Group A Streptococcus (GAS) is the bacteria responsible for strep throat, a common cause of pharyngitis, particularly in children and adolescents. This infection typically presents with a sudden onset of symptoms, including a sore throat, fever, and often redness or white patches on the tonsils. Swollen lymph nodes in the neck are also frequent, sometimes accompanied by headache or stomach pain, especially in younger patients. While many sore throats are caused by viruses, strep throat carries the potential for severe health consequences if left untreated.
Prolonged Illness and Local Infections
If a person does not take antibiotics for a confirmed Group A Strep infection, acute symptoms will be prolonged and more severe. Although the body’s immune system may eventually clear the bacteria, the illness duration can extend significantly, leading to a longer period of high fever and severe throat pain. This extended infection time also increases the risk of the bacteria spreading to adjacent tissues, causing localized, pus-forming complications known as suppurative sequelae.
One concerning local complication is a peritonsillar abscess, sometimes called quinsy, a collection of pus surrounding the tonsil. This abscess can cause severe, usually one-sided, throat pain, difficulty opening the mouth, and muffled speech, often requiring surgical drainage in addition to antibiotics. The infection can also extend into the middle ear (otitis media) or into the sinuses (sinusitis). In rare instances, the infection can spread into the deeper structures of the neck, potentially leading to airway obstruction or pneumonia if the abscess ruptures.
The Danger of Rheumatic Fever
Antibiotics are prescribed primarily to prevent Acute Rheumatic Fever (ARF), a serious, delayed complication. ARF is not caused directly by the bacteria, but is instead an autoimmune condition that develops approximately two to four weeks after the initial infection. It is classified as a non-suppurative sequela, resulting from a misdirected immune response rather than the direct spread of bacteria.
This autoimmune reaction is driven by molecular mimicry, where antibodies produced to fight Streptococcus mistakenly attack similar proteins in the host’s own tissues. The major tissues affected by this cross-reaction are the heart, joints, brain, and skin. The most damaging manifestation is carditis, inflammation of the heart muscle and valves, often leading to permanent Rheumatic Heart Disease (RHD).
RHD can result in scarred, malfunctioning heart valves that permanently affect heart function. Other significant manifestations of ARF include migratory arthritis, painful joint swelling that moves between joints without causing permanent damage, and Sydenham’s chorea, a neurological disorder characterized by involuntary, jerky movements. The risk of developing ARF is dramatically reduced if antibiotic treatment is started within nine days of symptom onset.
Post-Streptococcal Kidney and Neurological Issues
Another systemic complication following untreated strep infection is Post-streptococcal Glomerulonephritis (PSGN). This condition involves inflammation of the glomeruli, the tiny filtering units within the kidneys. PSGN typically develops one to two weeks after a strep throat infection.
The inflammation in PSGN occurs when immune complexes (antibodies bound to streptococcal antigens) become trapped in the kidney filters. This trapping damages the filters, leading to symptoms like blood in the urine (hematuria), which may appear dark or rusty, and swelling (edema), particularly around the eyes and face. While most children recover fully from PSGN, it can lead to high blood pressure and, in rare instances, acute or chronic kidney failure.
Another condition linked to Group A Strep infections is Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS). PANDAS is characterized by the sudden onset or worsening of obsessive-compulsive disorder (OCD) or tic disorders following a strep infection. Similar to ARF, the underlying theory involves an autoimmune mechanism where antibodies mistakenly target the basal ganglia region of the brain. Treating the underlying strep infection remains a component of the management strategy, although the relationship is complex and still under investigation.
The Primary Role of Antibiotic Therapy
Antibiotics for strep throat serve a dual purpose: shortening the duration of acute illness and preventing serious, delayed sequelae. Penicillin and amoxicillin are the most commonly prescribed antibiotics and are highly effective against Streptococcus. Preventing ARF and PSGN is the primary medical justification for treatment.
Antibiotic treatment, which typically lasts for ten days, must be completed even if symptoms resolve quickly, usually within one to two days. Stopping the medication early allows remaining bacteria to potentially trigger the harmful immune response that causes rheumatic fever and other complications. A definitive diagnosis, usually via a rapid strep test or throat culture, is necessary before treatment to confirm the infection is bacterial and avoid unnecessary antibiotic use.