What laboratory finding is commonly associated with streptococcal pharyngitis?

Streptococcal pharyngitis, commonly known as strep throat, is primarily caused by the bacterium Streptococcus pyogenes, which is a group A beta-hemolytic streptococcus. The presence of gram-positive cocci in chains is a hallmark characteristic when examining samples of this pathogen under a microscope. When a throat swab is taken from a patient with strep throat and subjected to Gram staining, the bacteria will appear as clusters of spherical cells (cocci) grouped together in chains. This presentation aligns with the known morphology of Streptococcus pyogenes and is a critical factor in diagnosing streptococcal infection.

In contrast, other options do not accurately reflect associated laboratory findings for streptococcal pharyngitis. A negative gram stain would not indicate the presence of bacteria, and a positive throat culture for viruses would not be relevant to a bacterial infection like strep throat. Lastly, while elevated white blood cell counts may occur with various infections, eosinophilia is usually associated with allergic reactions or parasitic infections rather than bacterial infections such as streptococcal pharyngitis. Thus, the gram-positive cocci in chains remains the most pertinent laboratory finding for this specific