when was the first time patient 32163 had a microbiology test, since 79 months ago?
select microbiologyevents.charttime from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 32163 ) and datetime(microbiologyevents.charttime) >= datetime(current_time,'-79 month') order by microbiologyevents.charttime asc limit 1