Infectious Diseases

Topics in this chapter

• Bacterial Infections and Sepsis
• Viral Infections, HIV, and Dengue
• Fungal and Opportunistic Infections
• Respiratory Infectious Diseases
• Neurological and Cardiac Infections
• Gastrointestinal, Skin, and Endocrine Infections
• Sexually Transmitted Infections
• Antimicrobial Therapy and Fluid Management

Practice questions

1. Question 1Q-A356EA

   A 32-year-old male presents with high-grade fever, severe myalgia, retro-orbital pain, and a generalized maculopapular rash. On examination, he has a positive tourniquet test and petechiae on the lower limbs. Laboratory investigations reveal thrombocytopenia (platelet count $45,000/\mu L$) and hemoconcentration with a rising hematocrit. Which of the following is the most appropriate immediate step in the management of this patient?

   1. A.Prophylactic platelet transfusion
   2. B.Cautious intravenous fluid resuscitation with isotonic crystalloids
   3. C.Immediate administration of intravenous broad-spectrum antibiotics
   4. D.High-dose systemic corticosteroids
   See the answer and solution
2. Question 2Q-F59CFA

   A 45-year-old immigrant from Southeast Asia presents to the emergency department with altered mental status, fever, and a generalized petechial rash. He has a history of untreated chronic Hepatitis B. Physical examination reveals hepatosplenomegaly and icterus. Blood cultures grow gram-negative bacilli that are bipolar-staining and exhibit characteristic "safety-pin" appearance on Wayson staining. He reports handling raw fish and seafood recently. Which of the following is the most likely causative organism?

   1. A.Vibrio vulnificus
   2. B.Yersinia pestis
   3. C.Burkholderia pseudomallei
   4. D.Vibrio cholerae
   See the answer and solution
3. Question 3Q-E512E2

   A 28-year-old HIV-positive male with a CD4 count of $45/\mu L$ presents with progressive headache, fever, and lethargy over two weeks. Fundoscopic examination reveals papilledema. Lumbar puncture is performed, and cerebrospinal fluid (CSF) analysis shows an opening pressure of $280\text{ mm } H_2O$, a white cell count of $20/\mu L$ (predominantly lymphocytes), protein of $85\text{ mg/dL}$, and a low glucose of $35\text{ mg/dL}$. Which of the following is the diagnostic test of choice for confirming the most likely etiology?

   1. A.CSF Cryptococcal Antigen lateral flow assay
   2. B.CSF VDRL test
   3. C.CSF PCR for Herpes Simplex Virus
   4. D.Acid-fast bacilli stain of the CSF sediment
   See the answer and solution
4. Question 4Q-8299AC

   A 30-year-old male is evaluated for a painless ulcer on his penis that appeared 3 weeks ago, which has now spontaneously healed. He now presents with a generalized maculopapular rash that involves the palms and soles, along with generalized non-tender lymphadenopathy. Which of the following is the definitive diagnostic method to visualize the causative organism?

   1. A.Gram staining
   2. B.Darkfield microscopy
   3. C.Tzanck smear
   4. D.Culture on Sabouraud agar
   See the answer and solution
5. Question 5Q-9A9002

   A 60-year-old male with type 2 diabetes mellitus is admitted with diabetic ketoacidosis. Over the next 48 hours, he develops acute onset left-sided facial pain, nasal congestion with black necrotic turbinates, and a proptotic left eye with ophthalmoplegia. Biopsy of the nasal mucosa demonstrates broad, non-septate hyphae branching at right angles. Which of the following is the primary pathophysiological mechanism that predisposes this patient to this infection?

   1. A.Neutrophil dysfunction and hyperglycemia creating an acidic environment favoring fungal growth
   2. B.Impaired cell-mediated immunity due to lymphopenia
   3. C.Decreased production of secretory IgA in the mucosal membranes
   4. D.Complement deficiency leading to defective opsonization of encapsulated bacteria
   See the answer and solution