###HUMAN: what was the first time that patient 031-24513 got a microbiology test?, ###ASSISTANT: SELECT microlab.culturetakentime FROM microlab WHERE microlab.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '031-24513')) ORDER BY microlab.culturetakentime LIMIT 1