Case 2: Use to improve AMS (Surgical Site Infection)

In this final case study, Professor Alqahtani presents a patient case study in which the appropriate use of syndromic testing resulted in improved patient outcome.

Case summary

A 54-year-old woman is re-admitted to hospital with suspected deep sternal surgical site infection (SSI) following surgical repairs on her heart. Her patient history includes:

• History of rheumatic fever
• Received prophylactic antibiotic
• Type 2 diabetic

Upon examination, findings included:

• Febrile — with a high-grade fever (40°C)
• Hypotensive (blood pressure: 90/60 mmHg)
• Tachycardic (heart rate: 120 beats per minute)
• Lungs showed decreased breath sounds on the left side; no rubs (i.e. raspy breathing sounds due to inflammation)
• Sternum examination: purulent discharge, unstable
• Initial laboratory results also showed leukocytosis (WBC count: 18,000 cells/uL), and renal impairment (creatinine: 2.1 mg/dL), with elevated lactate (3.1 mmol/L)
• Patient likely septic (further complicated by her cardiac history)

Blood cultures were drawn, the infectious disease department was consulted and gram staining of the purulent drainage requested initially.

Case resolution

Taking an RDT approach afterwards (MALDI-TOF followed by PCR for confirmation of the pathogen and identification of resistance gene(s)) gave fast (within 16 hours) confirmation of a causative Methicillin-sensitive S. aureus (MSSA) pathogen. This meant that antibiotic therapy could be switched from vancomycin (prescribed as staphylococci suggested by gram stain) to a beta-lactam antibiotic.