CNS Infections Flashcards
What are the most common etiológical agents responsible for CNS infections?
Bacteria and viruses
The diagnosis of a CNS infection is going to involve what?
A medical history, physical examination, CSF and blood analysis, gram stain, culture, PCR, serologic tests, Neuro imaging (MRI, CT)
Meningitis is identified by what?
An abnormal amount of white blood cells in the CSF
Infection of the brain meninges can be caused by a…
Bacteria or virus
What is the timeline of acute meningitis?
Hours to days
What are some microorganisms responsible for acute meningitis?
Strep pneumoniae, neisseria meningitidis, coxsackievirus and HSV-2
What is the timeline of subacute meningitis?
Days to weeks
What are the most common microorganisms responsible for subacute meningitis?
Mycobacterium tuberculosis, cryptococcus
Chronic meningitis is characterized by…?
At least 4 weeks of symptoms of inflammation in the CSF
Which organisms are responsible for asceptic meningitis?
Echovirus, cocksackie (A, B), HSV-2, HSV-1, VZV, EBV, CMV, HIV
Which organisms can cause meningitis in infants?
In infants less than 1 month old we have E. Coli, S agalactie, Listeria monocytogenes
In infants less than 1 month old the viruses responsible are enteroviruses, HSV, VZV, CMV
Parasites we have toxoplasma Gondi
Which bacteria are responsive for acute bacterial meningitis?
In individuals between 1 month and 50 years of age we have S pneumoniae , neisseria meningitidis and in people older than 50 years or age we have S pneumoniae, Listeria monocytogenes
Which microorganisms are responsive for chronic meningitis?
Mycobacterium tuberculosis, HIV, cryptococcus neoformans
What is the classical triad of meningitis?
Fever, headache, and nuchal rigidity
Which type of ascetic meningitis is not self limited in infants?
HSV-2
Acute meningitis is common in which population?
Adult population
L monocytogenes can be transmitted via the ingestion of what?
Contaminated dairy, hot dogs, fish
Strep pneumoniae can cause acute meningitis and be transmitted how?
Person to person respiratory droplets
How does the bacteria reach the meninges?
They start replicating in the primary site of infection and then they spread to the bloodstream and the lymphatic system until they come in to contact with the large venous sinuses where they can come in contact with the meninges
Acute bacterial meningitis can cause…
An increase in the white blood cells, release of toxic factors, necrosis of tissue, edema which leads to ICP, increased permeability of the blood brain barrier, low glucose levels, increased protein, increased amount of neutrophils, decreased blood flow which leads to ischemia
In M, tuberculosis there is…
Rupture of adjacent tubercle
Cryptococcus neoformans has a capsule plus what?
Melanin that doesn’t allow it to be easily phagocytized (provides protection)
What procedure do you do to establish a definitive diagnosis of meningitis?
Lumbar puncture
In order to perform a lumbar puncture what do we need first?
CT scan
When it comes to treating meningitis, the antibiotics are going to be delayed until what?
Blood and CSF samples are received
When it comes to treating aseptic meningitis, what is the treatment?
We give empirical antibiotics because we don’t know if the causative agent is a virus or a bacteria and once we have the CSF results and we know it’s a virus then we discontinue the antibiotics
When it comes to treating acute meningitis, what is the process?
We start by giving empiric antibiotics and once we know the exact etiological agent, we give a specific antibiotic. We also give the patient a vaccine
What is the treatment for infant meningitis?
We provide empirical antibiotics until all cultures are negative
Antibiotics:
- Ampicillin + cefotaxime or ceftriaxone
- Gentamicin
- Acyclovir
What medications are used to treat chronic meningitis?
Rifampin, pyrazinamide, ethambutol, amphotericin B, flucytosine, fluconazole
What is encephalitis?
Inflammation of the brain
What is a common causative agent of encephalitis?
Viruses
Encephalitis is distinguished by what?
Decreased mentation (abnormal state of consciousness with or without seizures) early in the course of the disease with minimal meninges signs
A person can acquire an encephalitis vis what modes of transmission?
Human to human contact ( example herpesvirus)
Zoonotic disease ( direct contact with animals)
Which virus that is transmitted via from animals to humans can induce encephalitis in humans?
arbovirus ( this virus is acquired via a mosquito bite and then spreads to the bloodstream)
What other viruses that are transmitted from animals to humans scan induce encephalitis in humans?
St Louis, California, Eastern, Western, West Nile, Venezuelan and the rabies virus which travels via the axons
What type of virus is the rhabdovirus?
Rabies virus
What are some characteristics of the rhabdovirus?
Single stranded, negative sense, non segmented, bullet-shaped, cytoplasmic replication
Which virus is most commonly responsible for encephalitis in humans?
HSV and it’s due to reactivation of the virus in the trigéminal ganglia
The west Nile virus is a…
Arbovirus
What percentage of people infected with the West Nile virus are going to be asymptomatic and what percentage is going to be flulike?
80% asymptomatic and 20% flulike
Which virus kills wild birds?
West Nile virus
Which type of virus is the most common cause of episodic encephalitis in the summer?
Arbovirus
The West Nile virus can be found in which places?
Africa, Europe, Asia, North America
Why animals tend to harbor the rabies virus?
Raccoons, skunks, bats, foxes, man goose
80% of people infected with the rabies virus tend to experience furious rabies, what are the symptoms?
Hyperactivity, agitation, hydrophobia, seizures
20% of patients infected with rabies tend to experience paralytic symptoms what are these symptoms?
Ascending paralysis without hyperactivity this is known as dumb rabies
What are some manifestations of rabies?
Fever, severe headache, altered mental status, meningeal irritation that manifests as a headache with nuchal rigidity, sensory or motor deficits, visual and auditory hallucinations, personality changes, confusion, sleepiness, coma
What are other manifestations of rabies?
Abrupt onset of hydrophobia, pharynx spasm, seizures that can lead to coma, diabetes insípidus or SIADH, arrhythmias, autonomic dysfunction, shallow quick respiration (these manifestation start to happen 10-240 days post exposure)
What is the order of the pathogen esos of the rabies virus?
- Replication outside the CNS
- Hematogenous/neural route CNS entry
- Neuronal damage due to immune response
- Neural cell entry
- Cell functioning disruption
- Perivascular congestión
- Hemorrhage
- Inflammatory response
Patients infected with rabies with start to develop what?
Negri bodies in the cerebellum/ hippocampus
Why is the inoculation site of the rabies virus?
Bite site
The rabies virus is going to be altering what?
Nicotinic acetylcholine receptors that are present in the nerve/muscle
How does the rabies virus travel throughout the body?
Via retrograde axoplasmic transport from the dorsal root ganglia to the spinal cord and then towards the brain
