Group A Streptococcus (GAS), commonly known as strep, is a highly contagious bacterium responsible for strep throat. While often perceived as a minor illness, untreated GAS infection in adults carries a substantial risk of severe complications. These bacteria can spread directly to nearby tissues or trigger destructive reactions within the body’s immune system. Timely treatment is paramount because the consequences can range from localized abscesses to life-altering systemic diseases affecting the heart and kidneys. Antibiotic intervention is required to prevent both the immediate spread of the bacteria and the development of delayed, long-term conditions.
Acute Localized and Suppurative Complications
Streptococcus pyogenes can spread from the pharynx to adjacent structures, causing localized infections known as suppurative complications. One common complication is a peritonsillar abscess (Quinsy), a collection of pus next to the tonsil. This condition typically causes severe, worsening throat pain, difficulty swallowing, and a change in voice. It often requires surgical drainage in addition to antibiotics.
A retropharyngeal abscess occurs when bacteria spread to the tissues behind the throat. This is dangerous because the swelling may compromise the airway, making breathing difficult. If the infection spreads further into the neck and soft tissues, it can lead to cellulitis, a rapidly spreading bacterial skin infection.
In rare cases, the bacteria can cause invasive Group A Streptococcal disease (iGAS), invading parts of the body that are normally sterile. This includes necrotizing fasciitis (“flesh-eating disease”) or Streptococcal Toxic Shock Syndrome (STSS). These invasive syndromes result from toxins causing widespread tissue damage and organ failure, demanding immediate medical intervention.
The Development of Systemic Autoimmune Sequelae
If a GAS infection is left untreated, it can trigger an immune response where the body’s antibodies mistakenly attack healthy tissues in distant organs. This phenomenon, known as molecular mimicry, is responsible for the most severe systemic complications. The two primary autoimmune sequelae are Acute Rheumatic Fever (ARF) and Post-Streptococcal Glomerulonephritis (PSGN).
Acute Rheumatic Fever typically develops two to four weeks after the initial strep throat infection has resolved. ARF is a generalized inflammatory disorder that can affect the joints, skin, brain, and heart. The inflammation of the joints is often migratory, moving from one large joint to another, causing pain and swelling.
Carditis, the inflammation of the heart tissue, is a significant manifestation of ARF. The immune attack targets the heart valves, leading to scarring and deformation that prevents them from opening or closing properly. This permanent damage is known as Rheumatic Heart Disease (RHD), which can result in chronic heart failure. RHD often requires long-term medication or surgical valve replacement and is a major cause of acquired heart disease globally.
The other major autoimmune complication is Post-Streptococcal Glomerulonephritis (PSGN), which usually appears one to two weeks following a strep infection. PSGN involves inflammation of the glomeruli, the filtering units within the kidneys. This inflammation impairs the kidney’s ability to remove waste and excess fluid from the bloodstream.
Symptoms of PSGN include blood in the urine, reduced urine output, and swelling, particularly around the face and eyes. Unlike ARF, antibiotic treatment of the initial strep infection is not conclusively proven to prevent the development of PSGN. This distinction highlights the unpredictable nature of the autoimmune response triggered by the bacteria.
The Urgency of Diagnosis and Treatment
Timely antibiotic intervention prevents the most serious consequences of a strep infection, particularly Acute Rheumatic Fever (ARF). The window of opportunity is narrow, as treatment remains effective even when started up to nine days after symptom onset. Treating the infection during this period eradicates the GAS bacteria, preventing the destructive autoimmune response.
Accurate diagnosis via a rapid strep test or throat culture is necessary before starting treatment, since antibiotics are ineffective against viral sore throats. Once strep is confirmed, a full course of antibiotics, typically ten days of penicillin or amoxicillin, must be completed. Stopping treatment early risks recurrence and the potential development of sequelae. Completing the regimen ensures the eradication of S. pyogenes, preventing complications and limiting spread.