Microbiology

Question 1

CMV: Pharmacology
What is the MOA of Foscarnet?

Answer 1

It directly inhibits both DNA polymerase in HSV and reverse transcriptase in HIV. It is a pyrophosphate analog that does not require intracellular activation.

Question 2

Uworld Pharmacology: Lyme disease
How do you treat Lyme disease?

Answer 2

Doxycycline or PCN-type abx (eg, ceftriaxone). Tx with ceftriaxone during the second, early disseminated phase, can prevent Late Lyme disease.

Question 3

Uworld Microbiology: Lyme disease
What organism causes Lyme disease, how is transmitted, where is it considered endemic?

Answer 3

Caused by the spirochete Borrelia burgdorferi, transmitted by the bite of an Ixodes tick. Endemic in the northeastern USA and Northern Europe.

Question 4

Uworld Pathophysiology: Lyme disease
Describe the series of phases in Lyme disease:

Answer 4

1. Early localized phase: Days to wks following exposure, patients experience flu-like symptoms and the characteristic cutaneous eruption, erythema chronic migraines (ECM- target lesion)
2. Early disseminated phase: Weeks or months later, there may be CNS (eg, facial palsy) and/or cardiac involvement (eg, AV Nodal Block)
3. Late Lyme disease: Occurring months to years post-exposure, is rare given abx for other indications. Asymmetric arthritis (mc single knee joint) and/or subacute encephalopathy with decreased memory, somnolence, and mood changes.

Question 5

Uworld: Toxoplasmosis encephalitis
Describe the setting of Toxoplasma encephalitis:

Answer 5

• exposure to cat feces with subsequent ingestion of Toxoplasma Gondii
• Reactivation in setting of immunosuppression
• Primarily AIDS with CD4 count < 100/mm^3

Question 6

Uworld: Toxoplasmosis encephalitis
Describe the clinical manifestations of Toxoplasma encephalitis:

Answer 6

• headache
• confusion
• fever
• focal neurological deficits/seizures

Question 7

Uworld: Toxoplasmosis encephalitis
Describe the diagnosis of Toxoplasma encephalitis:

Answer 7

• positive Toxoplasma Gondii IgG
• Multiple ring-enhancing brain lesions

Question 8

Uworld: Toxoplasmosis encephalitis
Describe the treatment of Toxoplasma encephalitis:

Answer 8

• Sulfadiazine and pyrimethamine (Leucovorin)
• antiretroviral initiation
• prophylaxis: TMP-SMX (CD4 count < 100/ mm^3)

Question 9

Infectious Disease: Hepatitis B
What is an essential step in the replication cycle in Hepatitis B virus?

Answer 9

Reverse transcription of template RNA to viral DNA

Question 10

Infectious Diseases: Catheter related bloodstream infection
What are the most common pathogens causing nosocomial bloodstream infections?

Answer 10

• coagulase-negative streptococci
• staphylococcus aureus
• enterococci
• candida species
  (commensal bacteria)

Question 11

Infectious Diseases: Catheter related bloodstream infection
What is the usual cause of blood stream infections?

Answer 11

Intravascular catheters

Question 12

Parasitology
Describe an infection caused by Clonorchis sinensis (Chinese liver fluke):

Answer 12

• endemic to Southeast Asia
• ingesting raw or undercooked freshwater fish
• causes biliary tract inflammation (cholangitis) that can turn recurrent
• pigmented (brown) gallstones
• increases the risk of cholangiocarcinoma

Question 13

Parasitology
Describe an infection caused by Ascaris lumbricoides (roundworm):

Answer 13

• asymptomatic, may experience respiratory symptoms and GI distress causing Loeffler syndrome or bowel obstruction at the ileocecal valve.
• fecal oral transmission
• not commonly associated with cholangitis or pigment gallstone formation

Question 14

Parasitology
Describe an infection caused by Dibothriocephalus lotus (former Diphyllobothrium latum) aka fish tapeworm:

Answer 14

• transmits by ingesting raw or undercooked freshwater fish
• asymptomatic, chronic infection can lead to vitamin b12 deficiency so a megaloblastic anemia can develop with neurological symptoms.

Question 15

Parasitology
Describe an infection caused by Schistosome haematobium aka trematode:

Answer 15

• penetrates the skin and enters systemic circulation
• intermediate hosts are freshwater snails
• chronic infection inclue GU symptoms (hematuria, dysuria) and an increased risk of Squamous cell carcinoma of the bladder
• Sch. Mansoni and Sch. japonicum can lead to schistomiasis, which presents with diarrhea and abdominal pain

Question 16

Parasitology
Describe an infection caused by Trichuris trichiura aka whipworm):

Answer 16

• fecal oral transmission of eggs
• diarrhea, iron deficiency anemia, growth delay, or rectal prolapse

Question 17

Bootcamp: Mycology: Fungal Infectious Conditions- Dermatology
Pt with a round, pruritic, scaly lesion with central clearing is consistent with what?
How would you definitively diagnose?

Answer 17

• Dx: Tinea corporis aka “ringworm” caused by dermatophytes like Trichophyton, Epidermophyton, and Microsporum
• Definitive diagnose increased a KOH prep

Question 18

Bootcamp: Systemic infections
Pt presents with flu-like symptoms, regional lymphadenopathy, and eyrthematous lesion, pain/inflammation and has pets.
What is causative agent?

Answer 18

Bartonella henselae

Question 19

Bootcamp: Systemic infections
Pt presents with flu-like symptoms, regional lymphadenopathy, and eyrthematous lesion, pain/inflammation and has pets.
How would you diagnose for the causative agent?

Answer 19

• Polymerase chain reaction
• Bx using Warthin-Starry staining to visualize Bartonella henselae

Question 20

Bootcamp: Systemic infections
Pt presents with flu-like symptoms, regional lymphadenopathy, and eyrthematous lesion, pain/inflammation and has pets.
How would you treat against the causative agent?

Answer 20

• Macrolides (azithromycin) for regional infection
• Macrolides (Erythromycin) or Tetracyclines (Doxycycline) for disseminated disease (Liver-peliosis hepatitis) or bacillary angiomatosis, or culture negative endcarditis
• If CNS or Endocarditis is involved, add rifampin to enhance penetrance

Question 21

How do you prevent Rabies from progressing to get symptomatic?

Answer 21

Inactivated vaccine / Killed Vaccine