Central Nervous System Infections. INTRODUCTION. * Central nervous system infections are usually: 1- Blood-borne invasion ; most common (e.g. polioviruses or Neisseria meningitidis) 2- Invasion via peripheral nerves ; less common
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* Central nervous system infections are usually:
1- Blood-borne invasion; most common
(e.g. polioviruses or Neisseria meningitidis)
2- Invasion via peripheral nerves; less common
(e.g. herpes simplex, varicella-zoster, rabies)
1- Blood-borne invasion takes place across:
- blood-brain barrier (encephalitis)
- blood-cerebrospinal fluid (CSF) barrier (meningitis).
* Microbes can traverse these barriers by:
- Infecting the cells that comprise barrier.
2-Invasion via peripheral nerves:
* Herpes simplex virus (HSV) and varicella-zoster virus (VZV) present in skin or mucosal lesions travel up axons to reach the dorsal root ganglia.
* Rabies virus, introduced into muscle tissues by:
- bite of a rabid animal.
- It enters peripheral nerves and travels to CNS,
to reach the neurons.
* In CNS; viruses infect neural cells, sometimes showing a marked preference.
* Polio and rabies viruses invade neurons. CJD virus invades oligodendrocytes.
* Spread of infection is direct from cell to cell along established nervous pathways.
* Bacteria and protozoa induce brain abscesses.
*Meningitis is one of the most terrifying disease.
* It can be fatal in hours.
* Early symptoms resemble
* A general name for inflammation of:
Sheaths that cover brain and spinal cord
b) Cerebrospinal fluid:
Fluid that circulates in the spaces
in and around brain and spinal cord
* Meningitis can be caused by:
infectious or non-infectious agents
* Infectious agents include:
bacteria, viruses, fungi, protozoa
Most common causes of meningitis are:
a)Bacterial infections (Septic meningitis)
may result in death or brain damage.
b)Viral infections (Aseptic meningitis)
usually resolve without treatment.
Adults and children
Neonates and the elderly often present atypically
*Meningococcus: The causative organism of epidemic cerebrospinal meningitis.
* Aerobic gram-negative diplococci.
*13 serogroups based on polysaccharide capsule.
*Most invasive disease caused by:
serogroups A, B, C, Y, and W-135.
* Organism colonizes membranes of nasopharynx.
* Organism may reach blood stream producing meningococcemia, the symptoms may be like upper respiratory tract infection.
* Meningococcemia may occur with or without meningitis.
* Meningitis is the most common complication of meningococcemia.
* Transmission: respiratory droplets
* Incubation period: 3-4 days
* Clinical Features
- Stiff neck
- Hypotension, and rash
- Cerebrospinal fluid (CSF)
. Fluid usually collected from
. A sterile needle is
inserted between 4th and 5th
lumbar vertebrae and the CSF
is allowed to drip into a dry
Appearance Cells (WBC’s) Protein Glucose
Normal CSFClear colorless Below 5x106/l 15-40mg% 45-72mg%
Pyogenic Purulent/cloudy usually many High very low Bacterial pus cells
Viral Clear/slightly Raised Normal or usually Meningitis turbid lymphocytes increased
Tuberculosis Clear/slightly Raised High reduced Meningitis turbid lymphocytes
on chocolate agar in 5-10% CO2
Gm –ve diplococci intracellular in pus
* Penicillin G is drug of choice for patients
*Chloramphenicol and cephalosporins for:
- persons allergic to penicillin or
- strain is resistant to penicillin
* Chemoprophylaxis for contacts:
- Rifampicin, orally twice daily for 2 days
- Ciprofloxacin as a single oral dose
- A polyvalent vaccine from the capsular polysaccharide of groups A, C, Y and
- The vaccine does not include group B polysaccharide.
Most patients recover completely on their own
* Tetanus (Greek Word) Tetanos means to contract
* Tetanus is an acute, often fatal, disease caused by:
An exotoxinproduced by Clostridium tetani
*Toxins are produced with growth of bacteria.
* Tetanospasmin toxin:
- Estimated human lethal dose (2.5 ng/kg).
* Clostridium tetani:
- Anaerobic gram-positive bacilli
- Spore-forming bacteria
* It is characterized by:
. Generalized rigidity
. Convulsive spasms of skeletal muscles
. Muscle stiffness of jaw and neck (lockjaw)
* It is prevented by immunization with tetanustoxoid
* Spores of Cl. tetani are found in soils and animal feces.
* Spores are very resistant to: - heat
* Spores can survive for a long time in environment(months or years)
Transmissionby: contaminated wounds
- Surgical wounds
- Deep puncture wounds
- Crush wounds
- Dental infection
- Animal bites
- Delivery or abortion
At wound, blood supply to tissues decreases.
Cl. tetani spores germinate into active vegetative cell that grows and produces
* Tetanospasmin is a lethal neurotoxin.
* It Induces spastic paralysis by:
inhibiting release of inhibitory neurotransmitters
which lead to uncontrolled muscle contractions
* Lock jaw:
Convulsive muscle contractions of the jaw
Extension of lower extremities, flexion of upper extremities and arching of the back.
* Neck rigidity
Heart or respiratory failure
* Tetanus is suspected upon exposure to a bite or a wound.
* Diagnosis depends on:
Clinical findings and history.
* Because Cl. tetani exhibits such sensitivity to O2
it is very difficult to recover and/or grow from clinical
* Antitoxin is administered
* Muscle relaxants
* Supportive therapy (ventilator)
* Cleansing of the wound
* A highly effective vaccine is available.
* Tetanus immunity is achieved using:
- A formalized tetanus toxoid.
- Toxoid is administered as part of DTP vaccine
* Boosters every 10 yrs.
- 7 types (A-G)
- Types A, B, E are the most common
* Cl. botulinum spores widespread in:
- contaminated vegetables
- meat and fish
* Canned or preserved foods
(without adequate sterilization)
- Spores survive and germinate in
- Formation of toxin
- Blurry vision, ptosis, dysphasia
*Diagnosis of botulism is mainly clinical
* Laboratory confirmation
* Supportive care:
- Mechanical ventilation
* Passive immunization (antitoxin)
- Trivalent antitoxin (Types A, B and E toxins).
- Serum sickness (9 %)
- Anaphylaxis (2 %)