Infectious Agents Flashcards by Jimmy Urness

What are common symptoms of meningitis?

HA
Neck Stiffness
Fever
Photophobia

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What are the most common causes of viral meningitis?

Coxsackie Virus
Echovirus
Arbovirus (Mosquito)

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If a healthy 34 year old male presents to the ED with a headache with a fever and CT reveals a well-circumscribed lesion, what might be the infectious agent responsible?

- Staph Aureas

- - Strep

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What are characteristic findings of brain abscesses to have a confirmatory diagnosis?

- Well-circumscribed lesion with central necrosis
- Fibrotic Wall of collagen
- Numerous PMNs surrounding
- “Ring Enhancement Lesion” on imaging

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What might be the CSF findings of TB-associated meningoencephalitis?

- Elevated Lymphocytes

- - Low Blood Glucose

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What are unique characteristics of TB-meningoencephalitis?

- Enhancement of the base of brain on MRI + vasculitis
- Tuberculoma - mass lesion w/ central caseous necrosis with Epithelial Histiocytes / Giant Cells
- Pott’s Disease - granulomatous process of vertebral bodies leading to cord compression

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What chronic infection is manifests with general paresis, meningovascular meningitis, and tabes dorsalis?

Treponema Pallidum

- gradual cognitive impairment
- chronic multifocal arteritis–infarctions-thickening of vessels walls until occulsion
-Lightning pains, loss of positional-vibrational senses

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If on an after death autopsy you unconver perivascular lymphocytic infiltrates, microglial nodules, and neuronophagia; what might have been a pathologic process occurring at the time of death?

Viral Encephalitis

–Those symptoms are consistant with general viral encephalitis

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A 27 year old female presents to the emergency department with abnormal behavior according to friends and erratic moods complaining of a headache several days ago. What might be found on MRI scan?

HSV1 Most Likely

Focal abnormalities of the Temporal Lobes
Hemorrhagic inflammatory necrosis / swelling

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If a biopsy what taken of an individual thought to have Herpes Simplex encephalitis what might they find?

Intranuclear inclusion bodies

- Cowdry Type A Cells

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Contrast the patient populations who acquire HSV1 and HSV2 encephalitis?

HSV1 – General Population

HSV2 – Neonates who acquire HSV2 from active infection in the mother during birth.

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How is Arbovirus acquired and when should you be suspicious of Arbovirus?

Mosquitos – Season, most common during the summer.

Epidemic Encephalitis – when several people in the community contract it.

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What virus most common affects Microglial cells?

HIV

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What are the symptoms associated with chronic HIV infection?

Infect Microglial Cells

- develop HIV Encephalitis over time (years)
- Cognitive/Behavioral deterioration
- Ataxia / Tremor

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What histologic findings is consistent with HIV encephalitis?

Microglia Nodule with Multinucleated microglial cells

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What conditional affects the oligodendrocytes?

Progressive Multifocal Leukoencepholopahty

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What is responsible for Progressive Multifocal Leukoencephalopathy?

Reactivation of JC Virus

– Immunocompromised individuals

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How does Progressive Multifocal Leukoencephalopathy affect the brain?

- Affects white matter
- numerous irregular small focal areas of demyelination of the white matter
- oligodendrocyte inclusions

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What might you find with Apergillus / Mucor encephalitis?

– Vasculitis causing small localized hemorrhage infarcts

if Aspergillus – vessels infiltrated with hyphae

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Where does Cryptococcosus come from and how does it end up infecting the brain?

Immunocompromised individuals

- Bird Poop
- Infects the lungs first, then hemagenously spreads to the brain cauing encephalitis/abscesses

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What are histologic findings with Cryptococcus?

- Thickening of the Meninges from chronic inflammation
- Intraparenchymal cysts – “Soap Bubbles”
- Yeast form of fungi

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If you become infected with Toxoplasma what might the pathologic findings be?

Very small areas of necrosis throughout the brain

- Organisms free in tissue in pseudocysts

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What are the common causes of Epidural / Subdural empyemas?

Hematagenous spread from ENT infection

- Strep
- Staph

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What is the common clinical presentation of Prion Disease?

Rapid progression of dementia, ataxia, myoclonic jerking
– EEG = triphasic waves 1-2s
– MRI = increased signal in basal ganglia
Symptom onset progression in months, death within a year.

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What are the most common causes of Prion Disease?

- Idiopathic -- Creutzfeld-Jakob Disease (50%) - Inherited (15%) - Acquired from Surgery - Eating Cow w/ Mad Cow

What is the mechanism of action of the abnormal proteins in Prion Disease?

- Abnormal PrPsc infiltrates the body and is able to interact with normal PrPc proteins changing them into abnormal versions - PrPsc do not degrade normally and aggregate in the brain causing the symptoms

What is the most common cause of meningitis?

Strep Pneumoniae

What is the most common types of meningitis in children less than 1 year old?

Neisseria Meningitidis | Group B Strep

What is commonly found in adults over the age of 50 and/or immunocompromised?

Listeria Meningitis

What types of bacteria can cause meningitis after surgery or neurosurgery?

Skin Bacteria - Strep Agalactiae - Staph Epidermis

What might be the causative agent in an individual with meningitis symptoms progressive over several weeks?

Cryptococcus -- immune compromised

What causative agent might be at fault for development of meningitis during the summer months?

- - Enterovirus | - - Arbovirus / Borrelia Burgdorfi / Ricketti -- Mosquitos

What is the most common etiology of meningitis of a 2 year old who lives in a closed community?

-- Haemophilus Influenza

What are the differences in CSF findings when evaluating for meningitis?

Bacteria -- Elevated PMNs, Low Glucose Viral -- Elevated Lymphocytes, Normal Glucose Fungi -- Elevated Lymphocytes, Low Glucose

What should be started as empiric therapy for a 57 year old male with negative gram staining CSF?

- Ceftriaxone - Vancomycin - Corticostertiods - Ampicillin -- only if gram negative and 50+ (Listeria)

What are the two most common causes of meningitis?

- Strep Pneumoniae - everyone | - Neisseria Meningitis -- under 1 and 16-21 year olds

What is the most common means of acquiring meningitis from strep pneumoniae?

-- Pneumonia first, then has hemagenous spread into the blood brain barrier -- Meningitis

What serotype is not protected with the Neisseria conjugate vaccine?

Serotype B -- due to reactivate to human self-antigens

Who are most suspectible to Haemophilus Influenza meningitis?

Between the ages of 3 months and 3 years

What is the the capsule made from of the most virulent strain of Haemophilus?

Ribose / Ribitol -- Type B

Why is an infant not suspectible to Haemophilus immediately after birth?

-- due to maternal antibodies circulating for up to 3 months

What are the characteristics of Haemophilus?

- gram negative | - small coccibacilli

What does the Haemophilus vaccine consist of and how does it prevent infection?

- PRP-D + Diptheria (Conjugate Vaccine) | - Induces a T-cell dependent response producing Memory T-cells

If a CSF sample gram stains positive with diplococci, what might be the organism?

Strep Pneumoniae

What are the virulence factors of Neisseria?

- Lipooligosacchride - Polysacchride Capsule - Fimbriae - attachment

How does Neisseria go about causing meningitis?

-- Fimbriae attaches in the Nasopharynx, then Lipooligosacchride induce immune response and it can slip into the blood-brain barrier

Who are the patient populations most susceptible to Neisseria infections?

- Under 1 year old - 16 - 21 years old attending college-close quarters - Asplenic individuals

What patient population is recommended to get the MCV4 vaccine?

MCV4 --- Neisseria Conjugate Vaccine | -- Anyone under the age of 55

How is the MPSV4 Vaccine different from the MCV4?

MCV4 - Conjugated Vaccine MPSV4 -- Polysacchride Non-conjucated -- Used for 55+ individuals expanded coverage of strains of Neisseria

How is the Neisseria presentation unique in meningitis?

- Very Rapid Progression of symptoms and demise after infiltrating the CNS

What extra precaution should be taken when dealing with Neissera?

-- Any contact with the patient should receive prophylaxis Antibiotics

What are the characteristics of Strep Pneumoniae?

- Gram Positive diplococci | - Alpha-hemalytic

What other regions does Strep Pneumoniae infect besides the CNS?

- Otitis Media - Pneumonia - Pharyngitis - Sinusitis

When might you give the PPSV23 vaccine to a patient?

After they turn 65 for an expanded spectrum of protection from strep pneumoniae -- polysacchride vaccine

What is the PCV13 vaccine used for?

Conjugate Vaccine against Strep Pneumoniae | -- Given to Everyone

What patient population might Strep agalactiae meningitis be found in?

- - Neonates / Preterm Infants | - - Bacteria resides in the mothers vagina and can infect the baby as being delivered.

You can prevent Strep Group B from infecting a neonate on delivery?

- - Prophylaxis can be given to the mother if she previously had a child infected - - Penicillin

Is there a vaccine for Strep Agalactiae? What is the treatment?

No there is no vaccine. | -- Treat with Penicillin

What are the characteristics of Rabies virus?

- Rhabdovirus / Rod Bullet shaped - (-)ssRNA - Can bind ACh receptors throughout the body getting into the PNS

When the rabies virus is replicating, does it cause the host cell to die?

- No.

How does the rabies virus go about infecting the CNS?

- enters through an abrasion / bite in the skin / transplant - variable latent period - enters PNS carried into the CNS - once into CNS rapid replication, then spread distally

What are the tissues most common associated with rabies infection?

- Eyes - Salivary Glands - Hair Follicles

What site of infection would cause a more rapid progression of rabies disease? - - Ankle Bite - - Abdominal Scratch

Abdominal Scratch with rabies infected animal, closer to the CNS. -- further away the longer it takes

What are the initial symptoms of a rabies infection?

- Nervousness - Anxiety - HA / Fever/ Nausea

What are the end-stage symptoms of Rabies?

- Crazed Behavior / Aggressive - Hydrophobia - Flaccid Paralysis

How can you diagnose an individual with Rabies?

- - Most commonly focal neurologic symptom with a history with possible exposure - - Sometimes: Negri Bodies / Direct Flourescence Antibodies

What is the most common exposure to Rabies in North America?

- Bats / Rabid Wild Animals

What is the post-exposure prophylaxis when exposed to Rabies? Is it time sensitive?

- - Give Passive Immunization HRIG/ERIG (immunoglobin) in order to prevent the spread of the virus from its localized infection point - - Begin Vaccine at the same time x4 doses - - Somewhat time sensitive, but sooner rather than later