what was the organism that was discovered in the last sputum microbiology test of patient 12775 this month?
select microbiologyevents.org_name from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 12775 ) and microbiologyevents.spec_type_desc = 'sputum' and microbiologyevents.org_name is not null and datetime(microbiologyevents.charttime,'start of month') = datetime(current_time,'start of month','-0 month') order by microbiologyevents.charttime desc limit 1