76 An Overview of Methods to Reduce Surgical Site Infections

In the United States (US) alone 40 million surgeries take place every year. One of the major risks associated with surgery is infection of the surgical site. Surgical site infections (SSIs) have persisted since the first well documented surgeries in the 1800s and assuredly before that [1]. With a 1.5% mortality rate, tens of thousands of Americans die each year from SSI [1],[2].

Due to the severity of this problem, the Food and Drug Administration (FDA) has created presurgical preparation standards to decrease the risk of infection. These standards include the use of aseptic technique, sterilization of instruments, and cleansing of the patient’s skin [3], [4]. Of all these factors, the patient’s ownmicroflora remains the greatest cause of SSI [5]. Because of the skin bacteria’s potential risk, the FDA requires a pre-surgical reduction of surface skin bacteria by 2-3 log10 colony forming units (CFU) per cm2 and considers this sufficiently safe [2]. This requirement is met through preoperative skin preparation (PSP) kits. These PSP kits consist of alternating alcohol scrubs and either iodine or chlorohexidine gluconate (CHG). PSP kits have been approved by the FDA as a means to reduce skin surface bacteria, reducing the risk of SSI [6].

Even with FDA approved PSP methods, there remains a 2-5% risk of SSI [1]. This equates to 800,000 to 2 million patients every year in the US whose surgeries are complicated by SSI, 12 to 30 thousand of whom will die from these infections [2]. Not only is SSI potentially deadly but it also poses a significant financialburden to both the patient and the hospital. Infected patients have increased hospitalization length, higher readmission rates, and higher healthcare costs [7]. Although the daily costs of taking care of these patients is typically lower than an average hospital patient, their length of stay is significantly longer and the probability of returning within 30 days due to further complications is more than six times greater [7]. The financial burden of SSIs on hospitals encourages them to adopt better methods of skin preparation.

As new PSP methods are created, they must be tested to show how well they kill skin bacteria. To evaluate PSP kit efficacy, the “cup scrub method” quantifies bacterial reduction [7]. The cup scrub method consists of running a swab along the cleansed site to pick up any bacteria remaining on the surface. The swab is then placed in a sterile cup with broth. The solution of suspended bacteria is diluted (to allow for accurate quantification) and plated on agar to quantify the remaining bacteria [8]. All PSP scrub kits have been approved by this method. Unfortunately, because the cup scrub method only considers the surface of the skin, it neglects the presence of any bacteria residing deeper in the skin’s sweat glands, hair follicles, and sebaceous glands. The presence of these deeper-dwelling bacteria fails to show up on the traditional cup scrub tests. This explains why the risk of SSI remains so high even after PSP treatment [9].

Deeper dwelling bacteria can survive PSP treatment because they exist in more dormant forms than surface level bacteria. Because the surface of the skin is exceptionally dry most surface bacteria are only transient,existing on the skin only temporarily in a free-floating state [10]. Free floating bacteria are easily killed by antiseptic.In the deeper skin areas however, conditions are moist allowing the bacteria to form stable biofilms. Biofilms are interconnected communities of bacteria that provide more stable growth conditions. Because deep skin bacteria exist in biofilm phenotype, they are more resistant to antiseptic treatment [11].

Biofilm-based bacteria can withstand harsh environments using a variety of mechanisms. As a biofilmgrows, interconnected fibers allow its bacteria to function as a larger whole [12]. Within this community certainbacteria develop specific roles. This compartmentalization allows for sharing of nutrients. In addition, quorumsensing is used to communicate between bacteria. This communication stimulates changes in gene expression of nearby bacteria to cope with environmental stresses [12]. Because of this, in a potentially dangerous environmentlike after exposure to antiseptic, genes can be expressed by the biofilm to prevent bacterial death. The adaptability of bacteria in biofilm allows them to survive in stressful conditions.

Because biofilm bacteria can change gene expression, they are especially adept at adapting to their environment. This allows them to not only survive in harsh conditions, but also increase their proliferation in goodconditions. Most bacteria found on human skin are opportunistic pathogens [13]. They cause no harm to us innormal conditions. When the environment changes however, they alter their gene expression and can potentially cause harm. The moist, oxygen dense, and nutrient rich environment surgical sites provide produce the optimalgrowth conditions for biofilms to quickly expand potentially leading to large scale infection. To prevent this opportunistic growth, it is important that biofilms are destroyed prior to the creation of a surgical wound [13].

In order to kill deep skin-dwelling biofilms, antiseptic needs to be present in high enough concentrations forlong enough time to kill the entire biofilm. Traditional PSP scrubs last a few minutes which is not sufficient time forthe antiseptic to reach and kill deeper dwelling bacteria. Transdermal antiseptic products provide a mechanism of sustained antiseptic release over time. These products may vary in composition, but some are hydrocolloids filled with antiseptic [14]. They are commonly used clinically to prevent bacterial growth by maintaining antisepticexposure to bacteria [14]. The three common clinically used transdermal antiseptic products are Tegaderm, Ioban, and Surgiclear. Tegaderm releases CHG over time and is placed over IV insertion points. Ioban releases iodine over time and is placed over the surgical site (after PSP) throughout surgery.

Surgiclear releases CHG over time and is used post-operatively to cover the surgical incision. These products have the potential to significantly reduce skin bacterial levels if the proper compositions and method of use can be determined.

Reduction of skin bacterial levels is necessary to reduce the risk of surgical site infections. This includes bacteria in the deeper areas of the skin that remain even after traditional presurgical preparation methods[6]. By lowering the risk of infection, individuals have a greater chance of positive surgical outcomes without the morbidity, financial, and time burdens associated with infection.

References

[1]               S. Sabbatani, F. Catena, L. Ansaloni, M. Sartelli, B. De Simone, F. Coccolini, S. Di Saverio, and A. Biondi, “The Long and Dramatic History of Surgical Infections”, Arch.Med., vol. 8, no. 6, 2016.

[2]               K. Ban, J. Minei, C. Laronga, B. Harbrecht, E. Jensen, D. Fry, K. Itani, P. Dellinger, C. Ko, and T. Duane, “Executive summary of the American College of Surgeons/Surgical Infection Society Surgical Site Infection Guidelines – 2016 update”, Surg. Infect., vol. 18, no. 5, 2017.

[3]               Medcom, Cypress, CA. Surgical Hand Scrub: Alcohol Based Disinfectant Cleansers, (2010), Accessed: Feb 15, 2024. [Online video]. Available: https://video.alexanderstreet.com/watch/surgical-hand-scrub-alcohol-based-disinfectant-cleansers?utm_campaign=Video&utm_medium=MARC&utm_source=aspresolver

[4]               Medcom, Cypress, CA. Principles of Sterile Technique: Causes of Surgically-Introduced Infection , (2010), Accessed: Feb 15, 2024. [Online video]. Available: https://video.alexanderstreet.com/watch/principles-of-sterile-technique-causes-of-surgically-introduced-infection?utm_campaign=Video&utm_medium=MARC&utm_source=aspresolver

[5]               D. Williams, “Preventing biofilm implant-related osteomyelitis using a novel synthetic analog of antimicrobial peptides”, 2012.

[6]               M. Mastrocola, G. Matziolis, S. Bohle, C. Lindemann, P. Schlattmann, H. Eijer, “Meta-analysis of the efficacy of preoperative skin preparation with alcoholic chlorohexidine compared to povidone iodine in orthopedicsurgery”, Sci. reports, vol. 11, 2021.

[7]               J. Shephard, W. Ward, A. Milstone, T. Carlson, J. Frederick, E. Hadhazy, and T. Perl, “Financial Impact of Surgical Site Infections on Hospitals”, JAMA Surg., vol. 148, no. 10, 2013.

[8]               D. Updegreaff, “A Cultural Method of Quantitatively Studying the Microorganisms in the Skin”, J. Dermatol., vol. 43, no. 2, 1964.

[9]               H. Duffy, R. Godfrey, D. Williams, and N. Ashton, “A Porcine Model for the Development and Testing of Preoperative Skin Preparations”, Microorganisms, vol. 10, no. 5, 2022.

[10]               A. Byrd, Y. Belkaid, and J. Segre, “The human skin microbiome”, Nat. Rev. Microbiol., vol. 16, no. 3, 2018.

[11]               M. Taha, M. Kalab, Q. Yi, C. Landry, V. Greco-Stewart, A. K. Brassinga, C. D. Sifri, S. Ramirez- Arcos, “Biofilm-forming skin microflora bacteria are resistant to the bactericidal action of disinfectants used during blood donation”, Transfus., vol. 54, no. 11, 2014.

[12]               D. G. Anderson, Nesters Microbiology: A Human Perspective, 10th Edition. United States: McGraw-Hill Higher Education, 2021, 92-93.

[13]               K. Vijayakumar, T. Ramanathan, T. Gunasekaran, “Anti-quorum sensing and antibiofilm potential of 1,8-cineole derived from Musa paradisiaca against Pseudomonas aeruginosa strain PAO1”,J. Microbiol. Biotechnol., vol. 37, no. 4, 2021.