instruction: how many patients have had a blood culture ( myco/f lytic bottle) test since 4 years ago?
response: 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 ( myco/f lytic bottle)' AND DATETIME(microbiologyevents.charttime) >= DATETIME(CURRENT_TIME(), '-4 year'))