Strep throat

Overview

Strep throat, also known as streptococcal pharyngitis, is an acute infection of the throat and tonsils caused by the bacterium Group A Streptococcus (GAS). It is a common condition, especially among children and adolescents, characterized by a sudden onset of sore throat, fever, and swollen lymph nodes. Unlike viral sore throats, strep throat requires antibiotic treatment to prevent complications such as rheumatic fever and kidney inflammation.

Etiology

Strep throat is primarily caused by Group A Streptococcus, a gram-positive bacterium that is highly contagious. The bacteria spread through respiratory droplets when an infected person coughs or sneezes. It can also be transmitted via direct contact with contaminated surfaces or objects. Although less common, strep throat can also be caused by other streptococcal groups, such as Group C and Group G.

Pathophysiology

Upon entering the body, the bacteria adhere to the epithelial cells of the pharynx using specific virulence factors, such as M protein and lipoteichoic acid. These factors facilitate colonization and invasion of the host tissues. The immune response to the infection involves the activation of both humoral and cellular immunity, leading to inflammation and the characteristic symptoms of strep throat.

Clinical Manifestations

The symptoms of strep throat typically appear 2 to 5 days after exposure to the bacteria. Common clinical features include:

Sudden onset of sore throat
Painful swallowing
Fever, often exceeding 38°C (100.4°F)
Red and swollen tonsils, sometimes with white patches or streaks of pus
Swollen and tender cervical lymph nodes
Headache
Nausea and vomiting, particularly in children
Absence of cough, which helps differentiate it from viral pharyngitis

Diagnosis

The diagnosis of strep throat is primarily clinical, supported by laboratory tests. A rapid antigen detection test (RADT) can quickly confirm the presence of Group A Streptococcus. If the RADT is negative but clinical suspicion remains high, a throat culture is recommended for definitive diagnosis. The Centor criteria, which include fever, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough, can aid in the clinical assessment.

Treatment

Antibiotic therapy is the cornerstone of treatment for strep throat. Penicillin or amoxicillin is typically the first-line treatment due to their efficacy and narrow spectrum. For patients allergic to penicillin, alternatives such as cephalexin, clindamycin, or azithromycin may be used. Antibiotic treatment not only alleviates symptoms but also reduces the risk of complications and transmission.

Complications

If left untreated, strep throat can lead to several complications, including:

Rheumatic fever, an inflammatory disease that can affect the heart, joints, skin, and brain
Post-streptococcal glomerulonephritis, a kidney condition
Peritonsillar abscess, a collection of pus near the tonsils
Scarlet fever, characterized by a red rash
Otitis media and sinusitis

Prevention

Preventive measures for strep throat focus on reducing transmission. These include:

Practicing good hand hygiene
Avoiding close contact with infected individuals
Covering mouth and nose when coughing or sneezing
Regular cleaning of surfaces and objects

Epidemiology

Strep throat is most prevalent among children aged 5 to 15 years, although it can occur at any age. It is more common in late fall, winter, and early spring. Outbreaks are frequent in crowded settings such as schools and daycare centers.

Prognosis

With appropriate antibiotic treatment, the prognosis for strep throat is excellent. Symptoms typically improve within 1 to 3 days of starting antibiotics, and complications are rare. However, untreated strep throat can lead to serious sequelae, underscoring the importance of timely diagnosis and management.