A 50 year old chronic alcoholic male agricultural worker presented with high grade fever of one week duration with spells of chills and rigor. Examination of the respiratory system revealed bilateral crepitations with scattered rhonchi. Multiple subcutaneous nodules were found on the extensor surface of the left forearm, arm and left leg. Direct microscopy of the pus aspirated from the skin nodule revealed plenty of Gram negative bacilli with bipolar staining. Culture revealed distinct rough corrugated grey-white colonies on Blood agar. The organisms were motile and oxidase positive. The most likely diagnosis is –
A 50 year old chronic alcoholic male agricultural worker presented with high grade fever of one week duration with spells of chills and rigor. Examination of the respiratory system revealed bilateral crepitations with scattered rhonchi. Multiple subcutaneous nodules were found on the extensor surface of the left forearm, arm and left leg. Direct microscopy of the pus aspirated from the skin nodule revealed plenty of Gram negative bacilli with bipolar staining. Culture revealed distinct rough corrugated grey-white colonies on Blood agar. The organisms were motile and oxidase positive. The most likely diagnosis is –
💡 Explanation
## **Core Concept**
The question describes a clinical scenario suggestive of a specific bacterial infection, characterized by high-grade fever, chills, respiratory symptoms, and subcutaneous nodules. The diagnosis is based on the microbiological findings of Gram-negative bacilli with bipolar staining, distinct colony morphology on Blood agar, and specific biochemical properties.
## **Why the Correct Answer is Right**
The clinical presentation of high-grade fever, chills, bilateral crepitations, and subcutaneous nodules, along with the patient's history of chronic alcoholism and occupational exposure, points towards a diagnosis of melioidosis. The microbiological findings of Gram-negative bacilli with bipolar staining (safety pin appearance), rough corrugated colonies on Blood agar, and the organisms being motile and oxidase-positive are characteristic of *Burkholderia pseudomallei*. This bacterium is known to cause melioidosis, a disease that can present with a variety of clinical manifestations, including skin and soft tissue infections, pneumonia, and sepsis.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although it might represent a Gram-negative infection, the specific microbiological characteristics mentioned do not match *Burkholderia pseudomallei*.
- **Option B:** This option is incorrect as it does not align with the described microbiological features of the causative organism in this case.
- **Option D:** This option is incorrect because the clinical and microbiological features do not align with the typical presentation and laboratory findings of the disease caused by this organism.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that melioidosis, caused by *Burkholderia pseudomallei*, is a disease that can mimic other conditions, such as tuberculosis or pyogenic infections, but the presence of characteristic bipolar staining (safety pin appearance) on microscopy and specific colony morphology on Blood agar are diagnostic clues.