what is the first specimen test given to patient 7375 in 04/2100?
select microbiologyevents.spec_type_desc from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 7375 ) and strftime('%y-%m',microbiologyevents.charttime) = '2100-04' order by microbiologyevents.charttime asc limit 1