Coagulase-negative staphylococci are frequently isolated from clinical specimens and they represent the most common cause of bacteraemia in hospitalised patients. Particularly, venous catheter-related bloodstream infections are often due to non-aureus staphylococci. These are opportunistic pathogens in immunocompromised hosts and may behave as reservoirs of antibiotic resistance determinants.1

A 75-year-old woman was admitted to hospital because of diffuse bone pain. A relapse of myeloid acute leukaemia was diagnosed (the first diagnosis had been made 5 months earlier), and she was admitted to the haematology department. Nine days later she developed fever (to 39°C) and chills. A Gram-negative infection was suspected, and blood samples (the set included two BacT/Alert aerobe/yeast bottles (bioMérieux, Marcy l’Etoile, France) plus one anaerobe bottle) were taken for culture. A second set (including two BacT/Alert aerobe/yeast bottles, without the anaerobe bottle) was taken after 30 min, and meropenem treatment was started (1 g every 8 h, intravenous). Due to persistence of fever, meropenem was replaced with piperacillin–tazobactam (4.5 g every 8 h, intravenous) 2 days later. After 48 h incubation, all of the samples were detected as positive by the BacT/Alert; Gram staining showed Gram-positive cocci, and cultures yielded Staphylococcus pasteuri as a single organism; typical yellow colonies were observed after 24 h incubation under aerobic and anaerobic conditions. The species was initially identified as Staphylococcus warneri …