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Department of Surgery Surgical Infections Research

Surgical site infection (SSI) is a major health care concern. At Drexel University College of Medicine, a surgical infections research initiative is part of the surgical research programs. Led by Dr. Suresh Joshi, the program is a true cross-disciplinary collaboration between faculty members from multiple departments, including the Institute for Molecular Medicine and Infectious Disease. The program has a classical biological safety level-2 facility, molecular and cell biology laboratory, and small and large animal surgery facilities for infection models.

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. 

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Surgical Infections and Acinetobacter baumannii

Acinetobacter baumannii infections are associated with high morbidity, mortality, and multi-resistance. Acinetobacter baumannii is the third commonest gram-negative pathogens responsible for hospital-acquired infections and especially surgical site infections. Intensive Care Unit (ICU) patients are at great risk of developing such infection, and the isolates are often multidrug-resistant (MDR), virulent and strong biofilm producers. Mortality is almost double in the patients having infections with MDR isolates versus non-resistant isolates (~61% versus 31%). High incidence of multi-resistance is attributable to severe underlying disease and comorbidities, inappropriate use of broad-spectrum antibiotics, mechanical ventilation, utilization of devices and interventional techniques, and prolonged hospital stay; therefore significant differences in rate of occurrence are also identified, even within different wards of the same hospital. Current knowledge about the molecular and clinical epidemiology of such MDR isolates is important for treatment and to control their spread. Carbapenems (such as imipenem, meropenem, and doripenem) was a last resort for such situations. Recently, carbapenem-resistant Acinetobacter baumannii (CRAB) started appearing in the United States hospitals, and many of them are very dangerous (pan-drug resistant variants), and polymyxin, such as colistin is the only drug to which they are susceptible. New antimicrobial agents with activity against Acinetobacter baumannii are not likely to be available in the immediate near future, making ongoing surveillance of the activities of currently available agents very important. Moreover, studies that address potential risk factors and underlying molecular mechanisms would greatly improve our understanding of the epidemiology of antimicrobial resistance in institutions and guide efforts to develop more effective strategies for prevention and treatment (Katsaragakis et al, 2008). Carbapenem resistance is steadily increasing in A. baumannii, a member of Enterobacteriaceae, and has almost doubled in last few years. CDC has prioritized its curb.

Acinetobacter baumannii infection includes respiratory tract infection, meningitis, peritoneal cavity infection, urinary tract infection, ventilator-associated pneumonia (also known as nosocomial pneumonia), infections associated with continuous ambulatory peritoneal dialysis (CAPD), or catheter-associated bacteruria, and burns and wound infections (Joshi SG et al, 1998; 2006). The presence of Acinetobacter isolates in respiratory secretions in intubated patients nearly always represents colonization. Acinetobacter pneumonias occur in outbreaks and are usually associated with colonized respiratory-support equipment or fluids. Nosocomial meningitis may occur in colonized neurosurgical patients with external ventricular drainage tubes (Cunha BA, 2013). More clinical information can be found at A. baumannii and Surgical Infections.

A. baumannii is a multi-resistant aerobic gram-negative bacillus sensitive to relatively very few antibiotics. The organism has genetic capabilities to acquire or donate resistance gene, and thus later spread is major risk. A. baumannii is popular for R-plasmid mediated resistance and is also known as a reservoir of resistance plasmids (Joshi SG lab 2003, 2004, 2009, 2013).

Currently our laboratory is focusing on exploring underlying molecular mechanisms of carbapenem resistance in A. baumannii (CRAB), pathogenesis of Acinetobacter baumannii infection, and their control strategies. Understanding the approaches to control biofilm is one of the major paradigms.

Dr. Suresh G. Joshi

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Current Research Activity Related to Surgical Infections

  1. Development of antimicrobial locks, antimicrobial solution, and dressing material, using floating electrode-dielectric barrier discharge (FE-DBD) non-thermal plasma. FE-DBD plasma application is Drexel University's patented technology.
  2. Novel antimicrobial dressings to prevent and manage wound infection.
  3. Exploring newer antimicrobial agents against multidrug resistant Acinetobacter baumannii infection.
  4. Clinical and molecular epidemiology of SSI and database.
  5. Wound infection and healing pathogenesis, and host responses.
  6. Bacterial biofilms.

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Review Articles on SSI

  1. Reducing surgical site infections: a review
  2. Factors influencing antibiotic prophylaxis for surgical site infection prevention in general surgery: a review of the literature
  3. Preventing surgical site infection. Where now?
  4. Surgical site infections: how high are the costs?
  5. Clinical: Culture Negative Surgical Site Infections
  6. Surgical infections
  7. Surgeon's views: Current Issues in the Prevention and Management of SSI - Part 1 (Medscope Today)

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Participating Faculty

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Close-up of gloved hands passing the surgical scissors.