Document Type


Date of Degree

Spring 2016

Degree Name

MS (Master of Science)

Degree In


First Advisor

Herwaldt, Loreen

First Committee Member

Petersen, Christine

Second Committee Member

Chrischilles, Elizabeth


Background. Surgical site infections (SSIs) cause many adverse outcomes for patients including increased length of hospital stay, hospital costs, morbidity, and psychological distresses. Staphylococcus aureus is one of the most common causes of SSIs in the United States.

Objective. Identify risk factors for Staphylococcus aureus SSIs following breast operations.

Design. Retrospective nested case-control study of SSIs among women undergoing breast operations.

Setting. An academic health center.

Patients. We studied patients undergoing breast operations at the University of Iowa Hospitals and Clinics from 7/1/2004 through 9/30/2015. Cases were patients who acquired SSIs meeting the National Healthcare Safety Network definition and whose SSIs were caused by S. aureus. We randomly selected two controls for each case from patients who had breast operation during the study period and did not meet the SSI definition. Controls were selected randomly from uninfected patients whose operations occurred during the same month and year as a case.

Results. Forty two (1.2%) patients acquired S. aureus SSIs after 3494 breast operations. SSIs were identified a mean of 27.8 days after the breast operations; 54.76% were deep incisional infections. Poisson regression analysis revealed that S. aureus SSIs following breast operations at UIHC have been increasing at a statistically significant rate. Bivariable analysis identified several patient and procedure related risk factors that increased the risk for S. aureus SSIs. Patient-related factors included a diabetes mellitus, active skin disease, prior chemotherapy, breast cancer, hypertension, and preoperative hemoglobin. Procedure-related factors included ASA score > 2, a mastectomy followed by immediate reconstruction, sentinel lymph node biopsy (SLN), drain placement, procedure time, and estimated blood loss. A multivariable analysis of patient factors found only breast cancer maintained significance. A similar analysis of procedure factors found that drain placement remained significant. The combined model contained breast cancer, drain placement, and mastectomy followed by immediate reconstruction as significant variables.

Conclusions. S. aureus SSIs following breast operations have been increasing at UIHC. Possible remediable risk factors include blood glucose levels, blood pressure, timing of chemotherapy, and drain placement and care. These results will help doctors at UIHC design interventions to prevent S. aureus SSIs following these procedures.

Public Abstract

This study examined risk factors for infections caused by the staph bacteria following breast operations. Patient factors that increased the infection risk included a diagnosis of diabetes, high blood pressure, chemotherapy before the procedure, and breast cancer diagnosis. Procedural factors that increased the risk of infection included having a mastectomy followed by immediate reconstruction and drain placement.

Patients who had infections of their operative sites were compared with patients that did not acquire infections. Patient and procedural risk factors affected a patient’s risk of infection. Diabetes, high blood pressure, chemotherapy before the procedure, breast cancer diagnosis, mastectomy with immediate reconstruction, and drain placement were all factors that contributed to the risk of SSI following breast operations at UIHC.


publicabstract, hospital, infection, site, Staphylococcus aureus, surgical


viii, 35 pages


Includes bibliographical references (pages 33-35).


Copyright 2016 Elaina O'Neill