A child presents with sepsis. Bacteria isolated showed beta-hemolysis on blood agar, resistance to bacitracin, and a positive CAMP test. The most probable organism causing infection is
**Core Concept**
The child's clinical presentation of sepsis and the laboratory findings suggest an infection caused by a specific type of bacteria that exhibits beta-hemolysis, resistance to bacitracin, and a positive CAMP test. These characteristics are indicative of a particular bacterial species that is commonly associated with invasive infections.
**Why the Correct Answer is Right**
The organism in question is likely *Streptococcus agalactiae*, also known as Group B Streptococcus (GBS). The beta-hemolysis on blood agar is due to the production of hemolysin, which breaks down red blood cells. The resistance to bacitracin is a key identifying feature of GBS, as it is sensitive to this antibiotic. The positive CAMP test is also characteristic of GBS, as it produces an enzyme that enhances the hemolysis produced by *Staphylococcus aureus*, resulting in a characteristic double zone of hemolysis.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not match the laboratory findings of beta-hemolysis, resistance to bacitracin, and a positive CAMP test.
* **Option B:** This option is incorrect because it does not align with the clinical presentation of sepsis and the specific laboratory characteristics mentioned.
* **Option C:** This option is incorrect because it does not match the laboratory findings of beta-hemolysis, resistance to bacitracin, and a positive CAMP test.
**Clinical Pearl / High-Yield Fact**
GBS is a leading cause of invasive neonatal infections, including sepsis, pneumonia, and meningitis. It is also a common cause of illness in pregnant women and older adults. The CAMP test is a rapid and simple method for identifying GBS from clinical specimens.
**Correct Answer: D. Streptococcus agalactiae**