what was the organism that was detected during patient 74624's last catheter tip-iv test in their last hospital visit?
select microbiologyevents.org_name from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 74624 and admissions.dischtime is not null order by admissions.admittime desc limit 1 ) and microbiologyevents.spec_type_desc = 'catheter tip-iv' and microbiologyevents.org_name is not null order by microbiologyevents.charttime desc limit 1