CSF Flashcards
A lumbar puncture procedure consists of:
a needle being inserted through a patient’s back
between two lower vertebrae and moved into the space surrounding the spinal cord.
the space
surrounding the spinal cord is filled with:
cerebrospinal fluid (CSF) that will drip from the needle
once properly inserted. Fluid will then be collected into sterile containers for laboratory testing
CSF collection from a ventricular shunt is accomplished through:
the placement of a catheter
behind the ear that will drain excess spinal fluid from the brain
A shunt is inserted into:
ventricles of the brain to relieve pressure caused by an accumulation of CSF
Catheter tubing is
placed to:
divert excess CSF either outside of the body for sterile collection or to other parts of the
body, such as the pleural or peritoneal cavities, to be absorbed by blood vessels
A catheter may be placed into a lateral ventricle that is attached to:
a reservoir implanted under the
scalp for external access to a shunt system
The reservoir is often used to
deliver drugs directly to
the CSF and CNS or to aspirate CSF for testing with a syringe in a minimally invasive manner
Haemophilus influenzae react and present in the following ways:
Catalase +
Oxidase +
X factor (hemin) +
V factor (NAD) +
Beta-hemolytic on sheep blood agar −
Lactose fermentation −
Mannose fermentation −
Gram stain: Haemophilus influenzae
GNRs
Growth requirements: Haemophilus influenzae
aerobic and facultative anaerobe, grow best on chocolate agar in 5–
10% CO2 at 35–37 °C
Colony morphology: Haemophilus influenzae
o Unencapsulated strains — small, smooth, and translucent on chocolate agar
o Encapsulated strains — larger, mucoid, with a mouse nest odor on chocolate agar.
Neisseria meningitidis react and present in the following ways
Catalase +
Oxidase +
Nitrate reduction −
Maltose fermentation +
Glucose fermentation +
Lactose fermentation −
Gram stain: Neisseria meningitidis
GND
Growth requirements: Neisseria meningitidis
aerobic and facultative anaerobe, grow best in a humid, 5–10% CO2
environment at 35–37 °C
Colony morphology: Neisseria meningitidis
a green hue may be present on agar underneath colonies
o Unencapsulated strains — medium, round, smooth, gray to white, moist on chocolate
and sheep blood agar
o Encapsulated strains — more mucoid appearing.
Escherichia coli react and present in the following ways:
Indole +
Citrate −
Hydrogen sulfide (H2S) −
Lysine decarboxylase (LDC) +
Lysine deaminase (LDA) −
Urease −
Motility +
Voges–Proskauer +
Triple sugar iron (TSI) agar A/A
Gas production +
Gram stain: E. coli
GNRs
growth requirements of e. coli
aerobic and facultative anaerobe, grow best at 37 °C
colony morphology: e coli
circular, convex colonies, dull gray, smooth on sheep blood agar, pink
to red, surrounded by dark-pink precipitate on MacConkey agar, and yellow on Hektoen and
xylose lysine deoxycholate agar (XLD) agars.
Listeria monocytogenes react and present in the following ways:
Catalase +
Motility at 20–25 °C +
Esculin +
Nitrate reduction −
Christie–Atkins–Munch–Petersen (CAMP) test +
Hippurate +
Glucose fermentation +
gram stain: Listeria monocytogenes
GNRs or CB
growth requirements; Listeria monocytogenes
aerobic and facultative anaerobe, grow best at 35–37 °C in ambient
air or 5–10% CO2
colony morphology; Listeria monocytogenes
white, translucent, smooth, moist, with a narrow zone of beta-
hemolysis on sheep blood agar
Corynebacterium species react and present in the following ways:
Catalase +
Motility −
Esculin −
Mycolic acids +
gram stain: Corynebacterium species
Gram-positive bacilli, slightly curved, with rounded ends — some species are
pleomorphic, presenting a Chinese letter formation appearance
Growth requirements: Corynebacterium species
aerobic and facultative anaerobe, grow best at 35–37 °C in ambient
air or 5–10% CO2
Colony morphology: Corynebacterium diphtheriae:
varying morphology from small, gray, and translucent
to medium, white, and opaque; black or gray colonies on cystine-tellurite blood agar
Colony morphology:
Less virulent Corynebacterium species:
small to medium, gray, white, or yellow,
nonhemolytic colonies
Propionibacterium species react and present in the following ways:
- Gram stain: Gram-positive bacilli, pleomorphic, diphtheroid-like, may be club shaped or in
palisade arrangements - Growth requirements: anaerobic, grow best at 35–37 °C for 48 hours
- Colony morphology: small white to gray on anaerobic blood agar. More mature colonies
will be larger and yellow colored
Correlating the appearance, microbiology, cell count, and chemistry testing of a CSF sample will
provide evidence for:
determining the presence of a meningitis infection, as well as differentiate the
causative agent.
The expected results of a normal CSF sample free of infection are as follows:
Appearance: clear and colorless
* Protein: 15–45 mg/dL
* Glucose: 60–70% plasma glucose levels
* Cell count: 0–5 WBC/µL
* Differential: 70% lymphocytes, 30% monocytes
Abnormalities in the color and clarity of a CSF sample can be indicative of the following
a traumatic
tap; current, recent, or previous subarachnoid hemorrhage; and infection.
Evidence of a traumatic
tap will show
blood in collection tubes, with a successive clearing in each tube, a clear supernatant
when spun, and clots from the presence of fibrinogen.
Samples will contain blood in every
collection tube during
a current subarachnoid hemorrhage, appear pale-pink to pale-orange in a
recent hemorrhage, and appear yellow in a past hemorrhage. A cloudy sample, maybe due to
increased WBCs, can be indicative of an infection
Bacterial infections can be detected and a presumptive causative organism can be
seen on a Gram
stain of CSF and correlated with the cell count and chemistry results.
Bacterial CSF lab values
CSF protein = greatly increased
CSF glucose= decreased
CSF WBC pop= Neutrophils
Lactate = increased
Viral CSF lab values
CSF protein = increased
CSF glucose = normal
CSF WBCs = lymphs
Fungal CSF lab values
CSF protein = increased
CSF glucose = normal - decreased
CSF WBCs = lymphs or monos
CSF lactate = increased
Direct detection methods for the evaluation and diagnosis of CSF infections includes
stains, rapid
latex antigen testing, and serological testing
Bacterial meningitis can be detected by the presence of
bacteria found on a Gram stain.
India ink and acid-fast stain preparations allow for
the direct
detection of Cryptococcus and tuberculosis pathogens, respectively.
Rapid latex antigen tests are
useful in the immediate detection of
classic meningitis causing bacteria such as S. pneumoniae, H.
influenzae, group B strep, E. coli, Neisseria meningitides, and Cryptococcus neoformans.
Latex beads
coated with
ensitized monoclonal IgG antibodies for each bacterium are added to a test card with a
CSF sample, mixed, and mechanically rotated for 5 minutes
Agglutination of the latex determines
the presence of bacterial antigens, thus indicating a bacterial infection
Serological methods are also
used in
determining syphilis infections of the CNS
The fluorescent treponemal antibody absorption
test
very sensitive but less specific in CSF samples than serum
Molecular methods aid in
detecting pathogens that do not grow on routine media or in patients who have already had
antibiotic treatments.
PCR testing is available for the detection and amplification of
nucleic acids in
the RNA or DNA of various CSF pathogens including bacteria, virus, fungi, and parasites.
COMMON MENINGITIS-CAUSING PATHOGENS
S. pneumoniae, H. influenzae, and N. meningitidis, E. coli and L. monocytogenes, Streptococcus agalactiae
Bacterial meningitis is caused by
opportunistic bacteria that enter the bloodstream, are carried
across the blood–brain barrier to the meninges, and spread throughout the spinal fluid
S. pneumoniae, H. influenzae, and N. meningitidis are
normal flora of the upper respiratory tract
and are spread from person to person by respiratory droplets.
The most susceptible population of meningitis are
children younger than 5 years of age, and pneumonia or bacteremia are commonly the initial
infection in a host prior to meningitis.
S. pneumoniae in meningitis
Pneumolysin: antiphagocytic capsular protein
o Several adhesion factors and immunogenic cell wall membrane
H. influenzae and N. meningitidis in meningitis
Encapsulated strains: resistant to phagocytosis and complement-mediated lysis
H. influenzae: in meningitis
B strain, most likely to cause meningitis
N. meningitidis: in meningitis
most common meningitis causing strains: A, B, C, Y, W.
E. coli and L. monocytogenes are transmitted via the: in meningitis
ingestion of contaminated food.
E. coli and L. monocytogenes, Streptococcus agalactiae: in meningitis
are common pathogens of neonatal meningitis due to transmission
from mother to baby at birth
S. agalactiae (group B strep): in meningitis
Polysaccharide capsule: prevents phagocytosis
Pore-forming toxins: promote entry into host cells and facilitate organism survival
E. coli: in meningitis
K1 strain: inhibits phagocytosis and resists bactericidal activity of serum antibodies
L. monocytogenes: in meningitis
Escape phagocytic vacuoles due to listeriolysin O, phospholipase A, and phospholipase
B.
COMMON PATHOGENS OF CSF SHUNT INFECTIONS
Coagulase-negative Staphylococcus
Corynebacterium
Propionibacterium
Contamination of the
shunt can occur
during surgery to implant the device or during the aftercare and maintenance of
the shunt.
Coagulase-negative Staphylococcus in CSF shunt infections
Encapsulated serotypes: resistant to phagocytosis
Several adhesion factors and biofilm producing the cell wall membrane
Corynebacterium in CSF shunt infections
Toxigenic strains are lysogenic due to exotoxin production
Propionibacterium in CSF shunt infections
Acquired resistance to the following antibiotic classes:
❖ Macrolides: erythromycin and azithromycin
❖ Lincosamides: clindamycin
❖ Tetracyclines: doxycycline and minocycline
