STREPTOCOCCAL INFECTIONS
Streptococci are classified according to their hemolytic properties (#945;, #946;, #947;) or carbohydrate components in the cell wall (Group A-H, K-V).
Group A #946;-hemolytic streptococci (GA#946;HS) is a common colonizer of oropharynx in normal children (~20%), acquired as droplet infection from infected/ colonized persons.
Pathogenesis: After infection, GA#946;HS attach to oropharyngeal mucosa to produce many extra-cellular toxins, (e.g. pyrogenic exotoxin, streptolysin O and S) for systemic manifestations and digestive enzymes, (e.g. streptokinase, hyaluronidase, DNAse-B) to facilitate the local spread. GA#946;HS disease in children represents: (a) local spread, (b) distant spread via bacteremia, (c) toxin- mediated injury, or (d) immunological injury.
High-risk factors for GA#946;HS infection or colonization include: (a) school-age children, (b) overcrowding, (c) winter season (except by nephritogenic strains, common in summer season).
Clinical spectrum of GA#946;HS disease spans from localized skin/respiratory disease to systemic disease, e.g. rheumatic fever or acute nephritis (Table 10.8).
TABLE 10.8: Clinical spectrum of GA#946;HS infections
Direct spread:
• URTI: Tonsillopharyngitis, otitis, sinusitis
• LRTI: Pneumonia, pleural effusion
• Skin: Impetigo, erysipelas, cellulitis, fasciitis
• Genital: Vulvovaginitis in pre-pubertal girls
Hematogenous spread: (metastatic lesions)
• CNS: Meningitis, brain abscess
• Bones and joints: Arthritis, osteomyelitis
• GIT: Peritonitis, brain abscess
Toxin mediated:
• Scarlet fever
• Streptococcal toxic shock-like syndrome (TSS)
Immunological injury:
• Rheumatic fever
• Acute glomerulonephritis
Diagnosis depends on throat culture in symptomatic case. Positive throat culture in an asymptomatic child is not necessarily pathogenic and reflects colonization.
A serological test-elevated anti-streptolysin O (ASO) titers (gt;200 todd units and rising) is commonly used indicator of recent streptococcal infection. Other serological tests include elevated anti-DNAase B and anti-hyaluronidase titers, which are more specific and anti-streptozyme test, which is most sensitive and detects presence of extracellular streptococcal antigens.Treatment: Penicillin is the drug of choice, given orally or parenterally for minimum 10 days. In allergic individuals, erythromycin, clindamycin or first- generation cephalosporins may be used as alternatives. Prevention: No vaccine is available for clinical use and prophylaxis with long-acting penicillin is recommended only in rheumatic fever.
Scarlet fever, rarely diagnosed in Indian children, is caused by a pyrogenic exotoxin (A, B, C), released by select strains of GA#946;HS.
Clinically, it is characterized by: (a) sudden onset of high fever and sore-throat, (b) typical scarlatiniform rash-a generalized red, punctate exanthem after 24-48 hours of fever that begins from axilla, groin and neck and better felt than visible (goose-flesh or sand-paper skin texture), and (c) circumoral pallor, flushed face and pastia lines (hyperpigmented creases in ante-cubital fossae). Fever subsides spontaneously after 5-7 days, followed by gradual desquamation of rash.
Poststreptococcal reactive arthritis (PSRA) denotes onset of acute arthritis following an episode of GA#946;HS pharyngitis, not fulfilling the Jones criteria for rheumatic fever. It is unclear whether this entity represents a distinct syndrome or a variant of rheumatic fever. Unlike rheumatic fever, PSRA may also involve small peripheral joints and axial skeleton, and is typically non-migratory. ASO titres are elevated.
Response to NSAIDs is usually unsatisfactory. Valvular disease is rare but follow-up is recommended for 1-2 years along with secondary penicillin prophylaxis in some cases.
Pediatric autoimmune neuropsychiatric disorders associated with Streptococcus pyogenes (PANDAS) denotes a group of neuropsychiatric disorders, e.g.
obsessive-compulsive disorder or tics, with a possible relationship with GA#946;HS infection-induced autoimmune antibodies that cross-react with brain tissue. Causal relationship is not yet proven and penicillin prophylaxis or immune-regulatory therapy to treat exacerbations is not recommended.Group B streptococci (GBS) is a normal inhabitant of maternal genital tract and gastrointestinal tract, not associated with any major illness except in newborns. While GBS is the commonest cause of early neonatal sepsis/
meningitis in western countries due to the transvaginal infection during delivery, it is either uncommon or rarely documented in Indian newborns. Penicillin with an aminoglycoside is the drug of choice in these cases.
#945;-hemolytic streptococci, (e.g. S. viridans) is a part of normal skin and oropharyngeal flora. While rarely pathogenic in normal children, it is the commonest cause of infective endocarditis in cases with heart disease. Drug of choice is ampicillin with an aminoglycoside agent.
Group D streptococci, now re-classified as 'Enterococci' (E. faecalis and others), are common inhabitants of oropharynx and gastrointestinal tract. These organisms, previously considered as nonpathogenic, are emerging as important nosocomial pathogens in wound infections, catheter-related sepsis, urinary tract infections and infective endocarditis. Penicillin is generally not effective and drug of choice is ampicillin with an aminoglycoside or vancomycin.
Vancomycin-resistant enterococci (VRE), an emerging problem in recent years, may be treated with linezolid or other newer antibiotics, e.g. daptomycin or tigecycline. Timely removal of urinary and vascular catheters and debridement of necrotic tissue are important strategies to prevent enterococcal infections.
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