tell me the name of the organism found in patient 92788's first foot culture microbiology tests since 07/2105?
select microbiologyevents.org_name from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 92788 ) and microbiologyevents.spec_type_desc = 'foot culture' and microbiologyevents.org_name is not null and strftime('%y-%m',microbiologyevents.charttime) >= '2105-07' order by microbiologyevents.charttime asc limit 1