Update in Pediatrics 2018th Edition Ebook PDF download
Update in Pediatrics 2018th Edition Ebook PDF download n the evaluation of a patient with sore throat, the primary concern in the United States is usually accurate diagnosis and treatment of pharyngitis caused by group A streptococci (GAS) or Streptococcus pyogenes, which accounts for about 15% of all episodes of pharyngitis. The sequelae of GAS pharyngitis, especially acute rheumatic fever (ARF) and acute glomerulonephritis (AGN), at one time resulted in considerable morbidity and mortality in the United States and continue to do so in other parts of the world. Prevention of ARF in particular depends on timely diagnosis of streptococcal pharyngitis and prompt antibiotic treatment.
Group A streptococci are characterized by the presence of group A carbohydrate in the cell wall, and they are further distinguished by several cell wall protein antigens (M, R, T). These protein antigens, especially the M protein, a virulence factor, are useful for studies of epidemiology and pathogenesis but are not used in clinical care.
GAS pharyngitis is endemic in the United States; epidemics occur sporadically. Episodes peak in the late winter and early spring. Rates of GAS pharyngitis are highest among children aged 5-11 years old.
Spread of GAS in classrooms and among family members is common, especially in the presence of crowded living conditions.
Transmission occurs primarily by the inhalation of organisms in large droplets or by direct contact with respiratory secretions. Pets do not appear to be a frequent reservoir. Untreated streptococcal pharyngitis is particularly contagious early in the acute illness and for the first 2 weeks after the organism has been acquired, but antibiotic therapy effectively prevents disease transmission. Within 24 hours of institution of therapy with penicillin, it is difficult to isolate GAS from patients with acute streptococcal pharyngitis, and infected children can return to school.
Molecular epidemiology studies of streptococcal pharyngitis have shown that the prevalent M protein types vary among communities and over time.
Numerous distinct strains of GAS can circulate simultaneously in a community during the peak season. GAS M proteins can be identified in research studies by using PCR to establish the specific M protein gene (emm gene); M protein identification is not available for use in clinical care. Children with streptococcal pharyngitis can serve as a local reservoir for strains that cause invasive disease (e.g., sepsis, streptococcal toxic shock syndrome, cellulitis, necrotizing fasciitis) in the same geographic area and season.