[Correspondence] Heteroresistance and clinical outcomes: knowledge gaps

We read with interest the study published by Gabriel Heyman and colleagues in The Lancet Microbe,1 which retrospectively analysed 255 people with Escherichia coli bloodstream infections. The authors found that 109 (43%) of 255 E coli strains showed breakpoint-crossing heteroresistance (BCHR) for gentamicin and 22 (9%) of 255 strains for piperacillin–tazobactam. Although no correlation was observed between BCHR and length of hospital stay—the primary outcome—BCHR was associated with increased odds of intermediate or intensive care unit admission when patients received the antibiotic to which the strain was heteroresistant.