Most common gram positive cocci responsible for URI in sexually active females.
**Core Concept**
Group A beta-hemolytic Streptococcus (GABHS) and Streptococcus pneumoniae are common causes of upper respiratory infections (URI). However, in sexually active females, a different gram-positive coccus is more commonly implicated.
**Why the Correct Answer is Right**
The correct answer is Group B Streptococcus (GBS). GBS is a gram-positive coccus that frequently colonizes the genitourinary tract. In sexually active females, GBS can cause urinary tract infections (UTIs) and upper respiratory infections. GBS produces hemolysin, which causes beta-hemolysis on blood agar. This organism is also known for causing neonatal sepsis and pneumonia.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Group A beta-hemolytic Streptococcus (GABHS) is more commonly associated with pharyngitis and skin infections, rather than urinary tract infections in sexually active females.
**Option B:** This option is incorrect because Streptococcus pneumoniae is a gram-positive coccus that primarily causes respiratory infections, such as pneumonia and otitis media, rather than urinary tract infections.
**Option C:** This option is incorrect because Enterococcus faecalis is a gram-positive coccus that is commonly associated with urinary tract infections, but it is not the most common cause in sexually active females.
**Clinical Pearl / High-Yield Fact**
GBS can also cause neonatal sepsis and pneumonia, making it an important pathogen to consider in pregnant women and newborns.
**Correct Answer:** D.