when was the first sputum microbiology test performed for patient 12410?
select microbiologyevents.charttime from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 12410 ) and microbiologyevents.spec_type_desc = 'sputum' order by microbiologyevents.charttime asc limit 1