A 46-year-old man comes to the emergency department due to fever. He returned from a vacation in Southeast Asia a week ago and began having symptoms toward the end of his trip. The patient describes continuous fever that has risen slowly to reach a high plateau and is relieved only by antipyretics. He has also had headaches and abdominal discomfort; he initially had constipation but has had loose stools for the past several days. Temperature is 40 C (104 F), blood pressure is 114/68 mm Hg, and pulse is 62/min. No oropharyngeal lesions, cervical lymphadenopathy, or neck rigidity is present. Lungs are clear on auscultation, and heart sounds are normal. Abdominal examination shows mild distension and generalized tenderness with hepatosplenomegaly. There is a faint, erythematous, macular skin rash over the trunk and abdomen. Laboratory studies reveal mild, normocytic, normochromic anemia and leukopenia with left shift. Peripheral blood smear is normal. Which of the following is the most likely route of transmission of this patient's infection?

Question

A 46-year-old man comes to the emergency department due to fever.  He returned from a vacation in Southeast Asia a week ago and began having symptoms toward the end of his trip.  The patient describes continuous fever that has risen slowly to reach a high plateau and is relieved only by antipyretics.  He has also had headaches and abdominal discomfort; he initially had constipation but has had loose stools for the past several days.  Temperature is 40 C (104 F), blood pressure is 114/68 mm Hg, and pulse is 62/min.  No oropharyngeal lesions, cervical lymphadenopathy, or neck rigidity is present.  Lungs are clear on auscultation, and heart sounds are normal.  Abdominal examination shows mild distension and generalized tenderness with hepatosplenomegaly.  There is a faint, erythematous, macular skin rash over the trunk and abdomen.  Laboratory studies reveal mild, normocytic, normochromic anemia and leukopenia with left shift.  Peripheral blood smear is normal.  Which of the following is the most likely route of transmission of this patient's infection?

Quizplus · Accepted Answer

11ec160b_3856_b316_9249_595f1a43186f_MD0001_00 Typhoid fever is a life-threatening infection caused by Salmonella Typhi or Paratyphi. These gram-negative, enteric pathogens reside only in the gastrointestinal tract of humans (Choice B). Transmission occurs via the fecal-oral route, primarily due to ingestion of food or water contaminated by human feces. Therefore, most cases arise in the developing world where sanitation is poor. Travelers who have not been vaccinated (with typhoid vaccine) are at risk and may return clinically ill. Typhoidal Salmonella species invade enterocytes, travel from the apical to the basolateral end of the cell in vacuoles, and emerge in the intestinal submucosa. Here, the organism is phagocytosed by macrophages but is able to evade destruction due to a specialized capsular antigen (Vi) that impairs the macrophage-mediated oxidative burst. The pathogen subsequently replicates in an unchecked fashion within macrophages and spreads through the lymphatic and reticuloendothelial system, leading to widespread, systemic illness. Manifestations typically develop over weeks in a step-wise fashion. Patients usually develop a progressive fever, often with relative bradycardia (pulse-temperature dissociation), followed by abdominal pain, salmon-colored macules on the trunk ("rose spots"), and constipation or diarrhea. Dissemination through the reticuloendothelial system often causes hepatosplenomegaly, anemia, and leukopenia. Later, ulceration of Peyer patches (lymphoid aggregations in the small intestine submucosa) can result in gastrointestinal bleeding or intestinal perforation. Antibiotic treatment is required to prevent complications and death. (Choice A) Malaria is transmitted by the bite of the female Anopheles mosquito and typically causes paroxysmal fever with nonspecific symptoms (eg, chills, fatigue, headache, myalgias). However, the fever is almost always associated with tachycardia (not bradycardia), and peripheral blood smear will usually demonstrate the parasite and/or signs of red blood cell lysis. (Choice D) Meningococcal meningitis is transmitted by aerosolized droplets from a carrier or infected patient and is associated with rapid-onset confusion, sepsis, hypotension, and a petechial/purpuric rash. (Choice E) Treponema pallidum, the spirochete that causes syphilis, is transmitted sexually. Secondary syphilis is usually characterized by a widespread maculopapular rash that involves the palms and soles, generalized lymphadenopathy, and constitutional symptoms such as fever, headache, and myalgias. This patient's pulse-temperature dissociation, limited rash, and lack of adenopathy make syphilis less likely than typhoid fever. Educational objective: Typhoid fever is caused by Salmonella Typhi or Paratyphi and presents with escalating fever, followed by abdominal pain, formation of rose spots on the chest/abdomen, and hemorrhagic enteritis with possible bowel perforation. Humans are the only reservoir; transmission is fecal-oral and primarily occurs due to ingestion of food or water contaminated with feces.

A 46-Year-Old Man Comes to the Emergency Department Due to Fever