what was the organism that was found in the last microbiology test of patient 24894's blood culture (post-mortem)?
select microbiologyevents.org_name from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 24894 ) and microbiologyevents.spec_type_desc = 'blood culture (post-mortem)' and microbiologyevents.org_name is not null order by microbiologyevents.charttime desc limit 1