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Abdominal

Bacteraemia/no

Pelvic/obstetric

Abdominal

Bacteraemia/no

Pelvic/obstetric

Pictures Mrsa Behind Ears

Skin and soft tissue

Bone/joint

Upper respiratory tract

Pneumonia

Necrotising fasciitis

Figure 1.2 Clinical syndromes associated with invasive GAS disease. Adapted from data in Kristensen and Schonheyder (1995), Davies etal. (1996) and Zurawski etal. (1998).

Skin and soft tissue

Bone/joint

Upper respiratory tract

Pneumonia

Necrotising fasciitis

Figure 1.2 Clinical syndromes associated with invasive GAS disease. Adapted from data in Kristensen and Schonheyder (1995), Davies etal. (1996) and Zurawski etal. (1998).

Cellulitis, which spreads along the long axis of a limb, rather than in a centrifugal pattern, is more likely to be streptococcal than staphylococcal. Furthermore, cellulitis occurring in a butterfly distribution on the face (erysipelas) is almost always due to the GAS. Occasionally, cracks between digits, or behind the ears, reveal likely portals of entry. Large-colony GCS and GGS, as well as GBS, cause cellulitis, although the incidence of premorbid illness or advanced age is more common in these latter groups.

In some circumstances bacteria spread between the fascial planes, along fibrous and fatty connective tissues, which separate muscle bundles. This results in necrotising fasciitis (Plate 1), where connective tissues become inflammed and rapidly necrotic. In several recent series necrotising fasciitis has accounted for approximately 6% of all invasive GAS cases (Davies etal. 1996; Ben-Abraham etal. 2002). Streptococcal necrotising fasciitis often arises because of bacteraemic seeding into fascia underlying otherwise quite normal-looking skin. In some cases there is history of prior blunt trauma to an infected region. In other cases there is an obvious portal of entry, such as recent surgery or varicella. It is useful to distinguish streptococcal necrotising fasciitis from synergistic or mixed-infection necrotising infections. Streptococcal necrotising fasciitis often occurs as a pure infection and may arise in previously healthy individuals, often affecting the limbs, resulting in extreme pain in a febrile or septic patient. In contrast, synergistic necrotising fasciitis tends to follow surgery or debilitation and occurs in areas where enteric and anaerobic bacteria have opportunity to mix with normal skin flora, such as abdominal and groin wounds.

Although less common than skin and soft-tissue infection, puerperal sepsis with endometritis and pneumonia due to S. pyogenes still occur and should not go unrecognised (Zurawski etal. 1998; Drummond etal. 2000). Epiglottitis because of GAS infection is also well recognised in adults (Trollfors etal. 1998). Importantly, a significant proportion of invasive GAS disease occurs as isolated bacteraemia in a patient without other apparent focus. This does not obviate the need for careful inspection of the whole patient in an effort to rule out areas of tissue necrosis.

Predisposition to Invasive GAS Disease

Although capable of occurring during any stage of life, invasive GAS disease is more common in early (0-4 years) and later life (>65 years). As for the other P-haemolytic streptococci, incidence in males generally exceeds that in females (HPA 2003b).

Many underlying medical conditions have been associated with increased risk of invasive GAS disease (Table 1.4). Some, such as varicella, provide obvious portals of entry for the bacterium, whilst

Weekly count

Moving average (6 weeks)

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