Infectious Disease

Question 1

Sporotrichosis

Answer 1

The initial lesion of lymphocutaneous sporotrichosis is a reddish nodule that later ulcerates and appears at the site of a thorn prick or other skin injury.

From the site of inoculation, the fungus spreads along the lymphatics forming additional subcutaneous nodules and ulcers.
Definitive diagnosis is made by culture,

Itraconazole is the drug of choice for treatment

Question 2

Disseminated gonococcal infection

Answer 2

Manifestation
Purulent monoarthritis
OR
Triad of tenosynovitis, dermatitis, migratory polyarthralgia

Diagnosis
A)Detection of Neisseria gonorrhoeae in urine, cervical, or urethralsample

B)Culture of blood, synovial fluid (less sensitive)

Treatment
3rd-generation cephalosporin intravenously

Question 3

Meningitis exposure prophylaxis

Answer 3

Regardless of vaccination status, healthcare workers (with close proximity and prolonged duration or exposure to respiratory secretions) and close contacts of infected patients with meningococcal disease should receive antibiotic chemoprophylaxis, ideally within the first 24 hours of patient diagnosis. Recommended regimens include rifampin, ciprofloxacin, or ceftriaxone

Question 4

Lemmiere’s syndrome
Signs and symptoms

Answer 4

-Recent sore throat
-Persistent fever and systemic symptoms while taking appropriate
antibiotic therapy for sore throat
-Neck pain and swelling
-Septic embolism

Question 5

Lemmiere’s syndrome
Lab results

Answer 5

WBC > 15,000 cells/µl

Chest x-ray and/or CT may show evidence of pulmonary emboli

Neck CT shows internal jugular thrombophlebitis

Infection is usually caused by the anaerobic bacterium Fusobacterium necrophorum.

Question 6

Lemmiere’s syndrome treatment

Answer 6

Treatment usually involves 4 weeks of antibiotics that have anaerobic coverage, such as beta-lactams with beta-lactamase inhibitors (e.g., ampicillin-sulbactam), clindamycin, or carbapenems

Question 7

Influenza prophylaxis

Answer 7

Identification of cases of influenza within a long-term care facility should prompt early institution of prophylactic antiviral therapy to all residents (even those previously vaccinated) during the outbreak.

Question 8

Strongyloidiasis clinical presentation

Answer 8

• Can be asymptomatic with peripheral eosinophilia

Gastrointestinal

• Abdominal pain mimicking duodenal ulcer, but pain worse with eating

• Chronic enterocolitis and malabsorption with high worm burden

Pulmonary

• Migration or larvae can cause dry cough, hemoptysis, dyspnea, and wheezing (often misdiagnosed as asthma)

• Fever with mild pneumonitis (can resemble pneumonia)

Skin

• Serpiginous and raised erythematous track (larva currens or “running” larva)

• Severe pruritus (ground itch)

Hyperinfection syndrome (due to autoinfection) leading to multiorgan dysfunction and possible septic shock.

Question 9

Strongyloidiasis diagnostic test

Answer 9

• Stool samples can confirm but are frequently negative

• Many patients require serology tests (ELISA IgG antibody), endoscopy for duodenal biopsy or aspirate, or string test (Entero-Test)

Question 10

Strongyloidiasis treatment

Answer 10

1st line: Ivermectin
2nd line: Albendazole

Question 11

Syphilis post exposure prophylaxis

Answer 11

A patient exposed within 90 days of diagnosis of primary, secondary, or early latent syphilis in a sex partner

⏩⏩should receive treatment (even if the patient is seronegative for syphilis).

A patient exposed >90 days after diagnosis of primary, secondary, or early latent syphilis in a sex partner

⏩⏩should undergo serologic testing and also receive treatment if results are not immediately available or follow-up is uncertain.

Question 12

MAC introduction

Answer 12

-Mycobacterium avium complex (MAC) is the most common cause of non- tuberculous mycobacteria (NTM) disease.
-MAC is ubiquitous and can be found in aerosolized water, piped hot water systems (eg, household and hospital water supplies, bathrooms), house dust, soil, birds, and farm animals.
-It can contaminate or colonize patients’ sputum, especially in those who are immunocompromised or with underlying lung disease (eg, chronic obstructive pulmonary disease [COPD]).

Question 13

MAC presentation and diagnosis

Answer 13

The presentation can be similar to M tuberculosis (MTB) infection, and sputum can stain positive for acid-fast bacilli.
The diagnosis requires
1)clinical (chest x-ray with nodular or cavitary lesions, or CT with multifocal bronchiectasis and nodules)

2)microbiologic (>2 positive sputum cultures for MAC, 1 positive culture from bronchial wash/lavage, or lung biopsy with consistent findings and positive culture) criteria with the exclusion of other relevant conditions.

Question 14

MAC treatment

Answer 14

Treatment in confirmed cases includes at least a year of combination therapy with a macrolide (eg, clarithromycin, azithromycin), ethambutol, and a rifamycin (eg, rifampin, rifabutin).

Question 15

HSV encephalitis
Presentation

Answer 15

• Rapid onset (<1 week) of fever & headache
• Focal neurologic deficits (eg, cranial nerve palsies, hemiparesis, ataxia)
• Mental status changes & seizures

Question 16

HSV encephalitis
Investigation

Answer 16

• CSF may be HSV PCR positive & show lymphocytic pleocytosis
• CT or MRI may be normal or show temporal lobe abnormalities
• EEG with high amplitude slow waves in >80% of patients

Question 17

Invasive aspergillosis

Answer 17

Typically occurs in the setting of a severely immunocompromised state.
Patients commonly have fever, pleuritic chest pain, and hemoptysis; imaging often reveals nodular disease with ground-glass opacities (Halo sign) or cavitary lesions with air fluid levels (Air crescent sign). Diagnosis is usually made with sputum fungal stain and culture and serum fungal biomarkers (eg, galactomannan, beta-D-glucan).
A positive serum galactomannan assay has a specificity >75%.
Treatment with Voricanazole.

Question 18

Acute radiation pneumonitis

Answer 18

Patients receiving thoracic or neck irradiation are at risk for acute radiation pneumonitis, which usually presents with antibiotic-nonresponsive pneumonia 4-12 weeks after radiation exposure. Treatment for acute disease includes prednisone for 2 weeks followed by a gradual taper over 3-12 weeks.

Question 19

Legionella clues

Answer 19

Exposure history
• Recent travel (especially cruise or hotel stay) within the previous 2 weeks
• Contaminated potable water in hospitals/nursing homes

Clinical presentation
• Fever >39 C (102.2 F)
• Bradycardia relative to high fever
• Neurologic symptoms (especially confusion)
• Gastrointestinal symptoms (especially diarrhea)
• Unresponsive to ẞ-lactam & aminoglycoside antibiotics

Labs
• Hyponatremia
• Hepatic dysfunction
• Hematuria & proteinuria
• Sputum Gram stain showing many neutrophils but few or no microorganisms

Question 20

Hepatitis A post exposure prophylaxis

Answer 20

Postexposure prophylaxis for hepatitis A is indicated as soon as possible in all unvaccinated household contacts including adults < age 40 and children > age 12 months. The hepatitis A virus vaccine is preferred over immune globulin in these patients;

immune globulin is recommended in children < 12 months and immunocompromised individuals.

Question 21

Measles presentation

Answer 21

Measles infections tend to begin with fever, malaise, and anorexia followed by the “3 Cs” of cough, conjunctivitis, and coryza. Koplik spots (white lesions on an erythematous base) then form on mucous membranes, followed by the characteristic exanthem (maculopapular rash that spreads in a cephalocaudal and centrifugal manner). Measles is highly infectious and transmitted by droplet nuclei, so airborne isolation is required for 24 days after rash onset.

Question 22

Cryptococcal meningitis in HIV
Treatment

Answer 22

Induction: 2weeks
Ampho B + Flucytosine (recommended)
Ampho B + Fluconazole (alternative)

Consolidation: 8weeks
Fluconazole 800mg daily

Maintenance: at least 1 year
Fluconazole 200mg daily

Serial LP for high ICP

Question 23

Infective endocarditis surgery indication

Answer 23

Valvular or conduction failure
1) Acute heart failure due to valvular regurgitation
2) Valve leaflet fistula formation
3) New heart block

Uncontrollable infection
1) Paravalvular abscess formation
2) Infection with difficult-to-treat pathogen (eg, fungi)
3) Persistent fever or bacteremia despite antibiotics for >7 days

Embolic complications
1) Systemic emboli despite appropriate antibiotics
2) Left-sided, mobile vegetation >10 mm & prior embolic event

Question 24

Skin abscess treatment

Answer 24

The foundation of treatment is incision and drainage, but empiric antibiotics should be considered for those with:
-An abscess ≥2 cm
-Extensive surrounding cellulitis
-Systemic signs of infection (eg, fever, chills, tachycardia, leukocytosis)
-Neutropenia
-Multiple abscesses
-Extremes of age
-Lack of response to incision and drainage

For these individuals, the debrided material from incision and drainage should be sent for Gram stain and culture.
Empiric treatment with oral trimethoprim- sulfamethoxazole or doxycycline is generally curative.

Question 25

Cat scratch disease

Answer 25

Cat-scratch disease most often occurs in immunocompetent children and young adults and is caused by inoculation of the fastidious gram-negative bacterium Bartonella henselae after the scratch or bite of a kitten or cat.

Although cat-scratch disease is usually a self-limited illness, some experts recommend a short course of treatment with azithromycin. Other agents that can be used include doxycycline, rifampin, clarithromycin, trimethoprim-sulfamethoxazole, and ciprofloxacin.

Question 26

Traveler’s diarrhea

Answer 26

Antibiotic prophylaxis to prevent travelers’ diarrhea is not recommended for most travelers but can be considered for high-risk travelers

Include Persons with chronic inflammatory bowel disease (Crohn and ulcerative colitis) or who are immunocompromised (HIV, organ transplantation, those taking immunosuppressant medication) are particularly susceptible

Question 27

Infection of a cardiovascular implantable electronic device (CIED).

Indication for device removal

Answer 27

Appropriate management of a known or suspected CIED infection involves removal of the entire device (generator and leads) if any of the following are present:

1) Evidence of valve or lead vegetation on transesophageal echocardiogram (TEE)

2) Positive blood cultures with an organism with high propensity for causing infective endocarditis (eg, Staphylococcus, Streptococcus, or Candida spp)

3) Evidence of pocket infection, including localized pain/tenderness, erythema, swelling, purulent drainage, or skin erosion

Question 28

Infection of a cardiovascular implantable electronic device (CIED).

Antibiotics management

Answer 28

In patients with suspected endocardial involvement device removal should be followed by appropriate antibiotic treatment for infective endocarditis (eg, 6 weeks of therapy).

Patients with CIED pocket infection but no evidence of endocardial involvement (eg, those with negative blood cultures and unremarkable TEE) can receive 2 weeks of antibiotic therapy following device removal.

When needed, reimplantation of a new CIED is performed on the contralateral side of the chest once appropriate source control of the infection is achieved.

Question 29

Tuberculin skin test
Booster effect/ window period

Answer 29

window period from infection to detectable skin test reactivity is generally 2-12 weeks. As a result, the Centers for Disease Control and Prevention recommends repeat TST testing 8-12 weeks after exposure for those with negative initial TST.

• Patients whose repeat TST is negative are cleared.

Those with positive TST require further evaluation for active TB with symptom review and chest x-ray.

A similar approach would apply for interferon gamma release assays, which appear to have a window period of 4-6 weeks

Question 30

West nile virus

Answer 30

West-Nile virus is a mosquito-borne disease that mainly occurs during the summer months, especially when the weather is humid. Encephalitis associated with acute asymmetric flaccid paralysis or extrapyramidal symptoms is highly suggestive of West-Nile virus infection. The diagnosis is confirmed with positive serum or CSF IgM titer for West Nile virus. Treatment is mainly supportive.

Question 31

Hot tub pneumonitis

Answer 31

Patients with hot tub/spa exposure are at risk for Mycobacterium avium complex infection and can present with hypersensitivity pneumonitis (“hot tub lung”). Manifestations are often acute and resemble an influenza infection. Most cases are self- limited and resolve with supportive care; a short course of prednisone can be used if symptoms do not resolve.

Question 32

Clinical manifestations of typhoid fever

Answer 32

Week 1
• Rising fever
• Bacteremia
• Relative bradycardia (pulse-temperature dissociation)
Week 2
• Abdominal pain
• Rose spots on trunk & abdomen
Week 3
• Hepatosplenomegaly
• Intestinal bleeding & perforation

Question 33

Actinomycosis

Answer 33

Cervicofacial actinomycosis most commonly presents in the mandibular region as a slowly growing, non-tender mass with characteristic sulfur granules. The infection can extend through tissue planes and form abscesses, fistulas, and draining sinus tracts. Diagnosis is confirmed by culture

Treatment
Intravenous penicillin for 4-6 weeks is preferred initially, followed by 6 to 12 months of oral penicillin. For patients with penicillin allergy, clindamycin is a reasonable alternative. Surgical excision may be required for more severe cases.

Question 34

Chagas disease

Answer 34

Chagas disease is the leading cause of dilated cardiomyopathy in Central and South America. It is caused by Trypanosoma cruzi infection and is characterized by myocarditis progressing to dilated cardiomyopathy, nonspecific electrocardiogram abnormalities including right bundle branch block and left anterior fascicular block, and development of left ventricular apical aneurysms.

Question 35

Schistosomiasis

Answer 35

Acute onset of fevers, allergic-type symptoms (urticarial lesions, angioedema), and robust eosinophilia in the setting of a recent trip to sub-Saharan Africa with freshwater exposure is suggestive of acute schistosomiasis syndrome

(Katayama fever). This is a systemic hypersensitivity reaction against schistosomal eggs and larvae, typically occurring 14-28 days after infection. Chest x-ray infiltrates may be present. Microscopic examination for schistosomiasis eggs and serologic testing may be negative in acute schistosomiasis. The episode is usually self-limiting (days to weeks), and management is with corticosteroids during the acute phase followed by antihelminthic therapy (eg, praziquantel) to prevent long-term sequelae of helminth infection (eg, hydronephrosis, bladder squamous cell carcinoma).

Question 36

Tattoo infections

Answer 36

The most common complications of tattoos are local skin infections from staphylococcal species and hypersensitivity reactions from metals in the ink. Disseminated infections and nontuberculous mycobacterial infections are less common.

Question 37

necrotizing fasciitis treatment based on organism

Answer 37

Empiric treatment: pip-tazo + vancomycin +/- Clindamycin
__________________________
🔴Doxycycline plus ceftazidime is recommended for treatment of Vibrio vulnificus-associated necrotizing fasciitis.

🔴Clostridium perfringens-associated necrotizing fasciitis and myonecrosis are treated with penicillin and clindamycin.

🔴Ciprofloxacin plus doxycycline is the anti- biotic regimen recommended for Aeromonas hydrophila- associated necrotizing skin and soft tissue infections.

Question 38

Common variable immunodeficiency (CVID)

Answer 38

• Common variable immunodeficiency increases the risk of upper and lower respiratory tract infections caused by encapsulated bacteria, Mycoplasma species, and respiratory viruses as well as chronic diarrhea caused by giardiasis or chronic norovirus infection.

• Common variable immunodeficiency can be diagnosed in persons with documented low IgG levels, impaired antibody production to pneumococcal or tetanus vaccines, and variably decreased IgA and IgM antibody levels.

Question 39

Vertebral osteomyelitis treatment

Answer 39

• Initiation of antibiotic therapy for uncomplicated hemodynamically stable vertebral osteomyelitis is based on culture results.

• Image-guided biopsy has a diagnostic yield of approximately 60% for vertebral osteomyelitis and should be used in patients with negative blood culture results.

🔴🔴 Indications to begin empiric antibiotic therapy include hemodynamic instability, epidural abscess, signs of spinal instability, and progressive neurologic deficit.

Question 40

Pelvic inflammatory disease

Answer 40

• In women with pelvic inflammatory disease, signs of severe systemic toxicity or an inability to tolerate oral antibiotics, pregnancy, tubo-ovarian abscess, inability to exclude a surgical emergency, and failed outpatient antibiotic therapy are indications for hospitalization and parenteral therapy

• Combination cefotetan or cefoxitin plus doxycycline or combination clindamycin plus gentamicin are the preferred parenteral antibiotic regimens for patients hospitalized with pelvic inflammatory disease.

Question 41

Definition of false positive HIV test results

Answer 41

• A positive result on the fourth-generation HIV-1/2 antigen/antibody combination assay but negative result on HIV antibody differentiation is tested for HIV RNA by nucleic acid amplification testing; if posi- tive, acute HIV infection is confirmed, and a negative result identifies a false-positive combination assay

Question 42

Traveler’s diarrhea prophylaxis

Answer 42

• Travelers’ diarrhea prophylaxis with rifaximin is rec- ommended in patients with underlying conditions that place them at higher risk of infection or disease complications (e.g., immune compromise, inflamma- tory bowel disease, chronic kidney disease).

Fluoroquinolones are not recommended for travelers’ diarrhea prophylaxis in patients at increased risk because of increasing safety concerns and bacterial resistance.

Question 43

Intestinal amebiasis treatment

Answer 43

Nitroimidazoles are the mainstay of therapy for E histolytica intestinal disease. Metronidazole, in particular, is recommended, although agents with longer half-lives, such as tinidazole, are also effective.

Paromomycin, an oral aminoglycoside, is a luminal agent that is effective against E. histolytica. It can prevent recurrent infection by eradicating intestinal cysts and is therefore indicated in this patient.

However, it is not appropriate as initial therapy and should not be given until after the initial course of metronidazole. Paromomycin and metronidazole both tend to cause adverse gastrointestinal effects and are thus not given together.

Question 44

Rabies post exposure prophylaxis after high risk animal bite

Answer 44

Immunocompetent patients who have not been previously vaccinated should receive four doses of vaccine on days 0, 3, 7, and 14 in addition to a single dose of rabies immunoglobulin on day 0

post exposure prophylaxis consisting of three primary elements

1 Wound care

2 Administration of rabies immunoglobulin. When the wound is visible, as much of the dose as is feasible should be infiltrated directly in and around the wound

3 Administration of rabies vaccine

Question 45

Malaria prophylaxis

Answer 45

Prophylaxis with doxycycline (or chloroquine or mefloquine) should continue for 4 weeks after the last exposure to malaria to eradicate any parasites that were maturing in the liver and might still be released into the bloodstream

Another frequently used malaria prophylactic, atovaquone-proguanil, acts on both blood-borne schizonts and hepatic schizonts (ie, parasites developing in the liver). As a result, atovaquone-proguanil can be discontinued one week after departure from a malaria-endemic region