Prognostic factors in patients hospitalised with group A Streptococcus bacteraemia in tropical Australia

Group A Streptococcus (GAS) bacteraemia is common in tropical settings and has a high case-fatality rate. Early recognition of the high-risk patient can expedite the escalation of care.

We examined consecutive episodes of GAS bacteraemia in Far North Queensland, tropical Australia between January 1, 2014, and December 31, 2020. The patients' demographics and clinical and laboratory indices at presentation were correlated with their subsequent clinical course.

There were 286 episodes of GAS bacteraemia. The patients' median (interquartile range) age at presentation was 60 (48-71) years, 154 (53.9%) were male, 169 (59.1%) identified as a First Nations Australian, 126 (44.1%) had severe comorbidity and 136 (47.6%) lived in a remote location. There were 50/286 (17.5%) who died or were admitted to the intensive care unit (ICU) admission within 30 days of hospitalisation. In multivariable analysis, systolic blood pressure <100 mmHg (adjusted odds ratio (aOR) (95% confidence interval (CI)): 5.67 (2.20 - 14.55), p<0.0001), serum lactate >4 mmol/L (aOR (95% CI)): 5.32 (1.92 - 14.72), p=0.001), a circulating lymphocyte count <0.5×10⁹/L (aOR (95% CI)): 2.68 (1.17 - 6.12) p=0.02) and a serum albumin <30 g/L (aOR (95% CI)): 2.24 (1.01 - 4.97), p= 0.049) at presentation were independent predictors of death or ICU admission within 30 days. There were 21/286 (7%) with a diagnosis of streptococcal toxic shock syndrome (STSS) and necrotising fasciitis; all 21 died or required ICU admission. Individuals with a diagnosis of STSS and/or necrotising fasciitis were more likely to die within 30 days than the individuals without STSS or necrotising fasciitis (8/21 (38.1%) versus 13/272 (4.8%), OR (95%): 26.56 (8.03 - 87.86), p < 0.0001).

Patients with GAS bacteraemia who have hypotension, raised serum lactate, lymphopenia and hypoalbuminaemia at presentation are at greater risk of a complicated course. Individuals with STSS and necrotising fasciitis are at the greatest risk of death, emphasising the importance of considering - and actively excluding - these diagnoses in the appropriate clinical context.