Demam Tifoid

01Pathophysiology

Typhoid fever begins with the oral ingestion of Salmonella Typhi, typically through contaminated water or food handled by a chronic carrier. The organism survives gastric acid (aided by a large inoculum or reduced gastric acidity) and reaches the small intestine, where it invades the mucosa overlying Peyer patches in the terminal ileum. This is the single most important anatomic landmark to remember, as it explains both the systemic disease and the feared complications.

Once across the intestinal epithelium, the bacteria are taken up by macrophages. A defining feature of S. Typhi is its ability to survive and replicate within macrophages by evading phagolysosomal killing. The bacteria travel via the lymphatics to the mesenteric lymph nodes, then enter the bloodstream in a primary bacteremia that seeds the reticuloendothelial organs: the liver, spleen, and bone marrow. Multiplication in these organs leads to a secondary bacteremia, which correlates with the onset of sustained high fever and systemic symptoms.

The stepladder fever pattern is explained by this progressive seeding and amplification of bacteremia over the first week. By the second week, fever plateaus at a high sustained level because the bacterial load in the bloodstream and reticuloendothelial system is at its peak.

Rose spots (salmon-colored, blanching maculopapules on the trunk) represent bacterial emboli in the dermal capillaries. Hepatosplenomegaly reflects reticuloendothelial hyperplasia in response to the intracellular infection. Relative bradycardia occurs because S. Typhi produces endotoxin that may alter the cardiac conduction response to fever, so the heart rate fails to rise proportionally with the temperature.

The reason complications such as intestinal hemorrhage and perforation occur in the third week is that Peyer patches undergo hyperplasia, then necrosis, and finally ulceration. These ulcers can erode into blood vessels (hemorrhage) or through the full thickness of the bowel wall (perforation at the terminal ileum). This timeline is heavily tested: vignettes describing a febrile patient who suddenly develops signs of peritonitis in the third week of illness should immediately raise concern for typhoid perforation.

Finally, the chronic carrier state is maintained in the gallbladder, where S. Typhi forms biofilms on gallstones. This explains why chronic carriers are often found to have cholelithiasis, and why cholecystectomy can be curative for the carrier state when antibiotics alone fail.

02Classification and Clinical Manifestation

Typhoid fever progresses through recognizable weekly stages. Though not every patient follows this textbook timeline precisely, exam vignettes rely heavily on it.

Severity classification is clinically relevant for guiding management:

A key point for the exam: in children, diarrhea is more frequent than constipation, which is the opposite of the adult pattern. Vignettes may exploit this distinction.

03Diagnostic Workup

When a vignette describes a traveler returning from an endemic region with stepladder fever and abdominal symptoms, the best initial test is a blood culture. Blood cultures are most sensitive during the first two weeks when bacteremia is at its peak. They should be drawn before antibiotics are started. However, their sensitivity is not perfect (roughly 60% in clinical practice), which is why a negative blood culture does not rule out typhoid.

If blood cultures are negative but clinical suspicion remains high, or if the patient has already received antibiotics, the most accurate confirmatory test is a bone marrow aspirate culture. Bone marrow culture maintains sensitivity of approximately 90% regardless of prior antibiotic use, because the bacterial concentration in the bone marrow is 10-fold higher than in peripheral blood and is less affected by antibiotics. This is the gold standard and is frequently tested.

Stool cultures become positive later in the disease (second to third week) as organisms are shed from the biliary tract back into the intestine. They are more useful for identifying chronic carriers than for acute diagnosis.

The Widal test detects agglutinating antibodies against O (somatic) and H (flagellar) antigens. While historically popular, it is plagued by poor sensitivity and poor positive predictive value, especially in endemic areas where background seropositivity is high. A single Widal test is not reliable. A fourfold rise in titers between acute and convalescent specimens is more meaningful but still inferior to culture-based diagnosis. Exam vignettes that offer the Widal test as the only diagnostic option are typically testing your awareness that it is unreliable.

On the CBC, expect leukopenia or a normal white blood cell count. This is a critical discriminator: most bacterial infections cause leukocytosis, but typhoid characteristically does not. Seeing leukopenia in a febrile patient with abdominal symptoms and travel history should strengthen your suspicion for typhoid rather than lead you toward other bacterial causes.

04Management and Treatment

Acute Stabilization

For any patient presenting with suspected typhoid, the first step is to obtain blood cultures and begin empiric antibiotics. Fluid resuscitation and electrolyte correction are standard supportive measures.

In uncomplicated typhoid where fluoroquinolone susceptibility is confirmed or strongly expected, ciprofloxacin (500 mg PO twice daily for 7 to 14 days) is the treatment of choice due to excellent oral bioavailability and intracellular penetration into macrophages (where the organism resides).

However, fluoroquinolone resistance has become widespread in South and Southeast Asia. For patients with travel history to these regions, azithromycin is now the preferred oral agent for uncomplicated disease. Its advantage is reliable activity against many fluoroquinolone-resistant strains.

For severe typhoid (altered mental status, hemodynamic instability, perforation, or inability to tolerate oral medications), ceftriaxone 2 g IV daily for 10 to 14 days is the drug of choice. Ceftriaxone is also the preferred agent in pregnancy, where fluoroquinolones are contraindicated due to cartilage toxicity in the fetus, and azithromycin data in pregnancy is limited.

Dexamethasone is a tested add-on therapy for typhoid encephalopathy: patients presenting with obtundation, delirium, or shock. The landmark study by Hoffman et al. demonstrated that a high-dose dexamethasone regimen (3 mg/kg loading dose, then 1 mg/kg every 6 hours for 48 hours) significantly reduced mortality in this subset. This is a commonly tested pearl: steroids are not given for all typhoid patients, only for those with severe encephalopathy or shock.

Chronic Carrier Management

Approximately 1 to 5 percent of patients become chronic carriers, defined as continued fecal shedding of S. Typhi for more than 12 months after acute illness. The gallbladder is the reservoir. Prolonged ciprofloxacin (750 mg PO twice daily for 28 days) is the initial approach. If this fails, particularly in the presence of gallstones, cholecystectomy is considered because the biofilm on gallstones cannot be eradicated by antibiotics alone.

Contraindications and Cautions

Next Best Step Logic for Exam Purposes

A vignette describing a febrile traveler from South Asia with the classic presentation: draw blood cultures, then start empiric ceftriaxone if the patient is severely ill, or azithromycin if the case is uncomplicated and South Asian fluoroquinolone resistance is implied. If the vignette says the patient has altered mental status, the next best step after antibiotics is adding dexamethasone.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common trap with typhoid on exams is misinterpreting the white blood cell count. Students see a febrile patient with abdominal pain and assume bacterial peritonitis or another bacterial infection that should produce leukocytosis. Typhoid characteristically shows leukopenia or a normal WBC. If a vignette pairs fever and abdominal symptoms with a notably non-elevated or low white count, that is a strong clue pointing toward typhoid rather than a typical surgical or pyogenic process.

A second trap involves the timing of complications. A question may present a patient in the third week of a febrile illness who suddenly develops severe abdominal pain, rigidity, and free air under the diaphragm. Students may gravitate toward appendicitis or peptic ulcer perforation, but the timeline (third week of sustained fever in a traveler) should lock in typhoid intestinal perforation at the terminal ileum. The perforation site is the terminal ileum, not the duodenum or sigmoid.

Third, do not confuse Salmonella Typhi with non-typhoidal Salmonella. Non-typhoidal Salmonella causes a self-limited gastroenteritis that does not require antibiotics in immunocompetent adults. Typhoid, on the other hand, is a systemic intravascular infection that always requires antibiotics. A vignette that describes bloody diarrhea and food poisoning resolving in a few days is non-typhoidal Salmonella; one that describes prolonged stepladder fever with systemic toxicity is typhoid.

Finally, remember the association between Salmonella osteomyelitis and sickle cell disease. While Staphylococcus aureus is the most common cause of osteomyelitis in the general population, Salmonella species are the most common cause of osteomyelitis in patients with sickle cell disease. If a vignette pairs sickle cell disease with bone pain and fever, consider Salmonella osteomyelitis.

The core competency being tested across typhoid questions is your ability to recognize a constellation of findings (stepladder fever, relative bradycardia, leukopenia, travel history, rose spots), sequence the diagnostic workup correctly (blood culture first, bone marrow culture as gold standard), and select the right antibiotic based on disease severity and resistance patterns.