Speciation of coagulase-negative staphylococci: A cohort study on clinical relevance and outcomes.

INTRODUCTION

Coagulase-negative staphylococci (CoNS) are common causes of bloodstream infections (BSI), but species-specific epidemiology is under-researched. This study aimed to examine the occurrence, clinical features, and outcomes of CoNS BSI in a large Australian population.

METHODS

All incidents of CoNS BSI in the Queensland Health system (2000-2019) were included.

RESULTS

Among 4046 CoNS BSI cases, 3353 were monomicrobial, with S. epidermidis (n = 1665), S. haemolyticus (n = 224), S. hominis (n = 220), S. capitis (n = 185), S. lugdunensis (n = 57), S. warneri (n = 47), and other species (n = 38). In 27% of cases, CoNS isolates were not assigned to species. Significant differences in age, onset classification, co-morbidities, and flucloxacillin resistance were observed across species. S. epidermidis, S. haemolyticus. S. capitis were predominantly hospital-onset, while S. lugdunensis was community-associated. The cohort had Charlson scores indicating high co-morbidity, with malignancy common among S. haemolyticus patients. Most speciated isolates of CoNS demonstrated resistance to flucloxacillin (2224/2827; 79%). The 30-day mortality rate was higher for polymicrobial (14%) vs. monomicrobial BSI (11%), p = 0.024. Mortality varied by species and was highest for S. lugdunensis (22%).

CONCLUSIONS

These findings underscore the value of species-level identification in managing CoNS BSIs, particularly in cases with clinical signs and symptoms, to support antimicrobial stewardship.