Pathogenesis Of Surgical Site Infections Research Articles

This Month in Anesthesiology

This Month in Anesthesiology

Emerging Paradigms in the Prevention of Surgical Site Infection: The Patient Microbiome and Antimicrobial Resistance.

This article summarizes new scientific evidence on the pathogenesis of surgical site infection, including the roles of the patient microbiome and antimicrobial resistance, and reviews changes in guidelines and clinical practices for prevention.

Time-Dependent Displacement of Commensal Skin Microbes by Pathogens at the Site of Colorectal Surgery.

Although the healthy human skin microbiome has been the subject of recent studies, it is not known whether alterations among commensal microbes contribute to surgical site infections (SSIs). Our objective in this study was to characterize temporal and spatial variation in the skin microbiota of patients undergoing colorectal surgery and determine if dysbiosis contributes to SSIs. Sixty one adults scheduled to undergo elective colon or rectal resection were identified by convenience sampling. By analyzing bacterial 16S rRNA gene sequences isolated from clinical samples, we used a culture-independent strategy to monitor perioperative changes in microbial diversity of fecal samples and the skin. A total of 990 samples from 61 patients were analyzed. Alpha diversity on the skin decreased after surgery but later recovered at the postoperative clinic visit. In most patients, we observed a transient postoperative loss of skin commensals (Corynebacterium and Propionibacterium) at the surgical site, which were replaced by potential pathogens and intestinal anaerobes (eg, Enterobacteriaceae). These changes were not observed on skin that was uninvolved in the surgical incision (chest wall). One patient developed a wound infection. Incisional skin swabs from this patient demonstrated a sharp postoperative increase in the abundance of Enterococcus, which was also cultured from wound drainage. We observed reproducible perioperative changes in the skin microbiome following surgery. The low incidence of SSIs in this cohort precluded analysis of associations between dysbiosis and infection. We postulate that real-time monitoring of the skin microbiome could provide actionable findings about the pathogenesis of SSIs.

Airborne particle dispersion around the feet of surgical staff while walking in and out of a bio-clean operating theatre

Bacterial contamination by airborne particles is one of the most important factors in the pathogenesis of surgical-site infections. This study aimed to identify the generation and behaviour of airborne particles around the feet of surgical staff while walking in and out of an operating theatre. Two physicians and two nurses walked in and out of a bio-clean theatre under laminar airflow, either individually or as a group. The generation and behaviour of airborne particles was filmed using a fine-particle visualization system, and the number of airborne particles per 2.83 m3 of air was counted using a laser particle counter. Each action was repeated five times, and particle counts were evaluated statistically. Airborne particles were generated from the floor and by the shoes and gown hems of the participants, whether walking individually or as a group. Numerous airborne particles were generated by the group, and significantly more particles, especially those measuring 0.3-0.5 μm, were carried up to the level of the operating table by the group than by individuals (P<0.01). The results of this study provide a clearer picture of the dispersion and distribution of airborne particles around the feet of staff walking in and out of an operating theatre. The findings suggest that to reduce the incidence of bacterial contamination and risk of surgical site infections, surgical staff should walk calmly and independently, if possible, near sterile areas.

A Systematic Review, Meta-Analysis, and Meta-Regression Evaluating the Efficacy and Mechanisms of Action of Probiotics and Synbiotics in the Prevention of Surgical Site Infections and Surgery-Related Complications.

Intestinal microbiota play an important role in the pathogenesis of surgical site infections (SSIs) and other surgery-related complications (SRCs). Probiotics and synbiotics were found to lower the risk of surgical infections and other surgery-related adverse events. We systematically reviewed the approach based on the administration of probiotics and synbiotics to diminish SSIs/SRCs rates in patients undergoing various surgical treatments and to determine the mechanisms responsible for their effectiveness. A systematic literature search in PubMed/MEDLINE/Cochrane Central Register of Controlled Trials from the inception of databases to June 2018 for trials in patients undergoing surgery supplemented with pre/pro/synbiotics and randomized to the intervention versus placebo/no treatment and reporting on primarily: (i) putative mechanisms of probiotic/symbiotic action, and secondarily (ii) SSIs and SRCs outcomes. Random-effect model meta-analysis and meta-regression analysis of outcomes was done. Thirty-five trials comprising 3028 adult patients were included; interventions were probiotics (n = 16) and synbiotics (n = 19 trials). We found that C-reactive protein (CRP) and Interleukin-6 (IL-6) were significantly decreased (SMD: −0.40, 95% CI [−0.79, −0.02], p = 0.041; SMD: −0.41, 95% CI [−0.70, −0.02], p = 0.006, respectively) while concentration of acetic, butyric, and propionic acids were elevated in patients supplemented with probiotics (SMD: 1.78, 95% CI [0.80, 2.76], p = 0.0004; SMD: 0.67, 95% CI [0.37, −0.97], p = 0.00001; SMD: 0.46, 95% CI [0.18, 0.73], p = 0.001, respectively). Meta-analysis confirmed that pro- and synbiotics supplementation was associated with significant reduction in the incidence of SRCs including abdominal distention, diarrhea, pneumonia, sepsis, surgery site infection (including superficial incisional), and urinary tract infection, as well as the duration of antibiotic therapy, duration of postoperative pyrexia, time of fluid introduction, solid diet, and duration of hospital stay (p < 0.05). Probiotics and synbiotics administration counteract SSIs/SRCs via modulating gut-immune response and production of short chain fatty acids.

Infections complicating cesarean delivery.

Cesarean sections are common surgical procedures performed in a healthy population and are unique because of a relatively high rate of postoperative infection. There have been many important advances in understanding the pathogenesis of infection and evaluation of interventions to prevent post cesarean section infections in the last few years. Our purpose in this review is to analyze these new data, discuss unanswered questions, and propose changes in standard of care. Wound closure techniques including subcuticular sutures and subcutaneous suturing have been shown to be effective at reducing surgical site infections. Wound dressings including negative pressure dressings likely do not decrease infection rates. The type, timing, and duration of preoperative prophylactic antibiotics, including adjunctive azithromycin for laboring women and multidose antibiotics in obese women, have also yielded mixed results. Our understanding of normal uterine microbiome and the impact of intrapartum antibiotics on the newborn is emerging. The pathogenesis of surgical site infections after Cesarean section is complex and multifactorial. Many interventions to reduce infections have been studied with varying degrees of effectiveness. Despite advances in the area, important questions remain unanswered.

A prospective study on various factors influencing post-operative wound infection in emergency surgeries

BackgroundThe risk of surgical site infection (SSI) is approximately 1–3% for elective surgery and more for emergency surgeries. Apart from patient endogenous factors, the role of external risk factors in the pathogenesis of SSI is well recognized. However, among the various measures to prevent SSI, only some are based on strong evidence, and there is insufficient evidence to show whether one method is superior to any other. Therefore, this study was carried out to find out the various factors causing post-operative wound infection, the commonly associated microorganisms, and antibiotic sensitivity and resistance pattern. MethodsThe study was conducted in tertiary care hospital, Pondicherry between September 2012 and September 2014. All the patients who underwent emergency surgeries in the Department of General Surgery were included in the study. An elaborative clinical study of post-operative wound infection was conducted. The suture site was inspected for any sign of infection starting from the second post-operative day till discharge from hospital. Wound swabs were collected and sent for aerobic culture and sensitivity. ResultsIn this study, open appendectomy was the most common surgery that was performed on an emergency basis. Anemia followed by hypoalbuminemia were the two important comorbid conditions. The rate of infection for clean-contaminated, contaminated, and dirty wound were 16.88%, 38%, and 20% respectively. ConclusionSSI occupies a significant proportion among various hospital-acquired infections. SSI not only prolongs the hospitalization but also markedly increases the expenditure and morbidity.

Surgical site infections in dermatologic surgery: etiology, pathogenesis, and current preventative measures.

Surgical site infections (SSIs) after dermatologic surgery continue to represent undesirable complications that affect patients in several aspects. The etiology and pathogenesis of SSIs are not completely understood, and as a result, current preventative measures are debatable. To review and summarize the current available literature specific to SSIs in dermatologic surgery. The pathogenesis of SSIs, factors contributing to SSIs, current preventative guidelines, and evidence supporting their use are explored. A review of the medical literature. Most measures used to prevent SSIs in dermatologic surgery are based on studies of wounds in general surgery. Evidence specific to dermatologic surgery is scarce. More research related to the pathogenesis of SSIs is needed to establish effective preventative measures that are key to reducing incidences of SSIs.

Using an Agent-Based Model to Examine the Role of Dynamic Bacterial Virulence Potential in the Pathogenesis of Surgical Site Infection

Despite clinical advances, surgical site infections (SSIs) remain a problem. The development of SSIs involves a complex interplay between the cellular and molecular mechanisms of wound healing and contaminating bacteria, and here, we utilize an agent-based model (ABM) to investigate the role of bacterial virulence potential in the pathogenesis of SSI. The Muscle Wound ABM (MWABM) incorporates muscle cells, neutrophils, macrophages, myoblasts, abstracted blood vessels, and avirulent/virulent bacteria to simulate the pathogenesis of SSIs. Simulated bacteria with virulence potential can mutate to possess resistance to reactive oxygen species and increased invasiveness. Simulated experiments (t=7 days) involved parameter sweeps of initial wound size to identify transition zones between healed and nonhealed wounds/SSIs, and to evaluate the effect of avirulent/virulent bacteria. The MWABM reproduced the dynamics of normal successful healing, including a transition zone in initial wound size beyond which healing was significantly impaired. Parameter sweeps with avirulent bacteria demonstrated that smaller wound sizes were associated with healing failure. This effect was even more pronounced with the addition of virulence potential to the contaminating bacteria. The MWABM integrates the myriad factors involved in the healing of a normal wound and the pathogenesis of SSIs. This type of model can serve as a useful framework into which more detailed mechanistic knowledge can be embedded. Future work will involve more comprehensive representation of host factors, and especially the ability of those host factors to activate virulence potential in the microbes involved.

Examination of the Effect of Host-microbe Dynamics on Bacterial Virulence Activation in the Pathogenesis of Surgical Site Infection Using an Agent-based Model

Examination of the Effect of Host-microbe Dynamics on Bacterial Virulence Activation in the Pathogenesis of Surgical Site Infection Using an Agent-based Model

Risk Factors for Postoperative Infection Following Posterior Lumbar Instrumented Arthrodesis

Surgical site infection in the spine is a serious postoperative complication. Factors such as posterior surgical approach, arthrodesis, use of spinal instrumentation, age, obesity, diabetes, tobacco use, operating-room environment, and estimated blood loss are well established in the literature to affect the risk of infection. The goal of this study was to analyze and identify independent risk factors for surgical site infection among spine patients undergoing posterior lumbar instrumented arthrodesis. The medical records of 3218 patients who underwent posterior lumbar instrumented arthrodesis from January 2000 to December 2006 were reviewed to identify those who developed a postoperative infection (eighty-four patients; 2.6%). The size of this single-institution patient group allowed construction of a multivariate logistic regression model to evaluate the independent associations of potential risk factors for surgical site infection in the spine. In the final regression model, obesity, estimated intraoperative blood loss, ten or more people in the operating room, a dural tear, history of diabetes, chronic obstructive pulmonary disease, coronary heart disease, and osteoporosis were critical risk factors for the onset of spinal surgical site infection. Obesity and a history of chronic obstructive pulmonary disease were the strongest risk factors for postoperative spinal infection after adjusting for all other variables. The most common pathogen was methicillin-resistant Staphylococcus aureus with a prevalence of 34.5%. This study established a single institution infection rate for posterior lumbar instrumented arthrodesis at 2.6%. This analysis confirms previously demonstrated risk factors for postoperative infection while reporting on new potential independent risk factors of osteoporosis, chronic obstructive pulmonary disease, and dural tears in the setting of posterior lumbar instrumented arthrodesis. Areas of new research can focus on the roles these novel factors may play in the pathogenesis of surgical site infections in the spine.

Clinical significance of positive cranial bone flap cultures and associated risk of surgical site infection after craniotomies or craniectomies

The risk of surgical site infection (SSI) after craniotomies or craniectomies in patients in whom contaminated bone flaps have been reimplanted has not been determined. The objectives of this study were to identify the prevalence of bone flaps with positive cultures--especially those contaminated with Propionibacterium acnes--to assess the risk of SSI after reimplanting (either during the initial operation or subsequently) bone flaps with positive cultures, and to identify risk factors for SSI following the initial craniotomies or craniectomies. The authors conducted a retrospective review of cases in which patients underwent craniotomy/craniectomy procedures between January and October 2007 in the neurosurgery department at the University of Iowa Hospitals and Clinics. They also reviewed processes and procedures and did pulsed field gel electrophoresis of P. acnes isolates to look for a common source of contamination. They then conducted a prospective cohort study that included all patients who underwent craniotomy/craniectomy procedures between November 2007 and November 2008 and met the study criteria. For the cohort study, the authors obtained cultures from each patient's bone flap during the craniotomy/craniectomy procedures. Data about potential risk factors were collected by circulating nurses during the procedures or by a research assistant who reviewed medical records after the procedures. An infection preventionist independently identified SSIs through routine surveillance using the Centers for Disease Control and Prevention's definitions. Univariate and bivariate analyses were performed to determine the association between SSI and potential risk factors. The retrospective review did not identify specific breaks in aseptic technique or a common source of P. acnes. Three hundred seventy-three patients underwent 393 craniotomy/craniectomy procedures during the cohort study period, of which 377 procedures met the study criteria. Fifty percent of the bone flaps were contaminated by microorganisms, primarily skin flora such as P. acnes, coagulase-negative staphylococci, and Staphylococcus aureus. Reimplanting bone flaps that had positive culture results did not increase the risk of infection after the initial craniotomy/craniectomy procedures and the subsequent cranioplasty procedures (p = 0.80). Allowing the skin antiseptic to dry before the procedures (p = 0.04, OR 0.26) was associated with lower risk of SSIs. Female sex (p = 0.02, OR = 3.49) was associated with an increased risk of SSIs; Gliadel wafer implants (p = 0.001, OR = 8.38) were associated with an increased risk of SSIs after procedures to treat tumors. Operative factors such as the way the skin is prepared before the incision rather than the skin flora contaminants on the bone flaps may play an important role in the pathogenesis of SSIs after craniotomy/craniectomy. Gliadel wafers significantly increased the risk of SSI after procedures to treat tumors.

Preventing surgical site infections

The risk of surgical site infection (SSI) is approximately 1–3% for elective clean surgery. Apart from patient endogenous factors, the role of external risk factors in the pathogenesis of SSI is well recognized. However, among the many measures to prevent SSI, only some are based on strong evidence, for example, adequate perioperative administration of prophylactic antibiotics, and there is insufficient evidence to show whether one method is superior to any other. This highlights the need for a multimodal approach involving active post-discharge surveillance, as well as measures at every step of the care process, ranging from the operating theater to postoperative care. Multicenter or supranational intervention programs based on evidence-based guidelines, ‘bundles’ or safety checklists are likely to be beneficial on a global scale. Although theoretically reducible to zero, the maximal realistic extent by which SSI can be decreased remains unknown.

Minimizing the risk of postoperative infection

ABSTRACTSurgical site infections occur in approximately 2.6% of the patient population, causing considerable discomfort and expense. We review the microbiology and pathogenesis of surgical site infections and identify the most common risk factors in patients. Steps to reduce infection can be taken i

Antimicrobial Susceptibility Pattern of Microorganisms Involved in the Pathogenesis of Surgical Site Infection (SSI); A 1 Year of Surveillance

The aim of this study is to identify the antibiotic sensitivity pattern of pathogens involved in the process of surgical site infection, in surgical wards. Changes made in the pattern of antibiotic use will result in different microorganism susceptibility patterns, which needs correct determination for precise empiric antibiotic therapy. One thousand patients (62% men and 38% women, 18- 74-years-old, with mean age 43 +/- 8)) who underwent surgical treatment, in Alzahra University Hospital, Isfahan University of Medicine, Isfahan, Iran, were studied from 2005 to 2006. Surgical wound infections, based on the reported criteria, were aspirated for culturing within 1 plus gram staining of prepared smears. Minimum Inhibitory Concentrations (MICs) were determined for samples and all derived data were compared by SPSS 13 and WHO net 5 software. The prevalence of SSI was 13.3% with 150 positive cultures, totally. Of 150 bacteria, isolated from surgical site infections Staphylococcus aureus had most frequency (43%). Resistance of isolated organisms was 41.7% in amikacin, 65 and 78.6% in ceftazidime, 85.7% in ceftriaxone, 61.5% in ciprofloxacin, 78.8% in gentamicine, 6.4% in imipenem, 13% in meropenem and 70.6% in trimethoprim/sulfamethoxazole, respectively. 78.9% of Staphylococcus aureus isolates were MRSA and vancomycine was the most effective antibiotic without any resistance. Among 10 isolates of coagulase negative Staphylococcus, no vancomycine resistance was seen, but in contrast all cases were resistant to oxacillin. The most common gram negative organism was Klebsiella (18 isolates) in which 100 and 80% were sensitive to imipenem and meropenem, respectively. Seventeen cases were E. coli, in which the most sensitivity was to meropenem (80%) and imipenem (77.8%). Thirteen cases of Pseudomonas were detected, in which 16.7% were resistant to imipenem and 8.3% to meropenem. Our results demonstrated that the total antibiotic resistance is increasing among SSIs, with an up sloping pattern, which will contact with a constant empiric antibiotic therapy. So, precise up to date antibiogram tantalize us toward balancing the rate of total antibiotic resistance to SSIs.

Prevention of sternal wound infections with locally administered gentamicin

Despite modern surgical techniques and our knowledge of the pathogenesis of surgical site infections (SSIs) and the use of perioperative antibiotic prophylaxis, the incidence of SSIs has not decreased, but has remained at the same level. More effective preventive methods are thus needed and will likely become even more important in the future due to older and sicker patients, the population becoming increasingly obese, type II diabetes becoming more common, and the emergence of resistant bacteria. The use of local antimicrobial prophylaxis was studied. The study population comprised 557 patients who underwent elective CABG. The patients were randomized and patients in the study group received a 10 cm x 10 cm gentamicin-collagen implant. Postoperative SSI occurred in 11 of 272 patients (4.0%) in the study group and in 16 of 270 patients (5.9%) in the control group. This difference was not statistically significant (P=0.20). There were three cases of mediastinitis (1.1%) in the study group and five (1.9%) in the control group (P=0.47).

Fulminant infection of the lower limb in a diabetic patient

The pathogenesis of surgical site infection (SSI) involves the complicated inter action of many risk factors, each of which has a different impact on the local tissue status. Risk factors responsible for SSIs are classified as definitive, probable or possible. Diabetes mellitus is classified as an important ‘probable’ risk factor that can be overcome with therapeutic control of glycaemic imbalance. A significant correlation has been found between higher levels of glycated haemoglobin A1C (HBA1C) and SSI frequency in patients undergoing coronary artery bypass surgery, while a significant increase in SSI morbidity was noted in diabetic patients compared with non-diabetic patients.

Perioperative blood transfusion is predictive of poststernotomy surgical site infection: marker for morbidity or true immunosuppressant?

To analyze risk factors for the development of adult poststernotomy surgical site infections (SSIs), we performed a retrospective case-control study at a tertiary care hospital. Case patients with poststernotomy SSI between June 1999 and January 2001 were matched to control subjects without poststernotomy SSI according to date of procedure and age. Data were collected on known SSI risk factors. Of 711 procedures, we identified 38 cases with SSI and 114 matched controls. Univariate analysis revealed that receipt of transfused blood (odds ratio [OR], 3.19; 95% confidence interval [CI], 1.54-6.62), diabetes (OR, 2.90; 95% CI, 1.27-6.59), length of stay before hospitalization (OR, 1.19 per day; 95% CI, 1.02-1.37 per day), and American Society of Anesthesia score (OR, 2.19; 95% CI, 1.04-4.64) were significantly associated with SSI. Multivariate analysis revealed that transfusion (OR, 3.21; 95% CI, 1.41-7.31) and diabetes (OR, 3.65; 95% CI, 1.42-9.36) were predictors for SSI. The exact role of blood transfusion in the pathogenesis of SSI, whether as a direct immunosuppressant or a surrogate marker for morbidity, remains unresolved.