58.09 Age-Related Microbiome Differences in Surgical Site Infections

Posted on January 31, 2019

R. Khatri2, T. L. Hedrick1, K. A. Popovsky1, R. G. Sawyer1,2  1University Of Virginia,Charlottesville, VA, USA 2Western Michigan University School of Medicine,Kalamazoo, MICHIGAN, USA

Introduction: Surgical site infections (SSI) contribute to overall morbidity and mortality of the surgical patient. There are numerous risk factors for the development of SSI. We propose that there are variations in the type of pathogen in SSI between different age groups.

Methods: We evaluated patients who underwent surgery at a university hospital from 1997 – 2017 that developed SSI. Patients were divided into age-related cohorts, age ≤ 45 years and age ≥65 years. We assessed immune response, disease severity, types of pathogens within wounds, mortality, and antibiotic therapy. Proportions were compared through use of chi square test and continuous variables were compared using Student’s t test.

Results: As compared to patients age ≥65 years who developed SSI (n=575), patients in age group ≤45 years (n=598) had increased leukocytosis (14.2K vs 13.4K, p=0.06), presence of fever (30.8% vs 20.9%, p<0.0001), and Tmax (37.9oC vs 37.6oC, p<0.0001) at time of diagnosis. Of those infections with positive growth on culture, patients age ≥65 years had higher percentage of Enterococcus spp (27.4% vs 17.5%; p=0.006) and P.aeruginosa (15.8% vs 9.6%; p=0.03) as primary wound pathogen as compared to those patients age ≤45 years. In addition, those patients age ≥65 had greater crude mortality rates (10.6% vs 2.7%; p<0.001). Those in age group ≤45 years had longer overall antibiotic treatment length (12.4 days vs 10.3 days, p<0.001) but were more likely to be prescribed oral antibiotics on discharge (51.3% vs 34.4%, p<0.0001).

Conclusion: Our data suggest that those in the older age group have less robust immune response and are colonized with more aggressive pathogens, which may require inpatient treatment with parenteral antibiotics. These findings may help tailor perioperative antibiotic prophylaxis according to age group and most common pathogens, and help prevent or improve overall morbidity from SSI.