Which bacterium is typically detected by rapid strep testing in pharyngitis?

Which bacterium is typically detected by rapid strep testing in pharyngitis?

• A. Streptococcus pneumoniae
• B. Haemophilus influenzae
• C. Neisseria gonorrhoeae
• D. Streptococcus pyogenes

Answer: (D)

The main idea is that rapid strep testing for pharyngitis is specifically designed to detect Streptococcus pyogenes, the group A streptococcus that causes classic strep throat. These rapid antigen tests look for the group A carbohydrate on the surface of the bacteria, so a positive result confirms infection with S. pyogenes and supports antibiotic treatment to shorten symptoms and reduce the risk of complications like rheumatic fever. It does not detect the other bacteria listed, which are associated with different illnesses and are identified with other tests. Streptococcus pneumoniae is a common cause of pneumonia, sinusitis, and meningitis, not typical strep pharyngitis; Haemophilus influenzae likewise causes illnesses such as otitis media, sinusitis, or epiglottitis and requires other testing; Neisseria gonorrhoeae causes gonorrheal pharyngitis and is diagnosed with nucleic acid amplification tests specific for GC/CT rather than a rapid strep assay. Because rapid tests aren’t perfect, a negative result in someone with high clinical suspicion—especially children—may prompt a throat culture or a more sensitive NAAT to rule out strep.

The main idea is that rapid strep testing for pharyngitis is specifically designed to detect Streptococcus pyogenes, the group A streptococcus that causes classic strep throat. These rapid antigen tests look for the group A carbohydrate on the surface of the bacteria, so a positive result confirms infection with S. pyogenes and supports antibiotic treatment to shorten symptoms and reduce the risk of complications like rheumatic fever. It does not detect the other bacteria listed, which are associated with different illnesses and are identified with other tests. Streptococcus pneumoniae is a common cause of pneumonia, sinusitis, and meningitis, not typical strep pharyngitis; Haemophilus influenzae likewise causes illnesses such as otitis media, sinusitis, or epiglottitis and requires other testing; Neisseria gonorrhoeae causes gonorrheal pharyngitis and is diagnosed with nucleic acid amplification tests specific for GC/CT rather than a rapid strep assay. Because rapid tests aren’t perfect, a negative result in someone with high clinical suspicion—especially children—may prompt a throat culture or a more sensitive NAAT to rule out strep.