Can a diagnosis be made for a patient with chest pain, fever, and abnormal bowel movements, who has leukocytosis with neutrophilia, and has been given paracetamol, with negative tests for Salmonella and Dengue?

Diagnosis: Invasive Bacterial Enterocolitis with Systemic Inflammatory Response

This patient requires immediate empirical antibiotic therapy for presumed invasive bacterial enterocolitis, as the combination of fever, gastrointestinal symptoms (hard followed by loose stool), and leukocytosis (WBC 14,000) with marked neutrophilia (85%) strongly indicates bacterial infection rather than viral or parasitic etiology. 1, 2

Critical Laboratory Interpretation

The laboratory findings are highly suggestive of invasive bacterial pathogen:

• Leukocytosis with neutrophilia (WBC 14,000 with 85% neutrophils) indicates bacterial infection, as the total white blood cell count and neutrophil count are often increased with invasive bacterial pathogens 1
• Anemia (Hgb 104 g/L) may suggest dehydration or early hemolysis, requiring close monitoring 1
• Negative Salmonella and Dengue serology helps exclude these specific pathogens but does not rule out other invasive bacterial causes 1, 3

The combination of neutrophilia and gastrointestinal symptoms strongly suggests invasive bacterial pathogens such as Shigella, Campylobacter, Yersinia, or non-typhoidal Salmonella rather than viral or parasitic etiology 1, 2

Immediate Diagnostic Workup Required

Obtain the following tests urgently before starting antibiotics:

• Stool culture for Salmonella, Shigella, Campylobacter, Yersinia, and E. coli (including STEC with Shiga toxin testing) 1, 3
• Stool examination for fecal leukocytes and occult blood to confirm invasive bacterial enterocolitis 1, 2
• Blood cultures given fever and systemic manifestations 3
• Abdominal CT scan with IV contrast to evaluate for bowel wall thickening, perforation, or abscess formation 2

Empirical Antibiotic Therapy

Start empirical antibiotics immediately after obtaining specimens:

• First-line regimen: Ciprofloxacin or azithromycin for presumed bacillary dysentery 2, 3
• Alternative for severe disease: Piperacillin-tazobactam, imipenem-cilastatin, or meropenem if neutropenic enterocolitis or sepsis is suspected 2
• Duration: Continue IV antibiotics for 7-10 days, adjusting based on culture results and clinical improvement 2

The Infectious Diseases Society of America recommends empirical antibiotics before culture results in patients with fever AND bloody/mucoid diarrhea, severe systemic symptoms, or signs of sepsis 3

Critical Monitoring Parameters

Monitor closely for complications:

• Hemolytic uremic syndrome (HUS): Check hemoglobin and platelet counts daily for 14 days if STEC is identified, as high WBC and neutrophil counts often occur in patients who subsequently develop HUS 1
• Septic shock: Monitor vital signs, urine output, and mental status 1
• Surgical complications: Obtain surgical consultation if signs of peritonitis, bowel wall thickening >10mm, perforation, or clinical deterioration develop 2

Important Clinical Pitfalls

Common diagnostic errors to avoid:

• Do not rely on serologic tests (Widal test) for diagnosis of enteric fever due to poor performance characteristics 1
• Do not withhold antibiotics if STEC is suspected, as this requires supportive care ONLY without antibiotics 3
• Consider concurrent bacteremia in patients with prolonged fever (>5 days), as dengue-negative patients with persistent fever and leukocytosis may have secondary bacterial infections 4, 5
• The chest pain warrants evaluation for extravascular foci of infection, particularly if fever persists despite adequate antimicrobial therapy 1

Pathogen-Specific Adjustments

Once culture results are available:

• If Shigella identified: Always treat with antibiotics to reduce duration and shedding 3
• If non-typhoidal Salmonella identified: Treat only if age <6 months, immunocompromised, or signs of systemic spread 3
• If STEC identified: Stop antibiotics immediately and provide supportive care only, with close monitoring for HUS 3