For a better experience, click the Compatibility Mode icon above to turn off Compatibility Mode, which is only for viewing older websites.

Institute for Molecular Medicine and Infectious Disease Center for Surgical Infections and Biofilms

Surgical site infections (SSI) are a major health care concern worldwide. Drexel University College of Medicine faculty have played a leading role in developing the biofilm paradigm that serves as the current rubric for understanding these chronic debilitating infections. Moreover the recognition that biofilms underlie the recalcitrance of these infections to treatment provides a framework for the development of rational treatment strategies. Led by Dr. Garth D. Ehrlich and Dr. Donald C. Hall, the program is a true interdisciplinary collaboration among faculty members from multiple Colleges and Departments throughout Drexel University that are focused on both better diagnostics and improved therapeutics. Housed within the Institute for Molecular Medicine and Infectious Disease and sharing space with the Center for Genomic Sciences and the Center for Advanced Microbial Processing the program benefits from access to state-of-the-art instrumentation in biofilm microbiology and metaomics.

About Surgical Infections

The Centers for Disease Control and Prevention replaced the term surgical wound infection with the term surgical site infection, in order to give a truer reflection of the range of infections associated with surgical procedures. These infections are classified into incisional or organ/space (other organ or space manipulated during an operation). The incisional infections are further divided into superficial (skin and subcutaneous tissue) and deep (deep soft tissue-muscle and fascia). Detailed criteria are given at the websites of CDC and Infectious Diseases Society of America (IDSA). These definitions are followed universally for surveillance, prevention, and control of surgical site infections.

Typically, SSI is an infection that develops within 30 days after an operation or under a special circumstance, or within one year if an implant was placed and the infection appears to be related to the surgery. SSI is responsible for about 15% of all nosocomial infections, and among surgical patients, it is the leading nosocomial infection. Post-operative SSI is the most common healthcare-associated infection in surgical patients, occurring in up to 5 percent of surgical patients. In the United States, between 500,000 and 750,000 SSIs occur annually. Patients who develop an SSI require significantly more medical care. If an SSI occurs, a patient is 60 percent more likely to spend time in the ICU after surgery than is an uninfected surgical patient, and the development of an SSI increases the hospital length of stay by a median of two weeks. The risk continues after discharge; the SSIs develop in almost 2 percent of patients after discharge and these patients are two to five times as likely to be readmitted to the hospital. (Whitehouse et al., 2002)

An increased morbidity and more need for hospital care associated with SSIs contribute to increased health care costs. In a case-control study, patients with methicillin-resistant Staphylococcus aureus (MRSA) SSI had median hospital charges of $92,363, which was $62,908 more than the median charge for the control group of uninfected surgical patients. (Engermann et al., 2003) Mean attributable costs for SSI were $25,546 in a recent analysis of published studies on SSI costs. Other studies have estimated excess costs to range from $3,089 to a mean of $35,367 for MRSA infection. (Stone et al., 2002; 2008) Here, the increased cost is not confined to economic costs, because SSIs also contribute significantly to mortality. More than 20,000 deaths per year are due to SSIs, and the chance of death in a surgical patient is doubled if an SSI occurs. (Kirkland et al., 1999) The increased mortality is even more pronounced after coronary bypass surgery, where deep-chest SSI is associated with a mortality rate of 22 percent compared with 0.6 percent in those without an SSI. (Hollenbeak et al., 2000)

Prevention of SSI requires addressing the causes. Although some of the risks are difficult to control, adequate skin antisepsis is a promising way to decrease rates of SSI, because contamination from bacteria at the surgical site is a necessary precursor to infection. (Mangram et al., 1999; Pottinger et al., 2006) CDC recommend the use of hand hygiene, skin antisepsis and surgical instrument and environment management (among other interventions) to reduce the risk of SSI. The most commonly used skin antisepsis agents are iodine- and alcohol-based products and chlorhexidine gluconate (CHG). Alcohol-based products are effective, inexpensive, and readily available but are potentially flammable and can irritate the skin. CHG and iodine-based products both have a broad spectrum of activity, but CHG leads to greater reductions in skin microflora and offers greater residual activity. Furthermore, CHG is not inactivated by blood or serum proteins as are iodine-based antiseptic products. A persistence of CHG on the skin allows prolonged and cumulative antibacterial effect. (Mangram et al., 1999; Paulson et al., 1993) At the same time a slow but steady rise in antibiotic-resistant pathogens is noticed over past few decades. This invites an innovation of newer technology to combat SSI and the upcoming bad bugs.

The Food and Drug Administration (FDA) requires that antiseptics demonstrate a rapid 3.0 log10 reduction from baseline on a groin test site, a 2.0 log10 reduction on an abdomen test site, and they must maintain effectiveness for at least six hours after application.(FDA, 1994) Although the need for skin antisepsis is well accepted, a few practical problems are associated with patient participation. (Mangram et al., 1999) Given below are the links for additional information on SSI.

 Back to Top

Current Research Activity Related to Surgical Infections

  • Clinical and molecular epidemiology of SSI and database
  • Wound infection and healing pathogenesis and host responses
  • Bacterial biofilms

 Back to Top

Review Articles on SSI

 Back to Top

Participating Faculty

 Back to Top