instruction: calculate the number of patients that had a staph aureus screen microbiology test since 2102.
response: SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT microbiologyevents.hadm_id FROM microbiologyevents WHERE microbiologyevents.spec_type_desc = 'staph aureus screen' AND STRFTIME('%y', microbiologyevents.charttime) >= '2102')