Patients with emm1/T1 serotype invasive group A streptococci infections demonstrated more renal failure than patients with other serotypes: perhaps we should consider some confounders.

We read with great interest the article by Björck et al. who concluded that in their study of critically ill patients with invasive group A streptococcal (iGAS) infections, emm1/T1 was the most dominant serotype and that patients with that serotype demonstrated more circulatory and renal failure than patients with other serotypes of iGAS [1]. We would like to make some comments. Intravenous immunoglobulins (IVIGs) are often used as a part of the treatment of iGAS [1]. We noted that 52% of the emm1/T1 serotype patients received IVIGs as compared to 28% of the patients with other serotypes [1]. The incidence of acute kidney injury (AKI) with IVIGs stabilized with glucose, maltose, d-sorbitol, mannitol, glycine, or l-proline has been found to be lower than that with sucrose-stabilized products [2]. AKI induced by sucrose-containing IVIGs is likely related to the toxic action of sucrose on the nephron, whereby excess sucrose in the kidney causes osmotic nephrosis [2, 3]. Whilst osmotic nephrosis has been reported with sucrose-free IVIGs, the incidence is much lower because the levels of these agents can be closely regulated by enzymes within the kidney [2, 4]. Similarly to sucrose, excessive glucose accumulation can have deleterious effects on the proximal tubules [5] and, since intravenous glucose infusion is known to produce a rapid increase in blood glucose and insulin levels in normal subjects, diabetic patients are at particular risk of AKI following administration of glucose-stabilized IVIGs [2]. The incidence of diabetes mellitus is not reported in the paper of Björck et al. [1]. It is possible that the increase of AKI in the emm1/T1 serotype group was due to IVIGs. It would be very interesting to know if the IVIGs given to patients in this study were sucrose-stabilized.