Single most likely diagnosis
- Streptococcus pyogenes: This bacterium is commonly found in chains and is a frequent cause of pharyngitis and skin infections, making it the most likely diagnosis based on the gram stain morphology.
Other Likely diagnoses
- Streptococcus agalactiae (Group B streptococcus): Also forms chains and is a common cause of infections in newborns and pregnant women.
- Streptococcus dysgalactiae: Similar to S. pyogenes and S. agalactiae, it can form chains and cause various infections.
- Enterococcus species: While typically found in pairs, some species can form short chains and are known for their role in urinary tract infections and endocarditis.
Do Not Miss diagnoses
- Streptococcus pneumoniae: Although it typically forms diplococci, some strains can appear in short chains. It's a critical pathogen to identify due to its role in pneumonia, meningitis, and other severe infections.
- Streptococcus milleri group: Includes several species that can form chains and are known for causing abscesses and infections in various body sites.
Rare diagnoses
- Abiotrophia species: Formerly known as nutritionally variant streptococci, they are fastidious and can form chains. They are rare causes of endocarditis and other infections.
- Gemella species: These bacteria can appear as gram-positive cocci in chains and are rarely implicated in human infections, including endocarditis and abscesses.