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Microbiology > CNS Infections > Flashcards

CNS Infections Flashcards

1
Q

what are some general key differences in CSF between CNS bacterial and viral infections?

A

Glucose is low and neutrophils and protein are high in bacterial infections

lymphocytes and monocytes will be high in viral infections, protein in CSF is slightly elevated

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2
Q

what are the most common enteroviruses that cause encephalitis?

A

Coxsackie A and B viruses

Echo virus

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3
Q

describe the infectious course of enteroviruses - pathogenesis

A

Virus replication begins in the intestinal
mucosa and lymphoid tissue of the tonsils
and pharynx

spreads by viremia to
cells of the lymph nodes, spleen and liver -> replicates some more

cytolysis - burst out of cells they infect

immune response is IgA and IgG antibodies

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4
Q

what are the syndromes associated with coxsackie viruses?

A

Hand, foot and mouth disease

herpangina

pleurodynia

myocardinal and pericardial infections

aseptic meningitis

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5
Q

what are the ways the viruses get into the CNS?

A

Transported over in infected white blood cells - hematogenous dissemination?

invading peripheral nerves and traveling into the CNS - neuronal retrograde dissemination

infecting cells that form anatomical barriers

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6
Q

what’s the most common cause of encephalitis?

A

encephalitis - infection of the brain parenchyma

viral is more common than bacterial and fungal

often accompanied by viral meningitis

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7
Q

how does viral meningitis present?

A

inflammation of the subarachnoid membrane

fever, headache, nuchal rigidity and photophobia

CSF - lymphocytic pleocytosis

viral meningitis is typically a milder disease than bacterial or fungal meningitis

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8
Q

what classes of viruses are the most common causes of non-sporadic aseptic meningitis?

A

enteroviruses

arboviruses - responsible for epidemics

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9
Q

acid fast stain

A

TB

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10
Q

India Ink stain

A

cryptococcus neoformans

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11
Q

how is viral meningitis diagnosed?

A

evaluation of the CSF profile - lymphocytic pleocytosis, with normal protein, glucose

negative acid fast and india ink stains

negative cultures

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12
Q

what’s the primary diagnostic test for viral CNS infections?

A

PCR of the CSF

this is how you can tell the exact virus that’s infecting

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13
Q

describe the pathogenesis of enteroviruses

A

they spread by the oral-fecal route and divide in the GI tract.

They get out of the GI tract through peyer’s patches

viremia - virus travels in blood to lymph nodes. spleen and liver to replicate some more (symptoms)

viral replication damages the cell -> signs and symptoms of disease

IgA is the primary immune defense

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14
Q

hand, foot, and mouth disease

A

coxsackievirus virus syndrome - serotype A16

painful red blisters in the mouth, palms of hands and soles of feet.

self limited infection

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15
Q

herpangina

A

infection of the throat - rid ringed blisters and ulcers on tonsils and soft palate

fever, sore throat, pain on swallowing and vomiting

self-limited, coxsackie A

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16
Q

pleurodynia

A

bornholm disease - coxsackie B virus

acute illness with painful spasms in the muscles of the chest and upper abdomen, fever and pain ^

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17
Q

myocardinal and pericardinal infection

A

coxsackie B virus

sporadic occurance in all ages, life threatening in newborns

in newborns -> febrile illness and sudden heart failure

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18
Q

aseptic meningitis - coxsackieviruses

A

rarely encephalitis also occurs

can occur with petechiae/rash, full recovery in absence of encephalitis

can also be caused by echoviruses

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19
Q

arboviruses - how do they spread? In what ways can they present?

A

arthropod borne viral illness - spread by mosquitos and ticks, ofter get the infection themselves from a bird

often presents with few flu-like symptoms but can lead to dangerous encephalitis

can also present with hemorrhagic fevers which are life threatening

complications of encephalitis - coma, permanent brain damage and death

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20
Q

compare and contrast eastern and western equine encephalitis?

A

Both are spread by mosquito, with a bird intermediate, and infect horses as well as humans

eastern is rare and in the eastern US, 1/3 of people with clinical encephalitis die from this virus infection

western is in the west of the US and canada, patient presents with flu-like symptoms, anorexia, altered mental status and sign of meningeal irritation

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21
Q

st. louis encephalitis

A

SLE - leading cause of epidemic flavivirus encephalitis - most common mosquito transmitted disease in continental US

illness severilty ranges from febrile headache to meningoencephalitis

case fatality ratio of 5-15%

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22
Q

west nile virus

A

started in queens, 1999

infection can be asymptomatic or mild febrile disease but can also be severe and fatal

migratory birds play a role in disease spread

most common is desert-y areas of the US (SoCal., Az) and the midwest.

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23
Q

La Crosse Encephalitis

A

most cases are reported in children, 75 cases/yr

life cycle includes bird and small mammals (chipmunks and squirrels) Lives over winter in mosquito eggs - vector borne

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24
Q

Colorado tick fever

A

.

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25
Q

Colorado tick fever

A

most common tick borne viral disease in the US

animal reservoirs - small mammals

symptoms - headache, retro-orbital pain and muscle/joint aches

dog tick - prevalent in the Rocky Mountains

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26
Q

Japanese encephalitis

A

widespread in Asia, most important cause of arbovirus encephalitis worldwide

life cycle involves aquatic birds and mosquitos

there is a formalin-inactivated vaccine available

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27
Q

diagnosis of an arbovirus infection

A

using symptoms - headache, drowsiness and fever (less common are vomiting and stiff neck)

CSF lymphocytic pleocytosis, normal Glucose, normal or mildly elevated protein

definite diagnosis is based on IgM presence in CSF (this means the BBB has been broken)

also, PCR testing.

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28
Q

powassan encephalitis and deer tick virus

A

Ixodid ticks

powassan is rare but mostly found in the north east.

Deer tick virus is a relative of powassan - also rare cause of encephalitis but is becoming more common in Hudson Valley region of NY

serum/CSF detection using virus-specific monoclonal antibodies

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29
Q

HSV 1

A

Cowdry type A intranuclear inclusion bodies - from viral replication

infects epithelial cells at site of entry - mouth is most common - cold sores

visualized by Tzanck Smear using Giemsa stain

lives in the trigeminal ganglion where it stays latent, gets reactivated and replicated and reinfects.

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30
Q

HSV2

A

Cowdry type A intranuclear inclusion bodies - from viral replication

genital herpes - latency in sacral ganglia

also forms painful fluid filled cysts - result of viral replication

identified with a Tzanck smear via the giemsa stain

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31
Q

HSV Encephalitis

A

typically caused by HSV 1

upon reactivation the virus can spread to the lips (cold sores) but also to the brain or the meninges

most common cause of sporadic viral encephalitis

adults and pediatric

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32
Q

diagnosis of HSV Encephalitis

A

postive Tzanch smear - reveals the syncytia forming cells wit the cowdry type A intranuclear inclusions

CSF - lymphocytic pleocytosis, elevated protein but normal glucose, erythrocytes in CSF - disrupted/damaged brain tissue.

33
Q

Varicella-Zoster Virus

A

chicken pox in primary infection

subsequent infections causes shingles/herpes zoster

requires cell-mediated immunity for control of infection

herpes zoster infects dermatomes - forms a painful rash (postherpatic neuralgia)

more common in elderly, also causes viremia

34
Q

diagnosis of VZV infection

A

veiwing of syncytia and Cowdry type A intranuclear inclusions microscopically or Tzanck smear

35
Q

JC virus - infection in immunocompetent vs immunocompromised individuals? How is it diagnosed?

A

human polyoma virus

viral replication in host nucleus

virus enters vis the respiratory tract, spreads to kidneys, B cells and monocytes.

Latent infection people with competent immune systems.

reactivation in immunosuppresed - most commonly AIDS patients and organ transplantation

causes PML - progressive multifocal leukoencephalopathy: subacute demyelinating disease

diagnosed by symptoms, MRI/CT, PCR amplification of CSF

36
Q

Rabies virus

A

acute encephalitis in all warm-blooded hosts

reservoirs historically were dogs but now seen in raccoons, bats and rats - transmitted by salvia (bite) or through mucous membranes - eyes, nose, mouth

travels to CNS by way of sensory or motor neurons and forms cyoplasmic inclusion bodies known as Negri Bodies

37
Q

Lymphocytic choriomeningitis

A

arenavirus

flu-like disorder followed by meningitis

found in rodents: gray house mouse and hamster - they excrete the virus in urine, feces, semen and nasal secretions. Spread by contamination

38
Q

Prion Diseases -Transmissible Spongiform Encephalopathies

A

isoform of a normal protein that causes the protein to change shape and aggregate.

the altered protein is insoluble - amyloid-like plaques

neuronal degeneration

Creutzfeldt-Jakob disease is most common

rare are kuru, gerstmann-straussler syndrome and fatal familial insomnia

CJD is diagnosed by immunoassay

39
Q

treatment of HSV

A

acyclovir, valacyclovir,

penciclovir and famciclovir

40
Q

pathogenesis of the primary infection of VZV?

A

primary infection starts in the mucosa of the respiratory tract, replication happens in the lungs, disseminates through the bloodstream and causes the fluid-filled chicken pox vesicles. Travels on sensory nerves of the skin to lye latent in the DRG.

41
Q

Zostavax

A

vaccine for shingles

can only be given to those over 60 who had not had shingles before

similar to chicken pox vaccine

42
Q

Variant CJD

A

Variant creutzfeild jakob disease is thought to be caused by consumption of BSE infected meat/

prion protein can be detected in lymphoid tissue

occurs in young patients - psychiatric manifestations and ataxia

CJD is diagnosed by immunoassay

43
Q

whats the most common cause of bacterial meningitis in newborns?

A

s. agalactiae
l. monocytogenes
e. coli

44
Q

whats the most common cause of bacterial meningitis in the elderly?

A

L. monocytogenes

45
Q

whats the most common cause of bacterial meningitis in infants and toddlers? (up to 60mo)

A

S. pneumoniae

46
Q

presentation of acute bacterial meningitis

A

isolated clinical event.

fever, stiff neck, headache, global/focal CNS dysfunction, petechia on trunk and lower extremities.

causes elevated intracranial pressure because of blocked CSF flow due to pus accumulation

fatal without treatment - immediate Ab followed by CSF gram stain

47
Q

what antibiotics are good treatments for bacterial meningitis?

A

beta-lactams despite being polar

cefotaxime/ceftriaxone

dexamethasone - h. influenzae

chemoprophlyaxis for immediate contact

48
Q

which antibiotics are NOT for treating bacterial meningitis? WHY?

A

erthromycin

tetracycline

cefoxitin

1st generation cephalosporins

why? because these polar compounds cannot cross the BBB

49
Q

streptococcus pneumoniae - treatment, transmission and virulence factors

A

lives in throat and nasopharynx

spread by aerosol droplets

infection is purulent and associated with severe neurologic deficits and 21% mortality

often resistant to beta-lactams - treat with vancomycin

2 vaccines are available, the 13 valent is typically given to children and the 23 valent to elderly.

bacteria is encapsulated, contains IgA protease and pneumolysin

50
Q

neisseria meningitidis - treatment, transmission and virulence factors

A

colonizes healthy people, spread by aerosol droplets

grows on blood agar

encapsulated, IgA protease, B-lactamase

host immunity complement systems is very important

treatment with 3rd generation cephalosporins

vaccines available for A, C, Y and W135 serotypes but none for B

51
Q

listeria monocytogenes - treatment, transmission and virulence factors

A

most prevalent in immunocompromised patients with high mortality in elderly and neonates.

can be transmitted maternally through the placenta

treatment with ampicillin

salt and nitrite tolerant, can grow at low temperatures (4C)

vireulence factor - listerolysin O and actin polymerization

52
Q

streptococcus agalactiase - group B

A

group B strept

colonizes URT and GU tract

acquired by neonates during pregnancy or birth

no vaccine, treat with penicillin G

Gram stain of CSF and PCR for organism identification

increases risk for premature rupture of membranes. prolonged labor, preterm birth, disseminated maternal group B streptococcal disease and decreases maternal complement.

53
Q

chronic meningitis - bacterial causes

A

caused by latent TB activation

bacilli gets into CSF, settles in subarachnoid space where it causes an intense type 4 hypersensitivity reaction causing inflammation around CN’s leading to coma.

Acid fast stain for identification - only positive a small percentage of the time –> PCR

treated with several Abs

54
Q

Bacteria - brain abscess - what is it?

A

infection of the brain parenchyma can comes directly from paranasal sinuses, middle ear or mastoids.

can happen from dental surgery, trauma (penetration/surgery) or spread from blood during acute bacterial endocarditis

55
Q

Bacteria - brain abscess - what causes it?

A

staph aureus

anerobic and arobic microflora

group A or B strept

chronic - mycobacteria - TB

56
Q

bacteria - brain abscess - diagnosis and treatment

A

diagnosed by CT, MRI, aspiration of abscess

treated with antibiotics - Methicillin/vancomycin, ceftriaxone/cefotaxime &
metronidazole

not always effective, still 10-20% mortality with treatment, fatal without.

57
Q

chronic meningitis - clinical presentation

A

meningeal infection with pleocytosis lasting more than 4 weeks

Initial symptoms are headaches and fever.

Progression - seizures, change in mental status, confusion, hallucinations, development of focal neurologic deficits, hydrocephalus and increased ICP

Nuchal rigidity is either subtle or absent

58
Q

What type of microbial agents cause chronic meningitis?

A

fungal and parasitic microbes

infection and progression into meningitis in opportunistic - immunodeficit or suppressed peoples

59
Q

cryptococcus neoformans

A

fungi - india ink stain
(only fungus with capsule)

presents as subacute meningoencephalitis with progression to fever and hydrocephalus

Lab tech - Cryptococcal antigen latex agglutination

60
Q

What is the treatment for crypococcus neoformans caused chronic meningitis?

A

amphotericin B

flucytosine - nucleoside analogue that inhibits replication by inserting itself into the growing strand.

61
Q

histoplasma capsulatum

A

rare - endemic in Ohio River Valley

chronic meningitis

presents with fever, oral lesions, hepatosplenomegaly and hydrocephalus

lab diagnosis - seeing yeast cells inside macrophages, sometimes cultures, histoplasma polysaccharide antigen in urine/CSF/Blood

62
Q

Treatment of histoplasma capsulatem - chronic meningitis

A

amphotericin B

63
Q

Pseudallescheria - p. boydii

A

most common fungal agent of mycetoma

in immunocompromised - meningitis, meningoencephalitis and brain abscesses

organism acquired from polluted water, sewage and swamps

near drowning victim

resistant to amphotericin B

64
Q

taenia solium

A

parasitic
pork tapeworm - neurocysticercosis

chronic meningitis

presents with seizures, obstructive cysts, and space-occupying lesions

endemic in Mexico. South America and Asia

Lab Diag - CT and lymphocytic pleocytosis with eiosinophils (CNS?)

65
Q

treatment of chronic meningitis causes by taenia solium

A

albendazole

steroids

analgesics

anti-epileptic drugs

surgical resection of lesions and placement of ventricular shunts

66
Q

angiostrongylus cantonensus

A

parasitic chronic meningitis
rat lung worm - round worm

endemic in Asia and Pacific Islands

from ingestion of undercooked or raw shellfish or snails

can incubate for up to a year

presents with nausea, vomiting, neck stiffness and headaches that are global and severe. Rash with pruritus is also common (itchy)

diag - history and CSF - peripheral eosinophilia

no treatment

67
Q

Naegleria fowleri

A

Parasitic encephalitis

Protozoan - thermophile

Amebic meningoencephalitis - brain-eating disease

fatal

enters nose while swimming - freshwater in southern states, summer months, children and young adults are at highest risk

altered level of consciousness and lost sense of smell

lab diag - neutrophilic pleocytosis, motile trophozoites on wet mound of CSF, brain histopathology

68
Q

Balamuthia mandrillaris

A

parasitic encephalitis

protozoan in soil of Central America

entry - Cuts and wounds on skin or inhalation

Granulomatous Amebic Encephalitis - often misdiagnosed as TB
a) Subacute progressive disease with Space-
occupying lesions
b) Cranial nerve palsies
c) Hydrocephalus

lab DX - Serology and brain histopathology, Lymphocyte pleocytosis and depressed glucose, Real-time PCR of brain

poor prognosis, high mortality and slow progression (2yrs)

69
Q

Baylisascaris procyonis

A

Raccoon roundworm (helminthes)

caught by ingestion of eggs (contanmation) - eating dirt

Lab Dx - eosinophillic pleocytosis, peripheral eosinophillia and deep matter abnormalities, serology on CSF/Serum

mid-Atlantic, northeastern &
Midwestern states &
California

70
Q

Gnathostoma spp

A

round worm

Eating undercooked or raw freshwater
fish, eels, frogs, birds, & reptiles

tropical and subtropical areas - Thailand and Japan

Moves from skin to brain

DX - microscopic ID or larvae in tissue and ELISA

71
Q

Entamoeba histolytica

A

Predominantly a GI
disease

Diagnosis: serology &
PCR of brain abscess
aspirate or CSF

Treatment

Metronidazole or
tinidazole

Followed by
paromomycin or
iodoquinol

72
Q

Schistosoma japonicum aka Bilharzia

A

blood fluke - not found in the US

second highest impact worldwide after malaria - most devastating parasitic disease

lives in fresh water snails

Lab DX - Microscopic,, ELISA for anti-schistosomal Abs, granuloma formation in brain

73
Q

Paragonimus spp.

A

Lung fluke (flat worm)

Ingestion of raw or undercooked
crab or crayfish - rare in US but in Midwest (river raft in Missouri)

P. kellicotti - Symptoms similar to TB

Dx - microscopic examination of eggs and peipheral eosinophilia

74
Q

Parasites that can causes brain abscesses

A

Taenia solium

Entamoeba histolytica

Schistosoma japonicum

Paragonimus spp

75
Q

fungi that can cause brain abscesses

A

aspergilliuss spp - bone marrow and transplants

cryptococcus neoformans - T-cell immunity defects

Neutropenia pts - Aspergillis, Mucor and Candida

76
Q

symptoms of brain abscesses

A 
headache 
altered mental status 
focal neurologic findings 
fever 
nausea and vomiting 
seizure
77
Q

Labs of brain abscesses

A 
peripheral leukocytosis 
Low serum Na+ 
platelet counts may be high or low 
elevated erythrocyto sedimentation rate 
elecated CRP
78
Q

Schistosoma japonicum - brain abscess treatment

A

praziquantel

79
Q

Paragonimus spp. - brain abscess – Treatment

A

praziquantel

Microbiology (13 decks)

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