Morbidity and mortality in critically ill patients with invasive group A streptococcus infection: an observational study

Abstract

Background: Group A streptococci (GAS) are known to cause serious invasive infections, but little is known about outcomes when patients with these infections are admitted to intensive care. We wanted to describe critically ill patients with severe sepsis or septic shock due to invasive GAS (iGAS) and compare them with other patients with severe sepsis or septic shock.

Methods: Adult patients admitted to a general intensive care unit (ICU) in Sweden (2007-2019) were screened for severe sepsis or septic shock according to Sepsis 2 definition. Individuals with iGAS infection were identified. The outcome variables were mortality, days alive and free of vasopressors and invasive mechanical ventilation, maximum acute kidney injury score for creatinine, use of continuous renal replacement therapy and maximum Sequential Organ Failure Assessment score during the ICU stay. Age, Simplified Acute Physiology Score (SAPS 3) and iGAS were used as independent, explanatory variables in regression analysis. Cox regression was used for survival analyses.

Results: iGAS was identified in 53 of 1021 (5.2%) patients. Patients with iGAS presented a lower median SAPS 3 score (62 [56-72]) vs 71 [61-81]), p < 0.001), had a higher frequency of cardiovascular cause of admission to the ICU (38 [72%] vs 145 [15%], p < 0.001) and had a higher median creatinine score (173 [100-311] vs 133 [86-208] μmol/L, p < 0.019). Of the GAS isolates, 50% were serotyped emm1/T1 and this group showed signs of more pronounced circulatory and renal failure than patients with non-emm1/T1 (p = 0.036 and p = 0.007, respectively). After correction for severity of illness (SAPS 3) and age, iGAS infection was associated with lower mortality risk (95% confidence interval (CI) of hazard ratio (HR) 0.204-0.746, p < 0.001). Morbidity analyses demonstrated that iGAS patients were more likely to develop renal failure.

Conclusion: Critically ill patients with iGAS infection had a lower mortality risk but a higher degree of renal failure compared to similarly ill sepsis patients. emm1/T1 was found to be the most dominant serotype, and patients with emm1/T1 demonstrated more circulatory and renal failure than patients with other serotypes of iGAS.

Keywords: Group A streptococcus; Intensive care unit; Sepsis; emm1/T1-type.

Fig. 1

Flowchart of the patient cohort

Fig. 2

Distribution of emm- and T-type in iGAS isolates. Before 2012, at the Clinical Microbiology Laboratory in Lund, T-typing was performed to determine the serotype of GAS. After 2012, this was replaced by emm-typing. T-type 1 correlates to emm-type 1; other comparisons between T-type and emm-type are more complex