A bundle of infection control measures reduces post-operative sternal wound infection due to Staphylococcus aureus but not Gram-negative bacteria : a retrospective analysis of 6,903 patient episodes

Background

Prevention of cardiac surgical site infection has largely focused on reducing infection due to Staphylococcus aureus although other bacteria also play an important role in this complication.

Aim

We assess the impact of an evolving infection control program on the incidence of sternal wound infection (SWI) and the changing incidence of non-staphylococcal infections.

Methods

We conducted a retrospective cohort study of all patients who underwent primary sternotomy at a single UK centre between September 2010 and May 2018. Data were collated from two-years prior to the stepwise introduction of a broad-ranging infection control program, including S. aureus decolonisation.

Findings

6,903 primary sternotomies were performed of which 2.6% (n=178) were complicated by SWI. Gram-negative bacteria (GNB) and S. aureus were most commonly identified as causative pathogens (45.5% and 30.3% respectively). Following program introduction there was a reduction in the rate of SWI from 3.9 to 1.8 cases/100 patients/month. This was mainly due to a sustained reduction in S. aureus infected cases with no discernible impact on GNB. Multivariable logistic regression analysis identified coronary artery bypass grafting, procedural urgency and procedures performed in the 3rd quarter as independent risk factors for post-operative infection.

Conclusion

A multifaceted infection control program was successful at reducing the rate of SWI primarily due to a reduction in S. aureus infections. GNB also play an important role in SWI and traditional preventative measures fail to address these. Future intervention and impact assessments should consider Gram negative infection when measuring effectiveness.