Review
Invasive group A streptococcal disease: should close contacts routinely receive antibiotic prophylaxis?

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Summary

Group A streptococci (Streptococcus pyogenes) causes a wide range of illnesses from non-invasive disease—eg, pharyngitis—to more severe invasive infections—eg, necrotising fasciitis and toxic shock-like syndrome. There remains uncertainty about the risk of secondary cases of invasive disease occurring among close contacts of an index case and how best to manage that risk. We do not consider that currently available evidence justifies the routine administration of chemoprophylaxis to close contacts. We suggest that the appropriate response should be to routinely inform all household contacts of a patient with invasive group A streptococcal disease about the clinical manifestations of invasive disease and to seek immediate medical attention if they develop such symptoms.

Introduction

Invasive group A streptococcal disease (iGAS) is defined as an infection associated with the isolation of Lancefield group A streptococci (Streptococcus pyogenes) from a normally sterile body site.1, 2, 3 Clinical presentation generally falls into one of three groups. The first is group A streptococcal toxic shock syndrome, which is differentiated from other types of iGAS by the occurrence of shock and multi-organ system failure early in the course of the infection. The second group is necrotising fasciitis (figure), characterised by extensive local necrosis of subcutaneous soft tissues and skin and the isolation of S pyogenes from a normally sterile body site. The third is a group of infections characterised by the isolation of S pyogenes from a normally sterile site in patients not meeting the criteria for streptococcal toxic shock syndrome or necrotising fasciitis. Included in this group are bacteraemia with or without an identified focus and focal infections such as meningitis, pneumonia, peritonitis, puerperal sepsis, osteomyelitis, septic arthritis, myositis, and surgical wound infections.

The epidemiology of iGAS is complex. S pyogenes are serologically classified according to the schemes described by Griffith4 and Lancefield5 based on the identification of T and M cell wall protein antigens. The M protein has always been considered to be the major virulence factor of S pyogenes infection. Therefore, most epidemiological studies of iGAS classify the organisms by M/emm type. The emm gene encodes the M protein and an emm gene sequence-based typing scheme has been developed and is now used extensively worldwide. More than 120 different M/emm types of S pyogenes exist, with M/emm 1 and M/emm 3 particularly associated with invasive infections. In the USA, approximately 10 000–15 000 cases of iGAS occur annually, with a 10–13% mortality rate. Clinical isolates examined by the Centers for Disease Control and Prevention (CDC) during the 1970s and 1980s showed a doubling in the prevalence of M/emm 1 and M/emm 3 serotypes during this period.6, 7 The 1990s saw a continuation of this global increase in the reporting of iGAS8, 9, 10 and was believed to be related to the serotype distributions of the organism among the general population, with a re-emergence of more virulent strains of the M/emm 1 serotype that in earlier decades were primarily seen in cases of either superficial disease or scarlet fever.10

It is well known that S pyogenes can spread from infected patients to close contacts. Against a background of an increase in incidence, the potentially severe clinical presentation, and the long-term sequelae of iGAS, this fact has resulted in a number of questions being directed at clinicians and public-health authorities concerning the risk of iGAS in close contacts of a case of iGAS (panel 1). Our objectives were to comprehensively review the literature to summarise the evidence of risk to close contacts of an index case of iGAS and to suggest an appropriate response to this risk.

Section snippets

Inclusion criteria

We included experimental studies, observational studies, and prospective surveillance studies from the USA, Canada, and European countries that identified possible host risk factors for the development of iGAS, studies that quantified risk to close contacts of cases, and studies that evaluated the potential effectiveness of antibiotic prophylaxis in preventing iGAS in close contacts. We also included case reports and opinions of committees and working groups to supplement observational and

Risk for sporadic disease

Many retrospective and prospective enhanced surveillance programmes that have been undertaken in the past 15–20 years show that iGAS is becoming an issue of increasing public-health importance both in the USA and in Europe (table).11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21

Although the individual surveillance studies that we reviewed had methodological limitations that would impact on the applicability of their findings, overall the data have been consistent in identifying underlying

Discussion

There is no doubt that the severity of iGAS, together with anecdotal reports of subsequent cases of disease in close contacts, generates concern and raises questions about a need for chemoprophylaxis in such contacts. Demand for decisive action by clinicians and public-health authorities is inevitable. The intuitive clinical response is to “do something” rather than “do nothing” when faced with the horrendous clinical picture of iGAS.

The evidence for chemoprophylaxis is limited. In terms of

Conclusions

The evidence base for informing definitive universal guidance on the management of close contacts of cases of iGAS is weak. The risk of iGAS in close contacts, while higher than the risk for sporadic disease, is still low and the benefit from antibiotic prophylaxis is not known. The routine administration of chemoprophylaxis to close contacts of cases of iGAS could be interpreted as offering too much apparent certainty, thereby offering false reassurance to contacts of cases of iGAS. Antibiotic

Search strategy and selection criteria

Data for this review were identified in December 2003 by searches of the Cochrane Library, National Health Service Centre for Reviews and Dissemination, Embase (1980 onwards), CINAHL (1982 onwards) and Medline (1966 onwards). The MeSH term “streptococcal infections” and subheading “/ep” was used. This MeSH heading search was refined by combination text word search using the term AND. These combination word searches included “group A”, “invasive”, “fasciitis”, “necrotising”, “streptococcal

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