instruction: what were the numbers of patients that received microbiology tests in the tissue during a year before?
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 = 'tissue' AND DATETIME(microbiologyevents.charttime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-1 year'))