Group A streptococci in the 1990s

The last decade has witnessed a remarkable change in the epidemiology of gr oup A streptococcal infections. There has been a marked increase globally i n the reporting of invasive infections caused by Streptococcus pyogenes, La ncefield group A streptococci. Many of these cases were deep-seated infecti ons associated with shock and multi-organ failure and are defined as strept ococcal toxic shock syndrome. In addition, reports of streptococcal sequela e, in particular, acute rheumatic fever, have re-emerged and remain a serio us health threat in developed countries. It appears that these infections a re related to the type distributions of the organism among the general popu lation, with the re-emergence of more 'virulent' strains, such as the M1 se rotype which in earlier decades was primarily seen in cases of either super ficial disease or scarlet fever. Population-based surveillance studies have clearly indicated the importance and relevance of type identification for epidemiological purposes. There have also been suggestions that certain ext racellular: products and toxins play a major role in the so-called 'increas ed virulence' of the organism; these include cell surface molecules such as the M protein, opacity factor, the hyaluronic acid capsule, C5a peptidase and streptococcal inhibitor of complement (SIC), in addition to secreted pr oteins, pyrogenic exotoxins, cysteine proteinase, streptolysins O and S, hy aluronidase, streptokinase and other enzymes. All these factors, and events during the last decade, strongly emphasize the need for a better understan ding of the epidemiology, pathogenesis, treatment and prevention of group A streptococcal infections.