISEASES OF THE NERVOUS SYSTEM The Human Nervous System Central Nervous System (CNS) o Brain and spinal cord Peripheral Nervous System (PNS) o All the nerves that branch off from the brain (cranial nerves) and the spinal cord (spina; nerves

The Meninges and CSF  Cranial and Spinal Meninges o Dura mater (outermost) o Arachnoid mater  Subarachnoid space: contains CSF  Is between the arachnoid mater and pia mater o Pia mater (innermost)  Cerebrospinal Fluid: o Bacteria can reproduce in it due to the low concentration of antibodies and phagocytes  Blood Brain Barrier o Selective for which materials can pass from the blood to the brain o Drugs cannot cross unless lipid-soluble o Has special transport channels for lipids and amino acids The Nervous System  Meningitis: inflammation of meninges due to massive arrival of white blood cells  Encephalitis: inflammation of the brain  Meningoencephalitis: inflammation of both the brain and meninges BACTERIAL MENINGITIS 

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Symptoms o Initial symptoms: Fever, Headache, Stiff neck o Followed by nausea and violent vomiting o May progress to convulsions and coma, eventually death  Convulsions are a clue that the CNS is involved o Sometimes takes as little as 24 hours to progress through to death Diagnosis o Stiff neck

Child diagnosis  Kernig’s sign – severe stiffness of the hamstring Must use a cerebrospinal fluid sample to make a diagnosis  Collected from the tail region of the spinal cord  Will show the infection because it is a fluid made fresh every day  If something is growing in it, it will be circulated  A gram stain of the CSF will be sufficient  Is the first step taken 1. Gram Stain of CSF  Will show the type of bacteria  Shows the best treatment option 2. Culture of CSF 3. Serology Tests  Based on antigen IG molecule vs AG  Need premade antibodies Treatment: 3rd generation cephalosporins o Why not suggest using chloramphenicol for all patients?  Possibility for Aplastic Anemia Prevention o 40% of the population are carriers  Asymptomatic  In the nasopharyngeal region o Avoid contact with other people’s saliva Cause: The meningitis causing bacteria all have a capsule o Haemophilus influenzae o Neisseria meningitidis o Streptococcus pneumoniae o o

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Spinal Tap (Lumbar Puncture)  Spinal needle is inserted, usually between the third and fourth lumbar vertebrae

Haemophilus influenzae Meningitis  Occurs in children (6 months to 4 years)  Gram negative

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6 strains  A through F o Strain B is most (95%) of the cases Capsule antigen Type B Prevented by HIB vaccine o Can be given at 6 weeks old o At 6 months old, have built unto the immunity  their body is capable of fighting off the infection o Up until 6 months, the child is dependent on the mother’s breast milk and can rely on their antibodies. When being weaned off and exposed to the bottle and other sources of food, they are now susceptible to the bacterium

Neisseria Meningitis  Also called meningococcal meningitis  Caused by N. meningitidis  10% of people are healthy nasopharyngeal carriers o Target is 0-5 y/o – most vulnerable o The group most affected is young adults (19-24 y/o) o Soldiers are also highly vulnerable o Prisoners are also susceptible  Sharing and close-contact makes you more susceptible to being affected by the disease  5 Big Strains o A, B, C, W135, Y o C is the most worrisome  Causes most of the cases in our region  Begins as a throat infection  Symptoms o High fever o Throbbing headache o Sore throat o Becomes septicemic easily  causing severe tissue damage  Can result in amputation  Petechiae  Indicators of severe septicemia  Purplish spots on the body o Can sometimes result in paralysis  Partial or full o Can result in deafness,  Partial or full  Harms the auditory nerve  Treatment o B-Lactam antibiotics  Penicillin  Third generation Cephalosporins  RAPID DIAGNOSIS IS IMPORTANT  24-hour window to lose the patient  Vaccination recommended for students

Streptococcus pneumoniae Meningitis  Also called pneumococcal meningitis  Caused by S. pneumoniae  80-83 strains  All have capsules  70% of people are healthy nasopharyngeal carriers  Entry points o Head or neck trauma o Head or neck surgery o Otitis media and sinus infections can be entry points  Most common in children (1 month to 4 years)  Mortality: 30% in children, 80% in elderly o Children and elderly are most susceptible  Prevented by vaccination o Pneumococcal vaccine for prevention – Too many strains to protect from all of them Listeriosis  Caused by Listeria monocytogenes  Usually foodborne o Only one that enters through food  Is a psychrotroph  Can be transmitted to a fetus  Most affected are the immunosuppressed o Pregnant  Causes very ill new born with very little chance of survival  60-65% mortality rate for babies one year after birth  Surviving babies may have mental defects  Stillborn babies  Miscarriages o Surgery patients o Cancer patients  Reproduced in phagocytes

Escherichia coli  Newborns  Contracted from the mother (Mother is unharmed)  The passing of the baby through the birth canal is when they are exposed to it Tetanus  Caused by Clostridium tetani  Grows in deep wounds  Produces exotoxins  Tetanospasmin released blocks relaxation pathway in muscles o Inhibits the release of GABA  GABA blocks the relaxation cycle  Symptoms o Period of general irritability o Stiffness in the neck (Early part of detection) o Lockjaw o Back spasms o Heart spasms  death  Prevention by vaccination with tetanus toxoid (DTP) and booster (Dt) Botulism  Caused by Clostridium botulinum  Intoxication comes from ingesting botulinal toxin  Causes paralysis  Produces exotoxins – Botulinal toxin o 4 strains (A, B, E, F) that attack humans  Type A is the most virulent o Type A toxin: 60–70% fatality o Type B toxin: 25% fatality o Type E toxin: 25% fatality  Botulinal toxin Inhibits acetylcholine release o Blocks excitation at the NMJ o Blocks release of neurotransmitter, causing flaccid paralysis  Lethal form of food poisoning o Often contracted from canned foods o Through soil contamination  E.g., mushrooms, beets  Symptoms

Dry mouth Abdominal distress Diarrhea (in adults)/constipation (in children) Blurred/double vision  First sign it is attacking the NMJ Shut down of the lungs and heart  paralysis  death Prevention o o o o

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Leprosy  Also called Hansen’s disease  Caused by Mycobacterium leprae  Acid-fast rod  Growth  Transmission requires prolonged contact with an infected person  Two forms o Tuberculoid (neural) form: Loss of sensation in skin areas o Lepromatous (progressive) form: Disfiguring nodules over body

Poliomyelitis (Polio)  Also known as infantile paralysis  Caused by a virus: Poliovirus  Transmitted by ingestion  Enters though the fecal-oral route o Lives in fecal matter and enters through the mouth o GI entry point  Initial symptoms o Nausea and Sore throat  Latch onto the pharyngeal region and small intestine  Multiply in the throat and small intestine  After multiplication, make their way to the blood  Viremia may occur o Bacteria in the blood = viremia o Viremia can take two forms  Transient viremia  Body’s immune system can take care of it  Does not progress beyond blood infection  No clinical symptoms  Persistent Viremia  Persists in the blood  Moves into the CNS

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Begins to grow in the motor neurons  causing death of the motor neurons  Death of Motor Neurons = paralysis Destruction of motor cells and paralysis occurs in...