has there been any microbiology test done on the current hospital visit to the catheter tip-iv of patient 2957?
select count(*)>0 from microbiologyevents where microbiologyevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 2957 and admissions.dischtime is null ) and microbiologyevents.spec_type_desc = 'catheter tip-iv'