Prevention of surgical site infections: Where do we stand today?

Surgical site infections (SSIs) are infections related to operative procedures, that occur within 30 or 90 days of the intervention. They constitute a significant burden on healthcare-associated infections.[1] SSIs commonly localise around the incision site, but they can penetrate deeper adjacent structures. While global estimates of SSI prevalence range from 0.5% to 15%, studies conducted in India consistently report higher rates, ranging from 23% to 38%. The incidence of SSIs is influenced by various factors, including the type of wounds and the location of the operative intervention, with cardiovascular and gastrointestinal surgeries being particularly prone to SSIs.[2-4] Patient-related factors such as older age, immunosuppression, obesity and uncontrolled diabetes predispose to an increase in SSIs. MICROBIOLOGY After a clean procedure, the patient's skin flora organisms (streptococcal, Staphylococcus aureus and coagulase-negative staphylococcus) are responsible for the occurrence of SSIs. In clean-contaminated procedures, such as gastrointestinal surgeries, gram-negative rods and enterococci become predominant alongside normal skin flora. When the surgical procedure involves a viscus, the pathogens typically reflect the endogenous flora of the viscus or nearby mucosal surfaces, resulting in polymicrobial infections. S. aureus has emerged as the most common cause of SSIs globally. While methicillin-resistant S. aureus (MRSA) historically posed a greater risk of SSIs than methicillin-sensitive S. aureus (MSSA), recent trends show an increase in MSSA-derived SSIs. However, MRSA SSIs are still associated with higher mortality rates, prolonged hospital stays and increased costs. SSI outbreaks have been reported in various operating rooms, with Group A streptococci carriage in the anal, vaginal or nasopharyngeal areas of operating room personnel implicated as a potential cause of several outbreaks. Rarely, outbreaks or clusters of SSIs caused by unusual pathogens such as non-tuberculous mycobacteria have been linked to contaminated dressings, bandages, irrigants or disinfection solutions. An increasing percentage of SSIs has been caused by fungi, particularly Candida albicans. This trend is likely due to the widespread use of prophylactic and empirical antibiotics, the increased severity of illnesses and the growing number of immunocompromised patients undergoing surgical procedures. In addition, Cutibacterium acnes is commonly isolated in post-operative infections following shoulder surgery. CLINICAL FEATURES An SSI is suspected when there is either new or persistent purulent drainage at the incision site or evidence of an abscess affecting the surgical bed. Physical examination findings typically include systemic signs of infection, such as fevers and rigours, along with local signs, such as erythema, wound dehiscence, pain, non-purulent drainage or induration. These manifestations are present in the majority of cases of suspected SSIs. ANTIMICROBIAL PROPHYLAXIS The primary objective of antimicrobial prophylaxis is to prevent SSIs by reducing the microbial burden at the surgical site during the operative procedure. It is important to note that antimicrobial therapy administered in the context of contaminated or dirty wounds or procedures is not considered prophylactic; in such cases, a therapeutic course of antimicrobial therapy is warranted. In an ideal setting, antimicrobial prophylaxis should meet several objectives: preventing SSIs, reducing morbidity and mortality, shortening healthcare duration and cost, causing minimal adverse drug effects and, in addition, having minimal impact on the patient's or hospital's microbial flora. To achieve these goals, the antimicrobial agent must be effective against the pathogens most likely to contaminate the surgical site. It should be administered at the correct dose and timing to ensure adequate serum and tissue concentrations, ideally within 60 min before the surgical incision. The antibiotic's half-life should also be considered, especially for drugs requiring prolonged infusions, such as vancomycin or fluoroquinolones, which should be started 120 min before the surgical incision. Typically, a single prophylactic dose is sufficient to prevent SSI. However, repeat intraoperative dosing may be necessary, especially for procedures exceeding two half-lives of the drug, surgeries with significant blood loss (>1500 mL) or patients with extensive burns where drug absorption may be compromised. In cases of renal impairment, dose modification may be necessary, but redosing is generally not recommended. Cefazolin is the most extensively studied antimicrobial agent, with proven effectiveness for surgical prophylaxis. It has a broad spectrum of activity against organisms commonly encountered in surgery, including streptococci, methicillin-susceptible staphylococci and many gram-negative organisms. In addition, cefazolin is known for its reliable safety profile and cost-effectiveness. Cefuroxime, a second-generation cephalosporin, theoretically provides broader coverage against gram-negative organisms than cefazolin. However, resistance to these antimicrobials is increasing. Alternatives to cephalosporins include intravenous vancomycin (15–20 mg/kg) or clindamycin (600–900 mg). Additional antibiotic options, such as cefazolin plus metronidazole, cefoxitin or ertapenem, may be considered based on specific surgical sites, hospital-specific protocols and patient-specific antibiotic resistance patterns. Is there a role for pre-operative Staphylococcus aureus decolonisation? The optimal strategy for screening and decolonising S. aureus remains uncertain, as evidenced by varied results across multiple studies. Pre-operative decolonisation has demonstrated benefits primarily for patients undergoing orthopaedic or cardiac procedures. However, universal pre-operative S. aureus decolonisation is no longer recommended for several reasons. One significant concern is that universal nares screening may fail to identify up to 20% of patients with S. aureus colonisation. In addition, there is a lack of standardised decolonisation regimens, which complicates the implementation of universal decolonisation protocols. Another issue is the emergence of resistance to mupirocin, an antibiotic commonly used for decolonisation, amongst S. aureus strains due to indiscriminate use. Given these challenges and uncertainties, the widespread adoption of universal pre-operative S. aureus decolonisation is no longer recommended. Instead, decolonisation strategies should be tailored to specific patient populations and procedures, with careful consideration of the risks and benefits. Is dual antibiotic coverage better than monotherapy for SSI prevention? Monotherapy has been the backbone for preventing SSIs. Recent evidence is emerging that the upfront use of dual antibiotics has some added benefits. In a study by Sewick et al. (2012), a retrospective analysis was performed on 1828 primary total hip arthroplasties and total knee arthroplasties carried out between 1st September 2008, and 31st December 2010. Patients were divided into two groups: one received a dual prophylactic antibiotic regimen of cefazolin and vancomycin (unless allergic), whereas the other received cefazolin alone (unless allergic). The follow-up period was extended to 1 year, assuming subsequent infections were unrelated to the initial surgery. During this timeframe, 22 SSIs occurred, resulting in an infection rate of 1.2%. The study found that adding vancomycin as a prophylactic antibiotic did not significantly reduce the rate of SSIs compared to cefazolin alone.[5] In another study conducted by Bains et al., 2907 patients who underwent primary total joint arthroplasty between 1st January 2014, and 31st May 2021, were included. These patients were divided into two groups: one received cefazolin and vancomycin, whereas the other received cefazolin only. The study examined SSIs and periprosthetic joint infections (PJIs) over 1 year and determined microbial culture rates. The results indicated no significant difference in the rates of SSIs or PJIs between the two groups 1 year after surgery. However, adding vancomycin resulted in a more substantial reduction in MRSA amongst patients previously screened through nasal swabs. Consequently, the study concluded that adjunctive vancomycin therapy provided increased protection against MRSA in previously screened individuals but not in those negative for pre-operative MRSA screening, suggesting that routine use of vancomycin prophylaxis may not be necessary.[6] Similar findings were reported in a study conducted by Berman et al., which involved 184 patients undergoing cardiac surgery requiring pre-operative antibiotic prophylaxis. Patients were divided into two groups: one received vancomycin with a cephalosporin, and the other received a cephalosporin alone. The study found no significant difference in the incidence of surgical wound infections between the two groups within 30 days of surgery. In addition, there were no significant differences in secondary outcomes such as 30-day mortality, readmission or reoperation rates. Although the incidence of acute kidney injury was numerically higher in the combination therapy group, this difference was not statistically significant.[7] CONCLUSION The current evidence does not strongly support using dual antibiotics as a pre-operative or procedural prophylaxis.