Strep is a colloquial term for bacterial infections caused by streptococci, particularly group A Streptococcus pyogenes, and is most often used to refer to streptococcal pharyngitis (“strep throat”).
Explanation
The genus Streptococcus comprises many species of Gram‑positive, catalase‑negative cocci that arrange in chains or pairs. When people talk about “strep,” they are usually referring to group A beta‑hemolytic streptococci. Streptococcus pyogenes colonizes the throat and skin and causes pharyngitis, tonsillitis, impetigo, scarlet fever and invasive conditions such as necrotizing fasciitis and streptococcal toxic shock syndrome. Untreated infections can lead to immunologic sequelae like rheumatic fever and post‑streptococcal glomerulonephritis. Group B streptococci (Streptococcus agalactiae) are another important group, colonizing the genital and gastrointestinal tracts and causing neonatal sepsis and meningitis. Viridans streptococci inhabit the oral cavity and can enter the bloodstream during dental procedures, resulting in subacute endocarditis in susceptible individuals. Diagnosis of streptococcal infections often involves rapid antigen detection tests (“rapid strep tests”) or culture of throat swabs on blood agar to detect beta hemolysis. Prompt treatment with appropriate antibiotics, typically penicillin or amoxicillin, eradicates the bacteria and prevents complications.
Common uses and examples
“Strep throat” refers to acute tonsillopharyngitis caused by group A strep, characterized by sore throat, fever, pharyngeal exudate and tender cervical lymph nodes. A rapid strep test performed in a doctor’s office can confirm the diagnosis in minutes. “Strep skin infection” may refer to streptococcal impetigo or cellulitis. Pregnant women are screened for group B strep colonization to reduce the risk of transmitting the organism to the newborn during delivery; intrapartum antibiotic prophylaxis is given when indicated. Group C and group G streptococci can cause pharyngitis and bacteremia but are less common. The term “strep pneumonia” may be used colloquially for pneumococcal pneumonia caused by Streptococcus pneumoniae, an alpha‑hemolytic species.
Because “strep” encompasses several species and disease presentations, context is important when interpreting the term. Understanding which streptococcal group is involved guides diagnosis, therapy and prevention strategies.
Related Terms: Streptococcus, Streptococcus pyogenes, Streptococcal pharyngitis, Rapid strep test, Beta-hemolysis