The Dynamics of Streptococcal Infections in a Defined Population of Children: Serotypes Associated With Skin and Respiratory Infections1

Abstract

Serial observations including cultures of the upper respiratory tract and of infected skin lesions and streptococcal antibody determinations were made over a two-year period in a semi-closed population of children between 10 months and 15 years of age. There was a high prevalence of group A streptococci in nose and throat cultures and of skin lesions containing these organisms. Almost 90% of the study population developed streptococcal impetigo during the study period. A slightly higher proportion of males than females developed skin infection but there was no relationship to age. Impetigo was observed throughout the calendar year, exceeding 12% of child-visits in one winter month, but was generally more common in the summer and fall. Conversely, group A streptococci were more often isolated from nose and throat cultures in the winter months. The increase in recovery of streptococci from nose and throat cultures lagged behind the increase in streptococcal impetigo and continued into the winter months, when the prevalence of impetigo had declined. Calculation of ratios for individual streptococcal serotypes isolated from different body sites revealed a clear cut distinction between "respiratory" and "impetigo" serotypes, with respect to both prevalence and acquisition rates. Respiratory serotypes were more commonly isolated in the winter and impetigo serotypes in the summer and fall. Significant antibody responses to extracellular antigens of the streptococcus were documented for pharyngeal acquisitions of both impetigo and respiratory serotypes and for skin lesions associated with impetigo serotypes. Group A streptococcal serotypes may be divided into three categories on the basis of their human pathogenicity for body sites: some with the potential for respiratory infection, others with the potential for skin infection and a few unusual serotypes with the potential for infecting both sites.

Variations inemmType among Group A Streptococcal Isolates Causing Invasive or Noninvasive Infections in a Nationwide Study

“…In agreement with previous studies, we found that the emm type distribution differed significantly between the different patient categories, which demonstrates a potential association between emm types and the kinds of infections (2,5,23). However, it should be recognized that although the differences may be explained by relative oversampling of some regions for invasive isolates or noninvasive isolates relative to the other, it seems unlikely that it could be the only explanation.…”

Roles of the plasminogen activator streptokinase and the plasminogen-associated M protein in an experimental model for streptococcal impetigo

“…Decades of epidemiological findings support the existence of GAS strains that have strong preferences for either the throat or skin, as well as other strains whose tissue site preference is less clear cut (Anthony et al, 1976 ;Bisno & Stevens, 2000 ;Maxted, 1980 ;Wannamaker, 1970). Thus, there should exist tissuespecific genotypes among GAS strains.…”

Local changes in rates of groupA Streptococcus disease and antibiotic resistance are associated with geographically widespread strain turnover events

“…21 While it has been suggested that turnovers in military populations simply represent the effect of training class turnover events, 20 the data suggest otherwise. The sites studied here experience constant training class turnover, with approximately 10% of the recruit population being replaced weekly, yet specific emm types often dominate specific sites for periods of several months.…”

“…Dynamic epidemiology, characterized by rapid turnover between dominant strains, is the recognized pattern for GAS. 20,21 However, the scale on which these turnovers occur has not been well studied. Complete turnover between single dominant strains was seen in a small, somewhat isolated population of children, 21 while less succinct dynamic events were also seen in military recruits.…”

“…20,21 However, the scale on which these turnovers occur has not been well studied. Complete turnover between single dominant strains was seen in a small, somewhat isolated population of children, 21 while less succinct dynamic events were also seen in military recruits. 20 The authors of those studies attributed the turnover events to different factors-herd immunity and close contact in the first case, constant turnover of the population in the second.…”