A bundle of infection control measures reduces postoperative sternal wound infection due to Staphylococcus aureus but not Gram-negative bacteria: a retrospective analysis of 6903 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: To assess the impact of an evolving infection control programme on the incidence of sternal wound infection (SWI), and the changing incidence of non-staphylococcal infections. METHODS: A retrospective cohort study of all patients who underwent primary sternotomy at a single UK centre between September 2010 and May 2018 was undertaken. Data were collated from the 2 years preceding the stepwise introduction of a broad-ranging infection control programme, including S. aureus decolonization. FINDINGS: In total, 6903 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 programme 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 cases of S. aureus infection, with no discernible impact on GNB. Multi-variable logistic regression analysis identified coronary artery bypass grafting, procedural urgency, and procedures performed in the third quarter of the calendar year (July to September) as independent risk factors for postoperative infection. CONCLUSION: A multi-faceted infection control programme 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 GNB infections when measuring effectiveness.

MBL2 deficiency is associated with higher genomic bacterial loads during meningococcemia in young children.

Mannose binding lectin (MBL2) is a soluble pattern recognition receptor that is key to generating innate immune responses to invasive infection, including against the cardinal Gram-negative bacterium Neisseria meningitidis. Individuals homozygous or heterozygous for any of three variant alleles of MBL2 (O/O or A/O genotypes) have deficient concentrations of MBL2 in circulating blood, but previous studies linking MBL deficiency to susceptibility to meningococcal disease have not revealed a consistent association. We genotyped 741 patients with microbiologically-proven meningococcal disease and correlated MBL2 genotype with plasma bacterial load of N. meningitidis with blood samples taken during hospital admission. We show that individuals with genotypes compatible with MBL2 deficiency have higher measurable levels of bacterial plasma genomic load with the greatest effect seen in children <2 years of age. However, the overall impact of this is minor, because there was no evidence that such genotypes are more common in children with meningococcal disease compared with uninfected cohorts. The findings suggest that MBL2 supports innate immune defence against meningococcal disease in the early months of life, before acquired immunity is sufficiently robust for effective natural protection.