Heteroresistance to cefepime in Pseudomonas aeruginosa bacteraemia

•A high prevalence (57.3%) of cefepime heteroresistance (FEP-HR) was observed between 2011–2016.•Mechanistic analysis revealed that AmpC hyperproduction may have contributed to FEP-HR Pseudomonas aeruginosa bacteraemia.•Patients with advanced age, haematological malignancy, central venous catheter, and previous therapy with cephalosporins were identified as independent risk factors for acquiring FEP-HR P. aeruginosa bacteraemia.•Patients infected with FEP-HR were generally at greater risk of having an adverse prognosis than those with non-FEP-HR.•This study provides the first clinical evidence in vivo that cefepime heteroresistance in P. aeruginosa can be regarded as an intermediate stage for evolving from susceptibility to full resistance during antibiotic treatment.