Infectious Disease I

Question 1

A PPD is considered positive in HIV patients if the induration size is > […] mm.

Answer 1

A PPD is considered positive in HIV patients if the induration size is > 5 mm.

may be false-negative in patients with CD4+ counts < 200/mm3

Question 2

Antibiotic prophylaxis in HIV patients with CD4+ count < 50/mm3 should include […] (MAC) and […] (PCP, toxoplasma).

Answer 2

Antibiotic prophylaxis in HIV patients with CD4+ count < 50/mm3 should include azithromycin (MAC) and TMP-SMX (PCP, toxoplasma).

Question 3

How do humans typically contract an Echinococcus granulosus infection?

Answer 3

Consumption of food or water contaminated with dog feces

sheep are the intermediate host

Question 4

How is cutaneous larva migrans typically acquired (mode of transmission)?

Answer 4

Walking barefoot on contaminated sand or soil

Question 5

How is the diagnosis of mucormycosis established?

Answer 5

sinus endoscopy with biopsy & culture

Question 6

In addition to empiric antibiotics, what other medication should be administered to patients with suspected bacterial meningitis?

Answer 6

Corticosteroids

helps prevent the neurological deficits associated with pneumococcal meningitis (e.g. deafness, focal deficits); should be discontinued if pneumococcal meningitis is ruled out

Question 7

In areas with high rates of chloroquine-resistant malaria, chemoprophylaxis typically includes […], […], or […].

Answer 7

In areas with high rates of chloroquine-resistant malaria, chemoprophylaxis typically includes atovaquone-proguanil, doxycycline, or mefloquine

e.g. Africa, Asia (including India), and Oceania

Question 8

In healthy adults, acute hepatitis B infection is self-limited in > […]% of cases.

Answer 8

In healthy adults, acute hepatitis B infection is self-limited in > 90-95% of cases.

Question 9

In the United States, a PPD is considered negative in healthy patients with low likelihood of TB if the induration size is […].

Answer 9

In the United States, a PPD is considered negative in healthy patients with low likelihood of TB if the induration size is 15 mm.

the cutoff for intermediate-risk patients (e.g. healthcare workers, recent immigrants) is < 10 mm

Question 10

In the United States, a PPD is considered positive in those with high risk of TB if the induration size is > […] mm (e.g. immunosuppressed patients, recent contacts of known TB case).

Answer 10

In the United States, a PPD is considered positive in those with high risk of TB if the induration size is > 5 mm (e.g. immunosuppressed patients, recent contacts of known TB case).

Question 11

In the United States, a PPD is considered positive in those with intermediate risk of TB if the induration size is > […] mm (e.g. healthcare workers, IVDA, recent immigrants).

Answer 11

In the United States, a PPD is considered positive in those with intermediate risk of TB if the induration size is > 10 mm (e.g. healthcare workers, IVDA, recent immigrants).

Question 12

Indications for corticosteroid use in Pneumocystis pneumonia treatment (in addition to TMP-SMX) include PaO2 […] mmHg.

Answer 12

Indications for corticosteroid use in Pneumocystis pneumonia treatment (in addition to TMP-SMX) include PaO2 < 70mmHg or A-a gradient > 35 mmHg.

also indicated if SaO2 < 92%

Question 13

Infection with Vibrio vulnificus causes severe infection in patients who have […] disease (organ).

Answer 13

Infection with Vibrio vulnificus causes severe infection in patients who have liver disease (organ).
e.g. cirrhosis, hepatitis, hemochromatosis

Question 14

One symptom associated with bacterial endocarditis is septic arterial or pulmonary […].

Answer 14

One symptom associated with bacterial endocarditis is septic arterial or pulmonary emboli.

mnemonic: FROM JANE; may cause various nodes/lesions associated with bacterial endocarditis

Question 15

One symptom associated with bacterial endocarditis is […], which occurs as a result of increased release of hepcidin.

Answer 15

One symptom associated with bacterial endocarditis is anemia of chronic disease, which occurs as a result of increased release of hepcidin.

mnemonic: FROM JANE; ACD is a microcytic anemia with high ferritin and low serum iron

Question 16

One symptom associated with bacterial endocarditis is […], which are small, nontender, erythematous lesions on the palm or sole.

Answer 16

One symptom associated with bacterial endocarditis is Janeway lesions, which are small, nontender, erythematous lesions on the palm or sole.

mnemonic: FROM JANE

Question 17

One symptom associated with bacterial endocarditis is […], which occurs as blood flows over vegetations on the heart valve.

Answer 17

One symptom associated with bacterial endocarditis is murmur, which occurs as blood flows over vegetations on the heart valve.

mnemonic: FROM JANE

Question 18

One symptom associated with bacterial endocarditis is […], which are tender, raised lesions on the finger or toe pads.

Answer 18

One symptom associated with bacterial endocarditis is Osler nodes, which are tender, raised lesions on the finger or toe pads.

Question 19

One symptom associated with bacterial endocarditis is […], which are round, white spots on the retina surrounded by hemorrhage.

Answer 19

One symptom associated with bacterial endocarditis is Roth spots, which are round, white spots on the retina surrounded by hemorrhage.

mnemonic: FROM JANE

Question 20

One symptom associated with bacterial endocarditis is […] in the nail bed.

Answer 20

One symptom associated with bacterial endocarditis is splinter hemorrhages in the nail bed.

mnemonic: FROM JANE; occurs due to embolization of septic vegetations

Question 21

Osteomyelitis in diabetic patients is typically preceded by a long-standing foot ulcer that spreads […] to bone, causing a […]-microbial infection.

Answer 21

Osteomyelitis in diabetic patients is typically preceded by a long-standing foot ulcer that spreads contiguously to bone, causing a poly-microbial infection.

Question 22

Patients who received blood transfusions before […] should be screened for hepatitis C.

Answer 22

Patients who received blood transfusions before 1992 should be screened for hepatitis C.

do you need to memorize the year? probably not… suspend this card if you want 3

Question 23

Patients with HIV who present with an AIDS defining illness secondary to lack of anti-retroviral therapy should be initiated on HAART […] after treatment of the infection.

Answer 23

Patients with HIV who present with an AIDS defining illness secondary to lack of anti-retroviral therapy should be initiated on HAART two weeks after treatment of the infection.

to prevent immune reconstitution syndrome

Question 24

Patients with suspected aspiration pneumonia should be treated with antibiotics that include […] coverage.

Answer 24

Patients with suspected aspiration pneumonia should be treated with antibiotics that include anaerobic coverage.

e.g. clindamycin, metronidazole + amoxicillin, amoxicillin-clavulanate

Question 25

Severe Vibrio vulnificus infection is more common in those with liver disease, especially [...].

Answer 25

Severe Vibrio vulnificus infection is more common in those with liver disease, especially **hereditary hemochromatosis**. iron acts as a growth catalyst for the organism

Question 26

What anti-malarial drug is used to prevent dormant hepatic hypnozoites in patients infected with Plasmodium vivax?

Answer 26

Primaquine

Question 27

What antibody is typically positive during the window phase of hepatitis B infection?

Answer 27

IgM anti-HBc

Question 28

What are the indications for sequential PCV13 vaccine, followed by PPSV23 vaccine 6-12 months later, in adults?

Answer 28

age \> 65 or very high risk patients \< 65 (e.g. asplenia, cochlear implants, immunocompromised, CKD)

Question 29

What are the indications for the PPSV23 vaccine, alone, in adults?

Answer 29

age \< 65 with other chronic medical conditions (e.g. heart/lung/liver disease, diabetes, smoking)

Question 30

What are the recommendations regarding live attenuated virus vaccination (e.g. MMR, zoster, varicella) in HIV patients?

Answer 30

Vaccinate if CD4+ counts \> 200/mm3 and titers are low

Question 31

What are the recommended empiric antibiotics for immunocompromised patients with suspected bacterial meningitis?

Answer 31

vancomycin + ampicillin + cefepime provides coverage for major organisms of bacterial meningitis and pseudomonas (cefepime), Listeria (ampicillin), and cephalosporin-resistant pneumococci (vancomycin); ampicillin is also added for patients \> 50 years of age

Question 32

What are the two most common causes of secondary bacterial pneumonia?

Answer 32

Streptococcus pneumoniae and Staphylococcus aureus typically presents with worsening fever and pulmonary symptoms after initial symptomatic improvement

Question 33

What autoimmune antibody may be elevated in patients with infective endocarditis?

Answer 33

Rheumatoid factor rheumatoid factor is a non-specific finding; don't let it throw you off the diagnosis if symptoms otherwise point to infective endocarditis!

Question 34

What bacteria is the most common cause of community-acquired bacterial meningitis?

Answer 34

Streptococcus pneumoniae treatment typically involves vancomycin and a third-generation cephalosporin +/- ampicillin

Question 35

What combined antiviral therapy is effective against most strains of hepatitis C (e.g. genotypes 1-6)?

Answer 35

Sofosbuvir-velpatasvir HCV genotyping should be done prior to initiation of antiviral therapy

Question 36

What enzyme is often elevated in patients with Pneumocystis pneumonia?

Answer 36

LDH other indications of PCP pneumonia include hypoxia (PaO2 \< 75 mmHg) and diffuse, bilateral infiltrates on CXR

Question 37

What is the diagnostic test of choice for patients with suspected leprosy?

Answer 37

Skin biopsy from the edge of a lesion

Question 38

What is the diagnostic test of choice for patients with suspected Pneumocystis pneumonia without an adequate induced sputum sample?

Answer 38

Bronchoalveolar lavage

Question 39

What is the empiric treatment for ehrlichiosis?

Answer 39

Doxycycline

Question 40

What is the initial treatment of choice for most patients with early localized Lyme disease?

Answer 40

Oral doxycycline amoxicillin or cefuroxime may be used in children \< 8 years old and pregnant women, where doxycycline is contraindicated

Question 41

What is the like causative organism in an HIV patient with a CD4+ count of 85/mm3 that presents with three weeks of copious, watery diarrhea and low-grade fever?

Answer 41

Cryptosporidium

Question 42

What is the likely causative microorganism in a patient with infective endocarditis after having a tooth extraction one month ago?

Answer 42

Viridans group streptococci

Question 43

What is the likely causative microorganism in a renal transplant patient that develops fever, progressive dyspnea on exertion, abdominal pain, bloody diarrhea, and elevated LFTs?

Answer 43

Cytomegalovirus solid organ transplant patients that develop systemic illness involving multiple organ systems (e.g. pneumonitis, gastroenteritis, hepatitis) likely have CMV; versus PCP, which presents primarily with pulmonary symptoms

Question 44

What is the likely causative microorganism in an alcoholic sailor that develops high-grade fever hours after cutting his foot while sailing in the ocean? The cut is surrounded by erythema and dark-colored bullae with streaking erythema extending proximally up the limb.

Answer 44

Vibrio vulnificus V. vulnificus is found in marine environments and causes severe disease (e.g. rapidly progressive septicemia, necrotizing fasciitis) in patients with liver disease

Question 45

What is the likely causative organism in a male that presents with dysuria, urinary frequency, and mucopurulent discharge? Gram stain and urine culture are negative.

Answer 45

Chlamydia trachomatis gram stain shows gram-negative cocci in 95% of cases of gonoccocal arthritis

Question 46

What is the likely causative organism in a patient that develops osteomyelitis after stepping on a rusty nail? The nail pierced the patient's shoes and pierced the heel.

Answer 46

Pseudomonas aeruginosa Staph aureus and Pseudomonas are responsible for most deep infections following puncture wounds; the sole of a shoe (warm, moist) is a hospitable environment for Pseudomonas

Question 47

What is the likely causative organism in a patient that presents with fever and mild pharyngeal erythema without lymphadenopathy? A heterophile antibody test is negative.

Answer 47

Cytomegalovirus CMV can cause a mononucleosis-like illness (resembling EBV) but with mild/absent pharyngitis, lymphadenopathy, and splenomegaly and a negative heterophile antibody test

Question 48

What is the likely causative organism in a patient who develops infective endocarditis after having a recent cystoscopy for persistent dysuria?

Answer 48

Enterococci (e.g. Enterococcus faecalis)

Question 49

What is the likely causative organism in a patient with poorly controlled HIV that presents with large, reddish pedunculated skin lesions that bleed easily? CT scan of the abdomen reveals hypodense liver lesions that enhance with IV contrast.

Answer 49

Bartonella quintana the patient likely has bacillary angiomatosis (pedunculated/exophytic lesions and liver involvement are more typical of BA than Kaposi sarcoma); treatment typically includes doxycycline or erythromycin

Question 50

What is the likely causative organism in an HIV patient with a CD4+ count of 30/mm3 that presents with one month of fever, intermittent bloody diarrhea, abdominal pain, and weight loss?

Answer 50

Cytomegalovirus (CMV) diagnosis is confirmed with colonoscopy + biopsy; HIV patients with active CMV disease require ocular exam to rule out concurrent retinitis

Question 51

What is the likely causative organism in an immunocompromised patient with multiple lung cavitary lesions and brain abscesses identified on imaging? Sputum cultures grow partially acid-fast, gram-positive, branching rods.

Answer 51

Nocardia

Question 52

What is the likely causative organism in an IV drug user that presents with three days of fever, pleuritic chest pain, and shortness of breath? Chest imaging reveals multiple nodular lesions with small cavities.

Answer 52

Staphylococcus aureus likely due to septic emboli from tricuspid endocarditis

Question 53

What is the likely chief complaint in a patient diagnosed with Cryptosporidium parvum infection?

Answer 53

Prolonged, profuse, watery diarrhea (typically 10 - 14 days) Traveler's diarrhea that is prolonged, profuse, and watery is often due to a parasitic pathogen; patients may also complain of nausea, abdominal pain, low-grade fever, or malaise

Question 54

What is the likely diagnosis and causative organism in a patient that presents with a 1-day history of fever and a warm, tender, erythematous rash with raised, well-demarcated borders?

Answer 54

Erysipelas; Streptococcus pyogenes (group A strep)

Question 55

What is the likely diagnosis in a college student with a recent viral URI that presents with high-grade fever, productive cough with hemoptysis, and leukopenia? CXR reveals bilateral alveolar infiltrates and multiple cavitations.

Answer 55

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection CA-MRSA has a predilection for young patients with recent influenza

Question 56

What is the likely diagnosis in a hemodynamically unstable patient that presents with fever, vomiting, and a diffuse, confluent maculopapular rash on the trunk and extremities? The patient recently had anterior packing in the emergency department for a nose bleed.

Answer 56

Toxic shock syndrome secondary to Staphylococcus aureus, likely due to unremoved nasal packing

Question 57

What is the likely diagnosis in a HIV patient from Missouri with a CD4+ count of 50/mm3 that presents with cough/dyspnea, mouth ulcers, and diffuse lymphadenopathy? Laboratory exam reveals pancytopenia and elevated LFTs.

Answer 57

Disseminated histoplasmosis seen in patients with CD4+ counts \< 100/mm3; characterized by prominent pulmonary, mucocutaneous, and reticuloendothelial manifestations

Question 58

What is the likely diagnosis in a landscaper with a finger ulceration, draining an odorless discharge, that spread to include similar nodules along the forearm? There is no lymphadenopathy on physical exam.

Answer 58

Sporotrichosis dimorphic fungus typically found in decaying plant matter/soil; no lymphadenopathy helps rule out other diagnoses (e.g. cat scratch fever)

Question 59

What is the likely diagnosis in a patient that developed sudden-onset abdominal pain, nausea, and vomiting after returning from a hike and eating leftover Chinese food?

Answer 59

Bacillus cereus food poisoning characterized by rapid symptom onset (1 - 6 hours) due to preformed enterotoxin; vomiting is the primary manifestation

Question 60

What is the likely diagnosis in a patient that emigrated from Southeast Asia and presents with a well-circumscribed, hypopigmented patch on the arm with no sensation to pinprick? The ulnar nerve on ipsilateral arm is thickened and tender.

Answer 60

Leprosy leprosy typically affects the skin and peripheral nerves

Question 61

What is the likely diagnosis in a patient that presents in the winter with abrupt onset high-grade fever, headache, and severe myalgias? No lymphadenopathy or abnormal lung sounds are appreciated on physical exam.

Answer 61

Influenza

Question 62

What is the likely diagnosis in a patient that presents with an intensely pruritic lesion on the foot (picture below)?

Answer 62

Cutaneous larva migrans typically begins as a pruritic, papular lesion at the entry site, followed by intensely pruritic, migrating, serpiginous reddish-brown tracks; ivermectin is typically given to speed resolution and clearance

Question 63

What is the likely diagnosis in a patient that presents with fever, sore throat, drooling, and muffled voice with pooled secretions visible in the oropharynx? There is no visible swelling of the floor of the mouth.

Answer 63

Epiglottitis most commonly due to H. influenzae type B, especially in unvaccinated individuals

Question 64

What is the likely diagnosis in a patient that presents with fever, sore throat, drooling, and muffled voice? The bilateral submandibular area is tender and indurated with palpable crepitus.

Answer 64

Ludwig angina rapidly progressive cellulitis of the submandibular space, usually due to dental infections; treatment involves IV antibiotics and removal of the inciting tooth

Question 65

What is the likely diagnosis in a patient that presents with flu-like symptoms without a rash after being bitten by a tick two weeks ago? Laboratory exam reveals leukocytosis, thrombocytopenia, and signs of hemolytic anemia.

Answer 65

Babesiosis Lyme disease and Rocky Mountain spotted fever are less likely given the absence of rash; Erlichiosis is less likely given the leukocytosis and signs of intravascular hemolysis