count the number of patients who have received a blood culture (post-mortem) microbiology testing until 2100.
select count( distinct admissions.subject_id ) from admissions where admissions.hadm_id in ( select microbiologyevents.hadm_id from microbiologyevents where microbiologyevents.spec_type_desc = 'blood culture (post-mortem)' and strftime('%y',microbiologyevents.charttime) <= '2100' )