when patient 99080 had their first staph aureus screen microbiology test since 180 months ago?
select microbiologyevents.charttime from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 99080 ) and microbiologyevents.spec_type_desc = 'staph aureus screen' and datetime(microbiologyevents.charttime) >= datetime(current_time,'-180 month') order by microbiologyevents.charttime asc limit 1