In a case of neonatal meningitis, the etiologic bacteria was found to have properties of β hemolysis, bacitracin resistance, CAMP positive. Which of the following is most likely causative agent?
## **Core Concept**
The question pertains to the identification of a bacterial pathogen causing neonatal meningitis, based on specific laboratory characteristics. The bacteria in question exhibits β hemolysis, resistance to bacitracin, and a positive CAMP test. These properties are critical for differentiating among certain Gram-positive cocci.
## **Why the Correct Answer is Right**
The bacteria described matches *Streptococcus agalactiae*, also known as Group B Streptococcus (GBS). Key characteristics of GBS include:
- **β hemolysis**: This indicates the bacteria can completely lyse red blood cells in agar, appearing transparent with a clear zone around colonies.
- **Bacitracin resistance**: Unlike *Streptococcus pyogenes* (Group A beta-hemolytic streptococci), which is sensitive to bacitracin, GBS is resistant.
- **CAMP test positive**: The CAMP (Christie–Atkins–Munch-Petersen) test is used to identify GBS. A positive test shows an enhanced hemolysis pattern when GBS is streaked perpendicular to *Staphylococcus aureus* on blood agar, due to the synergistic effect of GBS' hemolysin and *S. aureus*' alpha-toxin.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, incorrect options might include other bacteria that do not match all the given characteristics.
- **Option B:** If this option were *Streptococcus pyogenes* (Group A streptococcus), it would be bacitracin sensitive, not resistant.
- **Option C:** If this option were *Enterococcus*, it would not exhibit a positive CAMP test or β hemolysis to the extent described for GBS.
- **Option D:** Without specifics, assuming another streptococcal species, it likely wouldn't match all three criteria (β hemolysis, bacitracin resistance, CAMP positive).
## **Clinical Pearl / High-Yield Fact**
A critical point to remember is that Group B Streptococcus (GBS) is a leading cause of neonatal sepsis and meningitis. Pregnant women are often screened for GBS colonization between 35-37 weeks of gestation, and those positive may receive intrapartum antibiotic prophylaxis to reduce the risk of neonatal infection.
## **Correct Answer:** .