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Streptococcal skin infection and acute glomerulonephritis.

Introduction The role of streptococcal skin and soft tissue infections in the development of acute glomerulonephritis (AGN) is now clearly established. Among the early studies comparing the epidemiology of AGN and rheumatic fever it was noted that the former complication often followed deep or suppurative streptococcal infection, including wound infection, whereas rheumatic fever was commonly associated only with superficial pharyngeal infections. Impetigo, erisipelas and wound infections were all incriminated as antecedent infections of AGN in early studies (Dillon, 1967). Furthermore, as recently postulated (Wannamaker, 1970), the socalled 'trench nephritis', common during World War I, probably represented post-streptococcal AGN, with streptococcal skin or wound infection being of primary aetiologic importance. Interest in the role of skin infection in AGN appears to have been relatively dormant during the period of World War II and the immediate post-war era. In contrast, intensive interest in streptococcal pharyngeal infection was evident and it was during this period that the relation between streptococcal pharyngitis and acute rheumatic fever became unequivocally established (Rammelkamp, Denny & Wannamaker, 1952). Shortly thereafter the now classic studies of epidemic AGN following throat infection with streptococcal type M-12 led to the establishment of the concept of there being 'nephritogenic' strains of streptococci (Rammelkamp & Weaver, 1953). It soon became apparent from studies in widely different areas that limited serotypes of group A streptococci, notably M-types 1 and 12, accounted for most cases ofAGN following streptococcal sore throat (Wannamaker, 1967). Following the observations that led to the hypothesis of there being nephritogenic streptococci, epidemiologic studies of impetigo in Great Britain (Parker, Tomlinson & Williams, 1955) suggested that limited serotypes of streptococci, most of which were typable at that time only by slide agglutination serotyping (which identifies T-antigens, see below) accounted for most cases of impetigo. These investigators coined the term 'impetigo streptococci'. AGN was not reported in that particular investigation but it has become subsequently apparent that these studies represented a fundamental contribution to the understanding of differences in the epidemiology of streptococcal skin and pharyngeal infections. Sporadic reports of AGN following impetigo, most of which were from the south eastern area of the United States where impetigo has long been recognized to be a perennial problem during the warm and humid months of summer and early autumn, were notable in that the streptococci isolated from these patients were not further identified other than being beta-haemolytic organisms or group A streptococci. Limitations in ability to serotype the skin streptococci were clearly a problem in these investigations (Blumberg & Feldman, 1962; McCullough et al., 1951). In 1954, there occurred a significant epidemic of AGN at the Red Lake Indian Reservation in northern Minnesota. Two-thirds of the sixty-three patients reported to develop AGN were definitely considered to have pyoderma as the antecedent of that complication, with pharyngitis playing a minimal, if any, role in the outbreak (Kleinman, 1954). The epidemic peak ofAGN at Red Lake occurred in late summer when weather in that particular area is hot and humid, not unlike that experienced in the south eastern area of the United States. The first outbreak of AGN at Red Lake is perhaps best remembered because the epidemic strain of streptococcus proved to be a new serotype-M-49 (Updyke, Moore & Conroy, 1955) and was the first serotype of streptococcus found to be clearly related to AGN following skin infection. This strain, subsequently known as the Red Lake strain, has now been incriminated as a cause of skin infection and AGN in many parts of the world. During the mid 1960s renewed interest in the role of skin infection and AGN developed largely as a result of extensive investigations in three particular areas: Alabama, Red Lake and Trinidad. It is coright.