Page 194 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

150 SEcTioN ii Microbiology ` microbiology—cliNical bacteriology Microbiology ` microbiology—mycology

Rickettsial diseases
and vector-borne
illnesses Treatment: doxycycline.
rasH commoN
Rocky Mountain Rickettsia rickettsii, vector is tick. Despite its Classic triad—headache, fever, rash (vasculitis).
spotted fever name, disease occurs primarily in the South Palms and soles rash is seen in Coxsackievirus
Atlantic states, especially North Carolina. A infection (hand, foot, and mouth disease),
Rash typically starts at wrists A and ankles and Rocky Mountain spotted fever, and 2° Syphilis
then spreads to trunk, palms, and soles. (you drive CARS using your palms and soles).
Typhus Endemic (fleas)—R typhi. Rickettsii on the wRists, Typhus on the Trunk.
Epidemic (human body louse)—R prowazekii.
Rash starts centrally and spreads out, sparing
palms and soles.
rasH rare
Ehrlichiosis Ehrlichia, vector is tick. Monocytes with MEGA berry—
morulae B (mulberry-like inclusions) in Monocytes = Ehrlichiosis
cytoplasm. Granulocytes = Anaplasmosis
Anaplasmosis Anaplasma, vector is tick. Granulocytes with
morulae C in cytoplasm.
Q fever Coxiella burnetii, no arthropod vector. Spores Q fever is caused by a Quite Complicated
inhaled as aerosols from cattle/sheep amniotic Bug because it has no rash or vector and its
fluid. Presents with headache, cough, causative organism can survive outside in its
influenza-like symptoms, pneumonia, possibly endospore form. Not in the Rickettsia genus,
in combination with hepatitis. Common cause but closely related.
of culture ⊝ endocarditis.
A B C

Mycoplasma Classic cause of atypical “walking pneumonia” Not seen on Gram stain. Pleomorphic A .
pneumoniae (insidious onset, headache, nonproductive Bacterial membrane contains sterols for
cough, patchy or diffuse interstitial infiltrate). stability. Grown on Eaton agar.
A
Occurs frequently in those <30 years old;
outbreaks in military recruits, prisons, colleges.
X-ray looks worse than patient. High titer of Mycoplasma gets cold without a coat (no cell wall).
cold agglutinins (IgM), which can agglutinate Can cause atypical variant of Stevens-
RBCs. Johnson syndrome, typically in children and
Treatment: macrolides, doxycycline, or adolescents.
fluoroquinolone (penicillin ineffective since
Mycoplasma has no cell wall).

FAS1_2019_03-Microbiology.indd 150 11/14/19 12:21 PM