what was patient 16571's first prescribed time for mupirocin nasal ointment 2% on the first hospital visit?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 16571 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) and prescriptions.drug = 'mupirocin nasal ointment 2%' order by prescriptions.startdate asc limit 1