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Streptococcus pyogenes, Molecular Detection

Streptococcus pyogenes is a major human-specific bacterial pathogen that causes a wide array of manifestations ranging from mild localized infections to life-threatening invasive infections. Ineffective treatment of S. pyogenes infections can result in postinfectious sequela acute rheumatic fever and post-streptococcal glomerulonephritis. Moreover, it causes invasive infections like necrotizing fasciitis and toxic shock syndrome that are associated with high morbidity and mortality.

Streptococci are gram-positive, catalase-negative, and coagulase-negative cocci that occur in pairs or chains. They are divided into three groups by the type of hemolysis on blood agar: beta-hemolytic (complete lysis of red cells), alpha-hemolytic (green hemolysis), and gamma-hemolytic (no hemolysis). Beta-hemolytic streptococci are characterized as group A streptococci (Streptococcus pyogenes) and group B streptococci (Streptococcus agalactiae).

S. pyogenes usually colonizes, the pharynx, anus, and genital mucosa. Infections caused by S. pyogenes are highly contagious. Transmission can occur through airborne droplets, hand contact with nasal discharge or with objects or surfaces contaminated with bacteria, skin contact with contaminated lesions, or contaminated food sources.

Sore throat is usually a major complaint in the case of streptococcus pharyngitis. The most common clinical findings for Streptococcal pharyngitis include sudden onset of fever, malaise, pharyngeal exudate, tender cervical lymphadenopathy, and enlarged tonsils.

In children, impetigo is one of the most common skin infections. Typically, the itchy reddish rash appears around the mouth or nose that becomes a fluid-filled blister later. Blisters rupture easily and are covered with honey-colored crust. The lesions are usually well-localized and affect exposed areas of the body: the face and lower extremities. There are typically no systemic manifestations of impetigo.

Patients with scarlet fever usually present with high-grade fever, sore throat, strawberry-like tongue, and a papular, non-confluent rash. The rash typically lasts for 7 to 10 weeks, follows by desquamation. Desquamation can only be observed on the palms and soles.

Soft tissue invasive infections due to S. pyogenes mostly present with shock and multiorgan failure.

Necrotizing fasciitis due to group A streptococcus (S. pyogenes) is a deep-seated infection of the subcutaneous tissue that causes rapid destruction of fascia and fat. Immunocompromised individuals are at increased risk for developing necrotizing fasciitis. Other risk factors include surgical procedures, burns, blunt trauma, and childbirth. Localized pain, necrosis of the infected skin lesion, swelling, redness, increased heart rate, and fever are the typical manifestations of necrotizing fasciitis. In the advanced stage of the disease, a picture of septic shock can be present.

Complications of S. pyogenes infections can be divided into suppurative and non-suppurative complications.

Suppurative complications include peritonsillar abscess, peritonsillar cellulitis, retropharyngeal abscess, otitis media and sinusitis, uvulitis, cervical lymphadenitis, meningitis, brain abscess, arthritis, endocarditis, osteomyelitis, and liver abscess.

Non-suppurative complications are rheumatic fever, post-streptococcal glomerulonephritis, PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections), Sydenham chorea, and other autoimmune movement disorders.

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