when did patient 1272 last take his or her tracheal aspirate microbiology test since 99 months ago?
select microbiologyevents.charttime from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 1272 ) and microbiologyevents.spec_type_desc = 'tracheal aspirate' and datetime(microbiologyevents.charttime) >= datetime(current_time,'-99 month') order by microbiologyevents.charttime desc limit 1