Dr. Raj Kumar Kayal*
Sr. Pediatrician, Guwahati *
|Streptococci are gram positive, non-motile bacteria, 0.6-1.0 micrometer in diameter, forming chains in liquid media. They are common human pathogens, but also form part of the normal flora of the respiratory, gastrointestinal, and genitourinary flora. The B-hemolytic streptococci are characterized by a zone of complete hemolysis around their colonies on blood agar plates. They are further subdivided on the basis of a group specific polysaccharide present in their cell wall into groups designated A through V. Group A Streptococci are again divided into > 100 serotypes, on the basis of their M protein antigen. Some serotypes cause pharyngitis, whereas others cause skin and soft tissue infections and many serotypes cause both.
The cell wall contains a carbohydrate antigen, the M protein, and a polysaccharide capsule made of hyaluronic acid. The organism produces many extra cellular products which play an important role in local and systemic toxicity and in spread of the infection through various tissues. These include Streptolysin Sand 0, DNAse, protease and pyrogenic exotoxins A, Band C. These exotoxins produce the rash of Scarlet fever and may be responsible for severe illness including Streptococcal toxic shock syndrome, by acting as super antigens. Antibodies against many of these products are measured for serodiagnosis.
Streptococci cause a variety of illnesses in humans e.g., pharyngitis, skin and soft tissue infections, pneumonia, septicemia, arthritis or osteomyelitis, meningitis, scarlet fever, toxic shock syndrome etc. They also cause some non-suppurative illnesses like rheumatic fever, glomerulonephritis etc.
It occurs mostly in children above three years of age. There is fever, malaise, sore throat, sometimes pain abdomen, and vomiting. Throat examination may reveal mild to intense erythema, purulent exudates over the tonsils or posterior pharyngeal wall along with tender cervical lymphadenopathy. Group A Streptococci account for only up to 15 percent of all cases of sore throat. Throat swab culture is the "gold standard" of diagnosis but in western countries, a rapid antigen test, if positive obviates the need for culture. Antibody titres are used, not to diagnose current infection but to document recent streptococcal infection in suspected cases of rheumatic fever etc. Streptococcal pharyngitis is usually self-limiting and resolves within 3-5 days even without therapy. Rarely, it may spread locally to cause retropharyngeal or parapharyngeal abscess or cause distant disease. Antibiotics prevent this spread, cut short the average duration of the illness by around one day, and most important, prevent acute rheumatic fever, if started within 9 days of onset of the illness. Acute post-streptococcal glomerulonephritis, however may not be thus preventable.
It is clinically like streptococcal sore throat along with a typical rash, occurring within 24-48 hours of the onset of the illness. The rash is erythematous, diffuse and sandpapery, visible more on flexor skin creases, skipping the circumoral area and it blanches on pressure. It starts to fade after 3-4 days and there may be desquamation in the palms, soles and fingers. The tongue is initially coated and later becomes strawberry-like.
Streptococcus is a common cause of non-bullous impetigo, along with Staphylococcus aureus. It is an infection of the superficial layers of the skin and presents as small, usually multiple, discrete papulovesicular lesions which soon become crusted and may spread locally or to other parts of the body. The face and limbs are the usual sites. Regional lymphadenopathy is common and systemic features are absent.
It is an infection of the deeper skin layers and underlying connective tissue. The affected skin becomes red, hot and tender with sharply defined margins. Blebs may be present. Systemic features like fever are present.
It may occur in prepubertal girls and is manifested by discomfort and pain during micturition and even walking. There may be local erythema and a serous discharge. Sexual abuse needs to be ruled out in such cases.
In this condition there is perianal erythema with well-defined margins and there is itching and painful defection, often with blood-tinged stools. Response to antibiotics is prompt and gratifying.
This condition has been recognized in last two decades as an important manifestation of severe streptococcal disease. There is rapidly progressing infection and destruction of the skin and underlying soft tissue. It is also known as streptococcal gangrene. The child is very sick and needs aggressive resuscitation, parenteral antibiotics, and early surgical debridement of necrotic tissue. Chickenpox is a common predisposing condition.
Streptococcal Toxic Shock Syndrome
Some strains of Group A streptococci produce exotoxins A, B, C and some other toxins which act as superantigens and cause release of massive amounts of proinflammatory cytokines in the host. The syndrome is diagnosed in the presence of hypotension or shock plus at least two of the following six criteria: renal impairment, coagulopathy, hepatic abnormalities, generalized scarlatiniform rash, acute respiratory distress syndrome, and soft tissue necrosis. These disorders must not be due to some other explanation and there should be isolation of Group A Streptococci from a normally sterile body site.
Other invasive streptococcal infections
Group A streptococci also cause many common infections e.g., bacteremia without focus, pneumonia, meningitis, osteomyelitis, pyogenic arthritis, puerperal sepsis, surgical wound infection, myositis, peritonitis etc.
Acute Rheumatic Fever
Because this organism shares certain common antigens with human tissues, it can cause some well recognized nonsuppurative complications also. Rheumatic fever is the leading cause of acquired heart disease in children in developing countries. It occurs 2-4 weeks after a streptococcal pharyngitis. Duckett Jones in 1944 had devised the diagnostic criteria of ARF which are still followed, albeit with some revision.
PSGN follows infections of the throat or skin with nephritogenic strains of streptococci and is a common cause of acute renal disease in children. In contrast to ARF, there is no recurrence of PSGN after recurrent streptococcal infections.
Streptococcal Reactive Arthritis
Many children develop an illness after GAS infection which does not fulfill the revised Jones' criteria for ARF. Their disease may involve smaller joints, as also the axial skeleton and the arthritis may be additive rather than migratory. Aspirin does not give as dramatic relief as in classical ARF. The interval between sore throat and onset of illness is usually less than 10 days here. Carditis may develop in some cases. Some authors recommend one year antibiotic prophylaxis in all cases, but prophylaxis as for ARF is mandatory if carditis develops.
Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus pyogenes
PANDAS is a relatively recent entity. The child presents with tics, obsessive-compulsive behavior and Tourette syndrome and there is evidence of recent streptococcal infection in many cases, along with anti basal ganglia antibodies. The treatment of this condition, as well as its very existence is subject of intense debate.
- Gerber MA. In: Kliegman RM. Behrman RE, Jenson HB, Stanton FB, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia. Saunders. 2007. 1135-1140.
- Wessels MR. In Kasper DL, Fauci AS, Longo DL, Braunwald E, et al, eds. Harrison's Principles of Internal. Medicine. 16th ed. New York. McGraw Hill. 2005. 823-831.
- Jaggi P, Shulman ST. Group A Streptococcal Infections. Pediatrics in Review 2006;27.99-105.
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|Kayal K R D.. Available From : http://www.pediatriconcall.com/fordoctor/ Conference_abstracts/report.aspx?reportid=50|