A 4 yr old paially immunized boy came to OPD with history of bouts of coughing. On staining the sputum sample an organism with bipolar staining was seen. Which among the following organism it would be ?
## **Core Concept**
The question tests knowledge of a specific bacterial infection characterized by a distinctive staining pattern in a patient with a history of coughing. The key detail here is the bipolar staining pattern of the organism in the sputum sample. This pattern is classically associated with *Bordetella pertussis*, the causative agent of whooping cough or pertussis.
## **Why the Correct Answer is Right**
The correct answer, *Bordetella pertussis*, is right because it is known for causing pertussis or whooping cough, which presents with bouts of coughing. A hallmark laboratory feature of *B. pertussis* is its appearance on Gram stain, which shows small, Gram-negative coccobacilli with a characteristic bipolar staining, often described as resembling "closed fists" or "eyebrows". This staining pattern is due to the uneven distribution of the bacterial cell's staining material.
## **Why Each Wrong Option is Incorrect**
- **Option A:** *Streptococcus pneumoniae* does not exhibit bipolar staining. It is a Gram-positive diplococcus and is not typically associated with the clinical presentation described.
- **Option B:** *Haemophilus influenzae* is a Gram-negative coccobacillus but does not characteristically show bipolar staining. It can cause respiratory infections but is not specifically identified by this staining pattern.
- **Option D:** *Klebsiella pneumoniae* is a Gram-negative rod that can cause pneumonia but does not exhibit the bipolar staining characteristic of *B. pertussis*.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that *Bordetella pertussis* infections often occur in partially immunized or unimmunized children, presenting with a characteristic "whoop" following bouts of coughing. The diagnosis can be confirmed through PCR or culture, but the distinctive bipolar staining pattern on Gram stain is highly suggestive.
## **Correct Answer:** .