when did the last microbiology test of patient 26175 in 04/this year be performed?
select microbiologyevents.charttime from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 26175 ) and datetime(microbiologyevents.charttime,'start of year') = datetime(current_time,'start of year','-0 year') and strftime('%m',microbiologyevents.charttime) = '04' order by microbiologyevents.charttime desc limit 1