Dr Andrew Whitelaw, President of the Infection Control Society of Southern Africa.
With acknowledgments to Sr C Rinquest, Dr J Wojno and Dr V Madikae who have been involved in the ongoing investigation of the outbreak.
The cardiac surgeons inform you, the infection control practitioner, about a possible outbreak of Staphylococcus aureus post-operative wound sepsis. In the last 2 months, 6 patients have developed S. aureus sepsis post operatively. They now contact you to demand that you investigate the outbreak, that you swab every staff member and patient, as well as testing the operating theatre for contamination.
A summary of the cases is as follows:
Case 1: Surgeon Dr A; assistant Dr Z, anaesthetist Dr G
Superficial wound sepsis 1 week after surgery. S. aureus (cloxacillin resistant) isolated from wound swabs.
Case 2: Surgeon Dr B, assistant Dr Z, anaesthetist Dr F
Deep surgical site infection and septic pericarditis 10 days post-operatively. S. aureus (cloxacillin susceptible) isolated from pericardial fluid and blood cultures.
Case 3: Surgeon Dr A, assistant Dr Z, anaesthetist Dr F.
Deep surgical site infection about 3 weeks post operatively. S. aureus isolated from tissue, resistant to cloxacillin.
Case 4: Surgeon Dr C, assistant Dr X, anaesthetist Dr G
Deep surgical site infection and S. aureus bacteraemia 6 days after surgery. S. aureus susceptible to cloxacillin
Case 5: Surgeon Dr B, assistant Dr X, anaesthetist Dr E
Deep surgical site infection 4 days post operatively. S. aureus isolated, sensitive to cloxacillin.
Case 6 Surgeon Dr C, assistant Dr Z, anaesthetist Dr B
Deep surgical site infection 17 days post operatively. S. aureus (cloxaciliin susceptible) isolated from swabs.
Three of the isolates were available for molecular analysis, and the result is shown below.
Pulsed field gel electrophoresis of S. aureus genomic DNA digested with SmaI
Lane 1: MW marker
Lane 2: NCTC 8325 (ref strain)
Lane 3: Isolate from Case 2
Lane 4: Isolate from Case 4
Lane 5: Isolate from Case 5
Question 1: What are the basic principles involved in investigating an outbreak such as this?Continue to Answer 1