what was the number of patients that were tested in 2103 for catheter tip-iv microbiology?
select count( distinct admissions.subject_id ) from admissions where admissions.hadm_id in ( select microbiologyevents.hadm_id from microbiologyevents where microbiologyevents.spec_type_desc = 'catheter tip-iv' and strftime('%y',microbiologyevents.charttime) = '2103' )