A woman with an infected cat bite died from sepsis after she was sent home from hospital without the proper treatment.
Newham General Hospital has apologised over the death of 61-year-old Gabriele Kreichgauer.
A junior doctor who saw her searched for "cat bite" on an internet database but was directed to cat scratch fever, which has different treatment.
She was discharged without antibiotics and died two days later.
Barts Health NHS Trust, which runs the east London hospital, said: "We are sorry for the failings in the care we gave to Ms Kreichgauer."
Philip Barlow, assistant coroner for Inner South London, said in a prevention of future deaths report that when Ms Kreichgauer visited A&E on 21 January 2018, the junior doctor used a paid-for internet database called Uptodate.
Mr Barlow said when the doctor was directed to cat scratch fever he planned to prescribe the antibiotic azithromycin - but that was not given to Ms Kreichgauer.
However, the coroner said the appropriate treatment for the cat bite on her hand was different and "even if she had been given antibiotics it is therefore likely that these would not have been effective".
Mr Barlow said the reason Ms Kreichgauer was discharged from hospital without any antibiotics "appears to have been that no-one did a final check on what treatment was considered and whether this had been given to her".
Ms Kreichgauer went on to develop sepsis and died at the Queen Elizabeth Hospital on 23 January.
Barts Health NHS Trust said: "Having investigated the causes we have reviewed our processes and put systems in place to provide safe clinical care, as well as having contacted UpToDate - an approved medical resource database - to improve its indexing to encourage selection of the appropriate disorder."