Exam VI - Blood, Brain, and Urine Flashcards Preview

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Rickettsia: General Information

obligate intracellular organism (also erhlichia and anaplasma
gram - coccobacilli (rods)
vector: arthropods
main symptoms: fever, rash, and headache
visualization: Giemsa stain aka blood smear
Dx: serology

Rickettsia species: rickettsii, akari, prowazekii, typhi, and orienta tsutsugamushi


Rickettsia rickettsii

Rocky Mountain Spotted Fever
Vector: Dog and Wood tick
Reservoir: wild rodents
Geography: name is misleading more common in southeastern U.S. due to presence of ticks
Season: April to September

Incubation: 1 week
transmission: tick to tick is transovarial (passed on to subsequent generations), then transfers to humans
symptoms: centripetal rash that starts on extremities then spreads to the torso with petechial spots from blood vessel damage, headache, fever, conjuctival redness, and myalgia
Dx: microimmunofluorescence (MIF) that detects Ab
high mortality rate: 10-25%


Rickettsia akari

Rickettsial pox (like chicken pox)
vector: mites
reservoir: mice
disease: mild and self limiting (immune response cures)
sign + symptoms: papules that progress to water filled vesicles
9-14 days later, high fever, headache, chills, photophobic, and increased amount of vesicles that become crusty


Rickettsia prowazekii

Epidemic typhus
vector: body lice
reservoir: humans (horizontal transmission)
conditions: war, army, refugee camps, poverty, natural disaster, etc.
signs + symptoms: 8 days- headache, fever, and chills, then 4-5 days later patient develops small pink flat macules on trunk that spread outwards (centrifugal rash), but NO rash on soles, palms, and face


Rickettsia typhi

Endemic typhus aka murine typhus (occurs all the time)
Vector: flea
Reservoir: rodents
Geography: worldwide in warm, humid areas, especially U.S. Gulf coast
Seasonal: warm months
Incubation period: 10 days
Signs & Symptoms: fever, headache, rash on chest and abdomen
Low mortality even in untreated


Orientia tsutsugamushi

Scrub typhus
Geography: Asia and southwest pacific
Vector: chiggers in sandy soil
reservoir: rodents
Incubation: 2 weeks
Signs & Symptoms: high fever, headache, myalgia, scab at bite, flat maculopapular rash develops


Borrelia burgdorferi

Spirochete- best place to look is in salivary glands
Lyme disease: most commonly reported tick borne illness in the U.S.
Vector: tick
Reservoir: white-footed mice, white-tailed deer
Geography: Northeast U.S.; Great Lakes region
Dx: EIA or IFA + then Western Blot; must have two positive tests; if negative results and signs and symptoms persist, then retest using convalescent serum


Stages of Borrelia burgdorferi

Stage 1: localized bulls-eye rash and flulike symptoms for 2-3 weeks

Stage 2: disseminated to the body causing fatigue, migratory joint, and muscle pain; sometimes goes undetected because no bulls eye rash at stage 1; polyarthralgia

Stage 3: chronic arthritis, encephalitis; lifetime disease


Relapsing Fever

2 types
1. Endemic Tick Borne with soft tick; 15 species of Borellia
2. Epidemic Louse Borne: Borellia recurrentis; reservoir are humans


Relapsing Fever: Endemic

15 species of Borrelia
occurs at low levels all the time
soft tick
Buzz words: rustic cabin that is in poor condition
relapses occur about 10 times before treatment is sought


Relapsing Fever: Epidemic

Borrelia recurrentis
Known as epidemic or louse borne relapsing fever
relapses occur once before treatment sought because many people have it at the time so it is more well known to others
Geography: Ethiopia, Rwanda, Chile
RBCs with spirochetes; big for a bacterium
Dx: microscopy of blood sample; cannot do serology to look for Ab because this organism has antigenic variation
Buzz words: louse born and relapsing fever (recurrent) until they seek treatment


Relapsing Fever: Antigenic Variation

The immune system will attack the bacteria to a point when it cannot be detected because the decrease in bacteria, and at this time it increases sweating due to the immune response and also the borrelia are now changing the proteins so the immune system cannot recognize it, then it turns into a cycle
Once they seek tx with antibiotics, this cycle will stop


Meningitis: Neonatal vs. Children/Adult Strains

Neonatal: group B Strep (S. agalactiae), E. coli, Listeria monocytogenes

Children/teens/adults: S. pneumoniae, Neisseria meningitides, Haemophilus influenzae type B

Main Virulence Factor: CAPSULE


Neonatal Meningitis

Vertical Transmission: from mother
group B Strep aka S. agalactiae: during birth
E. coli: during birth
Listeria: crosses the placenta

Strep agalactiae: Gram positive cocci; catalase negative; can be present in mom’s vaginal flora, so when the baby is being born that is how it can be transferred
E. Coli – from mother’s fecal matter
Listeria crosses the placenta and causes massive damage to the fetus and usually results with miscarriage

Signs and symptoms: nuchal rigiditiy, fever with cold hands and feet, vomiting/refusal to eat, blotchy skin, high pitched moan/cry, blank staring/expression, difficult to wake


Streptococcus agalactiae

causes meningitis
Gram positive cocci
Virulence factor: capsule
Normal flora of GI tract and vagina
CAMP: TSA agar with sheep blood; Staph aureus + agalactiae = increases β-hemolysis = positive result; forms an "arrowhead"

How is it differentiated from Strept pyogenes which is also beta-hemolytic and catalase negative?
S. agalactiae is resistant to bacitracin and S. pyogenes is sensitive


E. coli: meningitis

causes meningitis
Normal flora of GI tract
Most E. coli are non-pathogenic
Characteristics: gram negative rod, grows on MacConkey agar, ferments lactose, indole positive
For the strains that cause meningitis, capsule is very important: K antigen


Listeria monocytogenes

Gram positive rod, facultative, intracellular pathogen, highly motile
2 types: 1. Flagella for extracellular movement
2. Actin tails from eukaryotic actin (intracellular)

Normally found in soil, vegetation, water and intestinal tract of many animals
Able to grow and multiply at low temps: 1 to 45 degrees C; aka can grow in the refrigerator



Pregnant women: vertical transmission: ingestion; flu-like illness and crosses the placenta
Fetus: transplacental transmission, highly fatal, stillbirth
Newborns: during birth, neonatal meningitis

Transmission: ingestion of contaminated food
Must ingest large numbers to result in infection
Milk- raw/unpasteurized, soft cheeses, cold cuts, hotdogs, raw vegetables, coleslaw
Current major outbreak: cantaloupes; killed several
Incubation period: 11-70 days, ave.31 days


Listeria Pathogenesis

Invade M cells like salmonella and EIEC
Escape phagosome
Use actin tail for motility
ActA protein forms the actin tail
Infect adjacent cells
Avoids immune system


Listeria Dx

Culture: Cold enrichment set at 4 degrees C
Weakly b hemolytic, better with S. aureus
CAMP test: listeria + staph aurues


Bacterial Meningitis: Children/Adults

Photophobia, drowsiness/confusion, fitting/seizures, joint pain, nuchal rigidity, headache, fever, and vomiting
Neisseria meningitidis
Haemophilus influenzae type B
S. pneumoniae


Neisseria Species

gram negative, diplococci, aerobic, non-motile, fastidious, capnophilic: 5% CO2
N. gonorrhoeae- causes gonorrhea
N. meningitidis- causes meningitis
Buzz words: kidney bean/coffee bean shaped

N. gonorrhoeae vs. meningitides - meningitidis ferments maltose and glucose, but gonorrhoeae ferments ONLY glucose


Neisseria Virulence Factors

N. meningitidis: CAPSULE
N. gonorrhoeae: pili most important for antigenic variation
Pili, Por proteins (outer membrane), Opa proteins, LOS (instead of LPS), Rmp proteins, IgA protease, and capsule


N. meningitidis Infections

Low prevalence, high mortality
If untreated, mortality rate close to 100%, with treatment 10%
Approximately 20% of the population are healthy carriers
Seasonal: winter
Transmission: Respiratory droplets
Viral meningitis is more common and less deadly
Bacterial meningitis is less common and more deadly
Need to know viral vs. bacterial so you know how to treat the patient appropriately
The vaccine does not cover type B… most colleges require the vaccine


Pathogenesis of Neisseria

transmission, attach and invade mucosal cells (via pili, PorA, PorB, Opa, capsule), multiply within mucosal cells, move into subepithelial space, LOS stimulates TNF alpha symptoms like fever


N. meningitidis High Risk Groups and Symptoms

High Risk Groups: infants 6months-2 years because under 6 months protected by maternal antibodies, army recruits, college students living in residence halls, complement deficiency (immunodecificent)

Symptoms: sudden onset of severe headache, fever, *neck stiffness*, irritability, *photophobia*, malaise, nausea/ vomiting



Invasion of the bloodstream, sepsis, thrombosis of small blood vessels
Symptoms: fever, chills, arthralgia, muscle pain, petechial rash
very similar to gonoccemia, therefore must do additional testing (maltose vs. glucose fermentation)


N. meningitidis Dx

Diagnosis: spinal tap, Gram stain of CSF
Meningococcemia: Gram stain of blood
Culture on: Thayer-Martin agar (chocolate agar with antibiotic on it so nothing else will grow other than Neisseria)
Chocolate: blood agar that has been heated/lysed before plated out and allowed to solidify


Meningitis vaccines

2 vaccines:

1. Meningococcal capsular polysaccharide vaccine
A, C, Y, & W135
Does not work in children < 2 yrs old or for type B strain

2. Meningococcal conjugate vaccine
Recommended for: college students, army recruits, splenectomy, travelers


Haemophilus influenzae

causes meningitis in adults/children
Characteristics: gram negative short fat rod, normal flora of the URT, capsule or no capsule (must have a capsule to cause meningitis), adhesins, endotoxin

1. Has capsule: Serotypes a-f, Haemophilus influenzae type b
Hib: 1987 vaccine available - for type B strain
causes: meningitis, epiglottitis
Unvaccinated children- at risk

2. No capsule: non-typeable, otitis media (inflammation of middle ear), sinusitis, bronchitis, pneumonia