Surgical Site Infections in Orthopaedic Surgery Demonstrate Clones Similar to Those in Orthopaedic Staphylococcus aureus Nasal Carriers

Staphylococcus aureus colonization and surgical site infections among patients undergoing surgical fixation for acute fractures

OBJECTIVES

To identify risk factors for methicillin-susceptible (MSSA) and methicillin-resistant S. aureus (MRSA) nasal carriage and surgical site infection (SSI) among patients undergoing fracture fixation procedures who were included in a quality improvement protocol involving screening patients for S. aureus nasal carriage and treating carriers with intranasal mupirocin and chlorhexidine bathing.

DESIGN

Retrospective cohort study.

SETTING

Level 1 trauma center.

PARTICIPANTS

1,254 adults who underwent operative fixation of 1,298 extremity or pelvis fractures between 8/1/2014 - 7/31/2017.

METHODS

We calculated rates of S. aureus nasal carriage and SSI. We used multivariable stepwise logistic regression and selected the final models based on Akaike information criterion.

RESULTS

Of the 1,040 screened first procedures, 262 (25.19%) were performed on S. aureus nasal carriers: 211 (20.29%) on MSSA carriers and 51 (4.90%) on MRSA carriers. Long-term care facility residence (odds ratio [OR] 3.38; 95% confidence interval [CI] 1.17-9.76) was associated with MRSA nasal carriage. After adjusting for statistically and clinically significant variables, MRSA carriage was significantly associated with any SSI (OR 4.58; 95% CI 1.63-12.88), S. aureus SSI (OR 10.11; 95% CI 3.25-31.42), and MRSA SSI (OR 27.25; 95% CI 5.33-139.24), whereas MSSA carriage was not. Among S. aureus carriers, any chlorhexidine use was documented for 232 (88.55%), and any intranasal mupirocin was documented for 85 (40.28%) MSSA carriers and 33 (64.71%) MRSA carriers.

CONCLUSIONS

MRSA carriage was associated with a significant risk of SSI after operative fracture fixation. Many carriers did not undergo decolonization, suggesting that a simplified decolonization protocol is needed.

Preoperative MRSA screening using a simple questionnaire prior elective total joint replacement

INTRODUCTION

The purpose of this study was to evaluate the management and results of our standarized protocol for preoperative identification of MRSA colonisation in patients undergoing primary total hip and knee replacement procedures.

METHODS

Following hospital protocol, between January 2016 and June 2019 37,745 patients awaiting elective joint replacement underwent a standardized questionnaire to assess the risk of MRSA infection, identifying patients requiring preoperative MRSA screening. An evaluation of the questionnaire identified effective questions for identifying infected patients. Furthermore, an analysis evaluated the impact of comorbidities or Charlson Comorbidity Index scores on positive MRSA colonization. Additionally, we evaluated the cost savings of targeted testing compared to testing all surgery patients.

RESULTS

Of the 37,745 patients, 8.057 (21.3%) were swabbed, with a total of 65 (0.81%) positive tests. From this group 27 (36.48%) who were treated were negative before surgery. Some of the questionnaire results were consistently associated with a higher chance of colonization, including hospitalization during the past year (47,7%), previous history of MRSA (44,6%), and agriculture or cattle farming related work (15,4%). By selectively testing high-risk patients identified through the questionnaire, we achieved a 79% reduction in costs compared to universal MRSA screening.

CONCLUSION

Our results suggest that the simple and standardized questionnaire is a valuable tool for preoperative screening, effectively identifying high-risk patients prone to MRSA colonisation. The risk of periprosthetic joint infection (PJI) and its associated sequelae may be reduced by this approach.

Cutting Periprosthetic Infection Rate: Staphylococcus aureus Decolonization as a Mandatory Procedure in Preoperative Knee and Hip Replacement Care-Insights from a Systematic Review and Meta-Analysis of More Than 50,000 Patients

Background: No consensus in the literature has been found about the necessity of implementing a decolonization screening protocol for Staphylococcus aureus in patients who undergo prosthesis implantation of the knee (TKA) or of the hip (THA), with the aim of reducing periprosthetic infections (PJIs). Methods: A systematic literature search was conducted using PubMed, Web of Science, and Embase in April 2024. Studies conducted on patients who underwent a TKA or THA and who followed a screening and decolonization protocol from S. aureus were included. The benefits of implementing this protocol were evaluated through the number of infections overall caused by S. aureus and other pathogens. The risk of bias and quality of evidence were assessed using Cochrane guidelines. Results: A total of 922 articles were evaluated, and of these, 12 were included in the study for a total of 56,930 patients. The results of the meta-analysis showed a reduced risk of overall PJI (p = 0.002), PJI caused by S. aureus (p < 0.0001), and PJI caused by MRSA (p < 0.0001) and highlighted no differences between the two groups in the onset of a PJI caused by other bacteria (p = 0.50). Conclusions: This study showed that the screening and decolonization of S. aureus in patients undergoing THA or THA procedures reduced the risk of a PJI. The screening and decolonization protocol for this kind of patient represents an important procedure for the safety of the patient and in social-economic and medico-legal terms.

Contribution of the patient microbiome to surgical site infection and antibiotic prophylaxis failure in spine surgery

Despite modern antiseptic techniques, surgical site infection (SSI) remains a leading complication of surgery. However, the origins of SSI and the high rates of antimicrobial resistance observed in these infections are poorly understood. Using instrumented spine surgery as a model of clean (class I) skin incision, we prospectively sampled preoperative microbiomes and postoperative SSI isolates in a cohort of 204 patients. Combining multiple forms of genomic analysis, we correlated the identity, anatomic distribution, and antimicrobial resistance profiles of SSI pathogens with those of preoperative strains obtained from the patient skin microbiome. We found that 86% of SSIs, comprising a broad range of bacterial species, originated endogenously from preoperative strains, with no evidence of common source infection among a superset of 1610 patients. Most SSI isolates (59%) were resistant to the prophylactic antibiotic administered during surgery, and their resistance phenotypes correlated with the patient's preoperative resistome (P = 0.0002). These findings indicate the need for SSI prevention strategies tailored to the preoperative microbiome and resistome present in individual patients.

Increased prevalence of Staphylococcus aureus nasal carriage in rheumatoid arthritis patients with moderate/high disease activity

BACKGROUND

Staphylococcus aureus (S. aureus) nasal carriage is a well-known risk factor for surgical site infection (SSI) after total joint arthroplasty. This study aimed to compare the prevalence of S. aureus nasal carriage between patients with osteoarthritis (OA), a degenerative joint disease, and those with rheumatoid arthritis (RA), a chronic autoimmune inflammatory disease, who underwent total joint arthroplasty, and to investigate the influence of RA disease activity on nasal carriage rate.

METHODS

This retrospective study targeted 508 OA and 107 RA patients who underwent S. aureus nasal screening prior to primary total knee and/or hip arthroplasty. RA patients were divided into two groups based on disease activity: the remission/low disease activity (REM/LDA) group and the moderate/high disease activity (MDA/HDA) group. Factors associated with S. aureus nasal carriage were assessed with multivariate logistic regression models.

RESULTS

Of all 615 patients, 155 (25%) carried S. aureus in their nares. Compared to OA patients, RA patients had a significantly higher rate of S. aureus nasal carriage (24% vs. 33%, p = 0.049). Compared to the REM/LDA group (n = 39), the MDA/HDA group (n = 58) had a significantly higher rate of S. aureus nasal carriage (21% vs. 41%, p = 0.032). Multivariate analysis revealed that the MDA/HDA group, but not the REM/LDA group, had a significantly higher odds of S. aureus nasal carriage compared to the OA group (odds ratio: 2.76, 95% confidence interval: 1.07-7.12).

CONCLUSION

Preoperative nasal screening for S. aureus is beneficial, especially in RA patients with moderate/high disease activity.

A Novel Protocol for Nasal Decolonization Using Prolonged Application of an Alcohol-Based Nasal Antiseptic Reduces Surgical Site Infections in Total Joint Arthroplasty Patients: A Retrospective Cohort Study

Background: Current nasal decolonization strategies utilize pre-operative agents without consideration for short-term re-colonization or de novo colonization. Many strategies utilize an antibiotic-based agent, raising concerns of limited gram-negative antimicrobial coverage and the emergence of resistant bacterial strains. This study evaluated the clinical utility of a non-antibiotic, alcohol-based nasal decolonization agent in decreasing surgical site infection (SSI) rates after total joint arthroplasty. Patients and Methods: We retrospectively compared an 18-month cohort of elective primary total joint arthroplasty patients treated peri-operatively with an alcohol-based sanitizer to historical controls. The alcohol-based agent was administered pre-operatively the day of surgery and for two weeks after surgery. Patients were followed for 90 days and assessed for signs or symptoms of SSI. Patient and caregiver compliance was recorded. There were 779 patients included in the experimental group and 647 included in the historical control group. Results: Patients receiving alcohol-based nasal decolonization had a lower rate of SSI compared with controls not receiving nasal decolonization (0.64% [5/779] vs. 1.55% [10/647]; p = 0.048; odds ratio, 2.43). Utilization of an alcohol-based nasal sanitizer in the pre-operative and prolonged post-operative setting decreased infection rates by 41.3% in our elective total joint arthroplasty setting. Conclusions: When used pre- and post-operatively, alcohol-based nasal decolonization of bacteria in patients undergoing total joint arthroplasty led to a substantial decrease in SSIs.

Severe local wound infections after vascular exposure in the groin and other body areas: Prevention, treatment and prognosis

Severe surgical site infections (SSIs) are a frequent nosocomial complication after vascular interventions, an important cause of postoperative morbidity, and a substantial burden to the health care system. Patients undergoing arterial interventions are at elevated risk of SSIs, possibly because of the presence of several risk factors in this patient population. In this review, we examined the available clinical evidence for the prevention, treatment, and prognostication of postoperative severe SSIs after vascular exposure in the groin and other body areas. Results from studies evaluating preoperative, intraoperative, and postoperative preventive strategies and several treatment options are reviewed. In addition, risk factors for surgical wound infections are analyzed in detail and related evidence from the literature is highlighted. Although several measures have been implemented over the time to prevent them, SSIs continue to pose a substantial health care and socioeconomic challenge. Therefore, strategies to decrease the risk and improve the treatment of SSIs for the high-risk vascular patient population should be the focus of continuing improvement and critical review. This review aimed at identifying and reviewing the current evidence for preventing, treating, and performing stratification according to the prognosis of postoperative severe SSIs after vascular exposure in the groin and other body areas.

Effective screening methods to prevent surgical site infections in orthopedic surgery: an observational study

BACKGROUND

The bacterial source of surgical-site infections (SSIs) can have either endogenous and/or exogenous origins, and some studies have revealed that endogenous transmission is an important pathway for SSIs in orthopedic surgery. However, since the frequency of SSIs is low (0.5-4.7%), screening all surgery patients is labor-intensive and cost-prohibitive. The goal of this study was to better understand how to improve the efficacy of nasal culture screening in preventing SSIs.

METHODS

Nasal cultures for 1616 operative patients over a 3-year period were evaluated for the presence of nasal bacterial microbiota and the species identity. We also investigated the medical factors that influence colonization and evaluated the ratio of agreement between nasal cultures and SSI-causing bacteria.

RESULTS

In a survey of 1616 surgical cases, 1395 (86%) were normal microbiota (NM), 190 (12%) were MSSA carriers, and 31 (2%) were MRSA carriers. The risk factors for MRSA carriers were significantly higher than the NM group in patients with a history of hospitalization (13 [41.9%], p = 0.015), patients who had been admitted to a nursing facility (4 [12.9%], p = 0.005), and patients who were > 75 years of age (19 [61.3%], p = 0.021). The incidence of SSIs was significantly higher in the MSSA group (17/190 [8.4%]) than the NM group (10/1395 [0.7%], p = 0.00). The incidence of SSIs in the MRSA group (1/31 [3.2%]) tended to be higher than that in the NM group, but there was no statistically significant difference (p = 0.114). The concordance rate between causative bacteria of SSI and species present in nasal cultures was 53% (13/25 cases).

CONCLUSIONS

The results of our study suggest screening patients with a history of past hospitalization, a history of admission in a long-term care facility, and older than 75 to reduce SSIs.

TRIAL REGISTRATION

This study was approved by the institutional review board of the authors' affiliated institutions (the ethics committee of Sanmu Medical Center, 2016-02).

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.

Risk factors for preoperative nasal carriage of methicillin-resistant bacteria in total hip and knee arthroplasty patients

BACKGROUND

The present study aimed to identify risk factors for preoperative nasal carriage of resistant bacteria - MRSA methicillin-resistant Staphylococcus (S.) aureus, MRSE (methicillin-resistant Staphylococcus epidermidis), and MRCNS (methicillin-resistant coagulase negative staphylococci) in total hip and knee arthroplasty (THA and TKA) patients.

METHODS

Nasal cultures were obtained from 538 patients before THA (262 primary and 26 revision) and TKA (241 primary and 9 revision). These were classified either as methicillin-resistant bacteria (group MR) or methicillin-susceptible bacteria (including culture-negative) (group MS). Patient characteristics were compared between these groups using logistic regression models.

RESULTS

The resistant bacteria were preoperatively present in 33.1% (178 patients) among all patients. MRSE, MRCNS, and MRSA were detected in 27.5% (148 patients), 3.7% (20 patients), and 1.9% (10 patients). In the unadjusted comparisons of the patient characteristics between the groups MR and MS, a significant difference was found in the percentages of diabetic patients (15.2% vs. 9.2%, P = 0.04); the association remained after the multivariable adjustment for possible risk factors (P < 0.001). In addition, the diabetic patients in the group MR showed a higher percentage of receiving insulin injection than those in the group MS (25.9% vs. 6.1%, P = 0.063), and their mean levels of HbA1c were significantly higher in the group MR than the MS (6.8% vs. 6.4%, P = 0.03).

CONCLUSIONS

We identified diabetes as a risk factor for the preoperative nasal carriage of resistant bacteria. Our results suggest that, in order to prevent a surgical site infection (SSI), extra care should be taken in performing joint arthroplasties for diabetic patients, especially using insulin and with high HbA1c levels (≥6.6%) prior to the surgical procedures.

Staphylococcus aureus genotype variation among and within periprosthetic joint infections

Staphylococcus aureus is a common organism in orthopedic infections, but little is known about the genetic diversity of strains during an infectious process. Using periprosthetic joint infection (PJI) as a model, a prospective study was designed to quantify genetic variation among S. aureus strains both among and within patients. Whole genome sequencing and multilocus sequence typing was performed to genotype these two populations at high resolution. In nasal cultures, 78% of strains were of clonal complexes CC5, CC8, and CC30. In PJI cultures, only 63% could be classified in these common clonal complexes. The PJI cultures had a larger proportion of atypical strains, and these atypical strains were associated with poor host status and compromised immune conditions. Mutations in genes involved in fibronectin binding (ebh, fnbA, clfA, and clfB) systematically distinguished later PJI isolates from the first PJI isolate from each patient. Repeated mutations in S. aureus genes associated with extracellular matrix binding were identified, suggesting adaptive, parallel evolution of S. aureus during the development of PJI.

Screening of MRSA colonization in patients undergoing total joint arthroplasty

Background

Periprosthetic infection is commonly caused by Staphylococcus aureus and, if resistant to methicillin (MRSA), is associated with increase in severity and costs to patient and healthcare systems. MRSA colonizes 1-5% of the population, therefore using a screening and decolonisation protocol the risk of periprosthetic infection could be reduced. The objective of our study is to report the results of a preoperative MRSA screening and management protocol utilised at our hospital.

Methods

All patients undergoing a total joint arthroplasty at our hospital were preoperatively screened for MRSA colonization with swab samples of five different locations. Exposure to risk factors were investigated in colonised patients and they were treated for 5 days prior surgery with nasal mupirocin, chlorhexidine sponges and oral tablets.

Results

During the 48 months of the study, MRSA colonisation was identified in 22 (1.01%) of 2188 patients operated. The culture was positive only in the nasal swab in 55 patients. In five patients the nasal culture was negative, but they had another positive swab culture (three in the groin and two perianal). None of the patients reported a history of recent antibiotic treatment or hospitalization.

Conclusion

At our institution, the prevalence of MRSA colonisation is 1.01% in patients undergoing hip and knee arthroplasty. Interestingly, our screening protocol included samples from five different anatomic locations, and it is important to highlight that we found patients with negative nares culture and positive cultures in other locations. Therefore, the number of carriers may be underdiagnosed if only nasal samples are obtained.

Level of evidence

IV.

Periprosthetic infection risks and predictive value of C-reactive protein / albumin ratio for total joint arthroplasty

BACKGROUND AND AIM

There are no gold standard markers to estimate the risk of developing periprosthetic infections. Our aim is to compare the risks of periprosthetic infection in patients with THA and THA and to investigate the predictive significance of the CRP / albumin ratio.

METHODS

This is a retrospective study containing data from 241 osteoarthritis patients and 19 patients with periprosthetic infections who underwent TKA and THA in our hospital from January 2014 to January 2019.12 risk factors(CRP/ albumin, albumin, CRP, age, gender, BMI, DM, ASA, nasal culture, urine culture, hospital stay, operation time) were analyzed.

RESULTS

In the binary logistic regression model and multivariate regression analysis, the rate of CRP / albumin was 17.161 times higher than the patients with ≤0.16 cut-off value. (CRP / albumin ratio (odds ratio (OR) = 17.16, 95% CI: 1.55-189.03, P: 0.02). High BMI increased the risk of periprosthetic infection 1.3 times. Nasal bacterial colonization (OR = 0.99, 95% CI: 0.868-1.38, P: 0.7) and bacterium in urine (OR = 0.502, 95% CI: 0.07-3.598, P: 0.703) did not pose a significant risk for periprosthetic infection.

CONCLUSION

According to our findings, the CRP / albumin ratio has a more prognostic capacity than other risks in determining the risk of periprosthetic infection for total joint arthroplasty. CRP / albumin ratio is a cheap and easy to apply marker. Routine urine and nasal bacteria screening is not required before total joint arthroplasty.

Culture-Independent Genotyping, Virulence and Antimicrobial Resistance Gene Identification of Staphylococcus aureus from Orthopaedic Implant-Associated Infections

Our culture-independent nanopore shotgun metagenomic sequencing protocol on biopsies has the potential for same-day diagnostics of orthopaedic implant-associated infections (OIAI). As OIAI are frequently caused by Staphylococcus aureus, we included S. aureus genotyping and virulence gene detection to exploit the protocol to its fullest. The aim was to evaluate S. aureus genotyping, virulence and antimicrobial resistance genes detection using the shotgun metagenomic sequencing protocol. This proof of concept study included six patients with S. aureus-associated OIAI at Akershus University Hospital, Norway. Five tissue biopsies from each patient were divided in two: (1) conventional microbiological diagnostics and genotyping, and whole genome sequencing (WGS) of S. aureus isolates; (2) shotgun metagenomic sequencing of DNA from the biopsies. Consensus sequences were analysed using spaTyper, MLST, VirulenceFinder, and ResFinder from the Center for Genomic Epidemiology (CGE). MLST was also compared using krocus. All spa-types, one CGE and four krocus MLST results matched Sanger sequencing results. Virulence gene detection matched between WGS and shotgun metagenomic sequencing. ResFinder results corresponded to resistance phenotype. S. aureus spa-typing, and identification of virulence and antimicrobial resistance genes are possible using our shotgun metagenomics protocol. MLST requires further optimization. The protocol has potential application to other species and infection types.

Is Preoperative Staphylococcus aureus Screening and Decolonization Effective at Reducing Surgical Site Infection in Patients Undergoing Orthopedic Surgery? A Systematic Review and Meta-Analysis With a Special Focus on Elective Total Joint Arthroplasty

BACKGROUND

Staphylococcus aureus is a major pathogen implicated in orthopedic infections worldwide. Preoperative decolonization has been promoted but different strategies present mixed results. Thus, the goals of this study are to determine (1) whether S aureus screening and/or decolonization is effective at reducing surgical site infection in orthopedic surgery, (2) with a special focus on elective total joint arthroplasty (TJA), and (3) which preoperative S aureus screening/treatment strategy is most cost-effective for TJA.

METHODS

PubMed, Ovid MEDLINE, and Cochrane databases were searched on January 1, 2020, using a systematic strategy. We included papers with data comparing surgical site infection and periprosthetic joint infection rate in orthopedic surgery and/or elective total hip and knee arthroplasty patients before/after S aureus screening and/or decolonization protocol and papers evaluating the cost-effectiveness of different S aureus screening/treatment strategies.

RESULTS

A total of 1260 papers were screened, and 32 papers were ultimately included. Results showed an increased risk of developing any infection (relative risk [RR] = 1.71 ± 0.16) and S aureus infection (RR = 2.79 ± 0.45) after orthopedic surgery without previous nares and whole-body decolonization. Focusing exclusively on elective TJA, there was an increased risk of developing any infection (RR = 1.70 ± 0.17) and S aureus infection (RR = 2.18 ± 0.41) if no decolonization is performed. All strategies appeared to be cost-effective, although universal decolonization without screening seemed to be the most advantageous.

CONCLUSION

Preoperative S aureus screening/decolonization protocol lowered the risk of infection after elective orthopedic and TJA surgeries. However, further studies are needed to determine optimal clinical and cost-effective methodologies.

Molecular characteristics of Staphylococcus aureus associated prosthetic joint infections after hip fractures treated with hemiarthroplasty: a retrospective genome-wide association study

A retrospective study of Staphylococcus aureus isolates from orthopaedic patients treated between 2000 and 2017 at Akershus University Hospital, Norway was performed using a genome-wide association approach. The aim was to characterize and investigate molecular characteristics unique to S. aureus isolates from HHA associated prosthetic joint infections and potentially explain the HHA patients' elevated 1-year mortality compared to a non-HHA group. The comparison group consisted of patients with non-HHA lower-extremity implant-related S. aureus infections. S. aureus isolates from diagnostic patient samples were whole-genome sequenced. Univariate and multivariate analyses were performed to detect group-associated genetic signatures. A total of 62 HHA patients and 73 non-HHA patients were included. Median age (81 years vs. 74 years; p < 0.001) and 1-year mortality (44% vs. 15%, p < 0.001) were higher in the HHA group. A total of 20 clonal clusters (CCs) were identified; 75% of the isolates consisted of CC45, CC30, CC5, CC15, and CC1. Analyses of core and accessory genome content, including virulence, resistance genes, and k-mer analysis revealed few group-associated variants, none of which could explain the elevated 1-year mortality in HHA patients. Our findings support the premise that all S. aureus can cause invasive infections given the opportunity.

Exploratory clinical trial on the safety and bactericidal effect of 222-nm ultraviolet C irradiation in healthy humans

Introduction

Surgical site infection is one of the most severe complications of surgical treatments. However, the optimal procedure to prevent such infections remains uninvestigated. Ultraviolet radiation C (UVC) with a short wavelength has a high bactericidal effect; however, it is cytotoxic. Nonetheless, given that UVC with a wavelength of 222 nm reaches only the stratum corneum, it does not affect the skin cells. This study aimed to investigate the safety of 222-nm UVC irradiation and to examine its skin sterilization effect in healthy volunteers.

Methods

This trial was conducted on 20 healthy volunteers. The back of the subject was irradiated with 222-nm UVC at 50–500 mJ/cm², and the induced erythema (redness of skin) was evaluated. Subsequently, the back was irradiated with a maximum amount of UVC not causing erythema, and the skin swabs before and after the irradiation were cultured. The number of colonies formed after 24 hours was measured. In addition, cyclobutene pyrimidine dimer (CPD) as an indicator of DNA damage was measured using skin tissues of the nonirradiated and irradiated regions.

Results

All subjects experienced no erythema at all doses. The back of the subject was irradiated at 500 mJ/cm², and the number of bacterial colonies in the skin swab culture was significantly decreased by 222-nm UVC irradiation. The CPD amount produced in the irradiated region was slightly but significantly higher than that of the non-irradiated region.

Conclusion

A 222-nm UVC at 500 mJ/cm² was a safe irradiation dose and possessed bactericidal effects. In the future, 222-nm UVC irradiation is expected to contribute to the prevention of perioperative infection.

Nasal colonization with Staphylococcus aureus is a risk factor for ventricular assist device infection in the first year after implantation: A prospective, single-centre, cohort study

OBJECTIVES

To assess, whether S. aureus nasal colonization is a risk factor for infections in patients with durable ventricular assist device (VAD).

METHODS

Prospective, single-centre, cohort study (i) ascertaining S. aureus nasal colonization status of patients admitted for VAD-implantation and detecting time to first episode of VAD-specific or -related infection according to International Society for Heart and Lung Transplantation criteria during follow-up and (ii) comparing whole genomes of S. aureus from baseline colonization and later infection.

RESULTS

Among 49 patients (17 colonized, 32 non-colonized), S. aureus VAD-infections occurred with long latency after implantation (inter quartile range 76-217 days), but occurred earlier (log-rank test P = 0.006) and were more common (9/17, 52.9% vs. 4/32, 12.5%, P = 0.005; incidence rates 2.81 vs. 0.61/1000 patient days; incidence rate ratio 4.65, 95% confidence interval 1.30-20.65, P = 0.009) among those nasally colonized with S. aureus before implantation. We found a similar but less pronounced effect of colonization status when analysing its effect on all types of VAD-infections (10/17, 58.8% vs. 7/32, 21.9%, P = 0.01). These findings remained robust when adjusting for potential confounders and restricting the analysis to 'proven infections'. 75% (6/8) of paired S. aureus samples from colonization and VAD-infection showed concordant whole genomes.

CONCLUSIONS

In patients with durable VAD, S. aureus nasal colonization is a source of endogenous infection, often occurring months after device-implantation and affecting mostly the driveline. Hygiene measures interrupting the endogenous route of transmission in VAD-patients colonized with S. aureus long-term may about half the burden of infections and require clinical scrutiny.

Staphylococcus aureus: A predominant cause of surgical site infections in a rural healthcare setup of Uttarakhand

Introduction:

Surgical site infections (SSIs) represent the second most common type of healthcare-associated infections and remain a relatively common postoperative complication and the most common reason for readmission after surgery. SSIs have dire implications for the surgeon, patient, and institution which often require prolonged treatment, impose an economic burden and double the risk of patient mortality. Staphylococcus aureus is currently the most common cause of SSIs causing as many as 37% of cases of SSIs in community hospitals with methicillin-resistant S. aureus (MRSA) of particular concern.

Materials and Methods:

This cross-sectional study was conducted from January 2014 to December 2014 in a rural tertiary care hospital of Pauri Garhwal district of Uttarakhand state, India. Samples were collected using sterile cotton swabs from 269 patients clinically diagnosed with SSIs and were processed as per standard microbiological techniques. Antimicrobial susceptibility testing was done using a modified Kirby-Bauer disc diffusion method.

Results:

Out of 1294 patients, 269 (20.8%) were found to have SSIs and samples were collected from them. Out of a total of 269 samples, 258 (95.9%) yielded bacterial growth and 267 bacterial isolates were obtained. S. aureus (45.3%) was the commonest organism followed by Escherichia coli (13.9%), Pseudomonas aeruginosa (6.7%), and Proteus species (4.9%). Antimicrobial profile of S. aureus revealed maximum sensitivity to rifampicin, linezolid, teicoplanin, vancomycin, and amikacin whereas ampicillin, cefazolin, and gentamicin were found to be least sensitive.

Conclusion:

S. aureus played a predominant role in the etiology of SSIs in this hospital with MRSA being a major concern as the treatment options for such resistant strains are limited. Reduction in SSI rates can lead to both better clinical outcomes for patients and cost savings for hospitals. Adherence to strict infection control measures, maintenance of proper hand hygiene and optimal preoperative, intraoperative, and postoperative patient care can surely reduce the incidence of SSIs. A multifaceted approach involving the surgical team, microbiologist, and the infection control team is required to provide quality surgical services.

Evidence-based Care Bundles for Preventing Surgical Site Infections in Spinal Instrumentation Surgery

STUDY DESIGN

A retrospective study, using prospectively collected data.

OBJECTIVE

The aim of this study was to evaluate the impact of evidence-based care bundles for preventing surgical site infections (SSIs) in spinal instrumentation surgery.

SUMMARY OF BACKGROUND DATA

About half of all SSIs are preventable via evidence-based methods. For successful SSI prevention, the bacterial load must be minimized, and methicillin-resistant Staphylococcus aureus (MRSA) protection must be maximized. However, it is difficult to cover all of these requirements by single preventative method.

METHODS

We screened consecutive patients scheduled for spinal instrumentation surgeries at a single tertiary referral hospital for high surgical, SSI, and MRSA colonization risks. Evidence-based care bundles were implemented for high-risk patients and included 1) additional vancomycin prophylaxis, 2) diluted povidone-iodine irrigation, and 3) nasal and body decontamination. Patient demographics, comorbidities, operative features, and SSIs reported to the Japanese Nosocomial Infections Surveillance system were prospectively obtained in the same method by the same assessor and were used for the analyses. The results were compared before and after the application of the bundle.

RESULTS

There were 1042 spinal instrumentation surgeries (741 before and 301 after care bundles) performed from November 2010 to December 2015. Of 301 surgeries, 57 cases (18.9%) received care bundles. There were no significant differences in patient backgrounds before and after the intervention. The SSI rate decreased significantly from 3.8% to 0.7% (P < 0.01) after the intervention, with an overall 82% relative risk reduction. A significant protective effect was observed in the multivariate analysis (adjusted odds ratio 0.18, 95% confidence interval: 0.04-0.77, P = 0.02). There were no MRSA-related SSIs among those that received care bundles, even though MRSA was the predominant pathogen in the study population.

CONCLUSION

Evidence-based care bundles, applied in selected high-risk spinal instrumentation cases, minimized bacterial load, maximized MRSA protection, and significantly reduced SSI rates without topical vancomycin powder.

LEVEL OF EVIDENCE

4.

The development of a staphylococcus aureus four antigen vaccine for use prior to elective orthopedic surgery

Staphylococcus aureus (S. aureus) is a challenging bacterial pathogen which can cause a range of diseases, from mild skin infections, to more serious and invasive disease including deep or organ space surgical site infections, life-threatening bacteremia, and sepsis. S. aureus rapidly develops resistance to antibiotic treatments. Despite current infection control measures, the burden of disease remains high. The most advanced vaccine in clinical development is a 4 antigen S. aureus vaccine (SA4Ag) candidate that is being evaluated in a phase 2b/3 efficacy study in patients undergoing elective spinal fusion surgery (STaphylococcus aureus suRgical Inpatient Vaccine Efficacy [STRIVE]). SA4Ag has been shown in early phase clinical trials to be generally safe and well tolerated, and to induce high levels of bactericidal antibodies in healthy adults. In this review we discuss the design of SA4Ag, as well as the proposed clinical development plan supporting licensure of SA4Ag for the prevention of invasive disease caused by S. aureus in elective orthopedic surgical populations. We also explore the rationale for the generalizability of the results of the STRIVE efficacy study (patients undergoing elective open posterior multilevel instrumented spinal fusion surgery) to a broad elective orthopedic surgery population due to the common pathophysiology of invasive S. aureus disease and commonalties of patient and procedural risk factors for developing postoperative S. aureus surgical site infections.

Risk Factors for Staphylococcus aureus Nasal Colonization in Joint Arthroplasty Patients

BACKGROUND

Several studies have shown that Staphylococcus aureus (S aureus) nasal colonization is associated with surgical site infection and that preoperative decolonization can reduce infection rates. Up to 30% of joint arthroplasty patients have positive S aureus nasal swabs. Patient risk factors for colonization remain largely unknown. The aim of this study was to determine whether there is a specific patient population at increased risk of S aureus nasal colonization.

METHODS

This study is a retrospective review of 716 patients undergoing hip or knee arthroplasty beginning in 2011. All patients were screened preoperatively for nasal colonization. Univariate and multivariate analyses were used to assess risk factors for nasal colonization.

RESULTS

A total of 716 patients undergoing joint arthroplasty had preoperative nasal screening. One hundred twenty-five (17.50%) nasal swabs were positive for methicillin-susceptible S aureus (MSSA), 13 (1.80%) were positive for methicillin-resistant S aureus (MRSA), and 84 (11.70%) were positive for other organisms. In bivariate analysis, diabetes (P = .04), renal insufficiency (P = .03), and immunosuppression (P = .02) were predictors of nasal colonization with MSSA/MRSA. In multivariate analysis, immunosuppression (P = .04; odds ratio, 2.0; 95% confidence interval, 1.03-3.71) and renal insufficiency (P = .04; odds ratio, 2.5; 95% confidence interval, 1.01-6.18) were independent predictors of nasal colonization with MSSA/MRSA.

CONCLUSION

Overall, 17.5% of patients undergoing primary hip or knee arthroplasty screened positive for S aureus. Diabetes, renal insufficiency, and immunosuppression are risk factors for such colonization. Given that these comorbidities are already known independent risk factors for periprosthetic joint infection, these patients should be particularly screened and when necessary, decolonized.

Patient and surgical factors affecting procedure duration and revision risk due to deep infection in primary total knee arthroplasty

BACKGROUND

The aim of this study was to assess which patient and procedure factors affected both the risk of infection as well as procedure duration. Additionally, to assess if procedure duration affected the revision risk due to deep infection in total knee arthroplasty (TKA) patients and in a subgroup of low-risk patients.

METHODS

28,262 primary TKA with 311 revisions due to deep infection were included from the Norwegian Arthroplasty Register (NAR) and analysed from primary surgery from 2005 until 31st December 2015 with a 1 and 4 year follow up. The risk of revision due to deep infection was calculated in a multivariable Cox regression model including patient and procedure related risk factors, assessing Hazard Ratio (HR) with 95% confidence interval (CI).

RESULTS

Multivariate analysis showed statistically significant associations with revision due to deep infection and increased procedure duration for male patients, ASA3+ (American Society of Anesthesiologists) and perioperative complications. Procedure duration ≥110 min (75 percentile) had a higher risk of deep infection compared to duration <75 min (25 percentile), in the unadjusted analysis (HR = 1.8, 95% CI 1.3-2.5, p = 0.001) and in the adjusted analysis (HR = 1.5, 95% CI 1.0-2.1, p = 0.03). For low-risk patients, procedure duration did not increase the risk of infection.

CONCLUSION

Male patients, ASA 3+ patients and perioperative complications were risk factors both for longer procedure duration and for deep infection revisions. Patients with a high degree of comorbidity, defined as ASA3+, are at risk of infection with longer procedure durations. The occurrence of perioperative complications potentially leading to a more complex and lengthy procedure was associated with a higher risk of infection. Long procedure duration in itself seems to have minor impact on infection since we found no association in the low-risk patient.

Vaccine development to prevent Staphylococcus aureus surgical-site infections

BACKGROUND

Staphylococcus aureus surgical-site infections (SSIs) are a major cause of poor health outcomes, including mortality, across surgical specialties. Despite current advances as a result of preventive interventions, the disease burden of S. aureus SSI remains high, and increasing antibiotic resistance continues to be a concern. Prophylactic S. aureus vaccines may represent an opportunity to prevent SSI.

METHODS

A review of SSI pathophysiology was undertaken in the context of evaluating new approaches to developing a prophylactic vaccine to prevent S. aureus SSI.

RESULTS

A prophylactic vaccine ideally would provide protective immunity at the time of the surgical incision to prevent initiation and progression of infection. Although the pathogenicity of S. aureus is attributed to many virulence factors, previous attempts to develop S. aureus vaccines targeted only a single virulence mechanism. The field has now moved towards multiple-antigen vaccine strategies, and promising results have been observed in early-phase clinical studies that supported the recent initiation of an efficacy trial to prevent SSI.

CONCLUSION

There is an unmet medical need for novel S. aureus SSI prevention measures. Advances in understanding of S. aureus SSI pathophysiology could lead to the development of effective and safe prophylactic multiple-antigen vaccines to prevent S. aureus SSI.

Prior Staphylococcus Aureus Nasal Colonization: A Risk Factor for Surgical Site Infections Following Decolonization

INTRODUCTION

Staphylococcus aureus (S aureus) decolonization regimens are being used to mitigate the risk of surgical site infection (SSI). However, their efficacy is controversial, with mixed results reported in the literature.

METHODS

Before undergoing primary total knee arthroplasty (TKA), total hip arthroplasty (THA), or spinal fusion, 13,828 consecutive patients were screened for nasal S aureus and underwent a preoperative decolonization regimen. Infection rates of colonized and noncolonized patients were compared using unadjusted logistic regression. An adjusted regression analysis was performed to determine independent risk factors for SSI.

RESULTS

The rate of SSI in colonized patients was 4.35% compared with only 2.39% in noncolonized patients. In our TKA cohort, unadjusted logistic regression identified S aureus colonization to be a significant risk factor for SSI (odds ratio [OR], 2.9; P < 0.001). After controlling for other potential confounders including age, body mass index, tobacco use, and American Society of Anesthesiologists score, an SSI was 3.8 times more likely to develop in patients colonized with S aureus (OR, 3.8; P = 0.0025). The THA and spine colonized patients trended toward higher risk in both unadjusted and adjusted models; however, the results were not statistically significant.

DISCUSSION

The results of our study suggest that decolonization may not be fully protective against SSI. The risk of infection after decolonization is not lowered to the baseline of a noncolonized patient.

LEVEL OF EVIDENCE

Level IV.

Prevalence and Risk Factors of Colonization with Staphylococcus aureus in Healthy Pet Cats Kept in the City Households

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is a significant pathogen in both human medicine and veterinary medicine. The importance of pets as reservoirs of human infections is still poorly understood. This article provides detailed information of a cross-sectional study of a S. aureus colonization in clinically healthy indoor cats. The study systematically assessed a number of different anatomical locations for the S. aureus colonization and the influence of a range of potential risk factors on the value of the final S. aureus colonization rate. The incidence rates observed for cats with at least one site positive for S. aureus or MRSA were 17.5% and 6.63%, respectively. The following risk factors were identified: one or more owners working in the healthcare industry (human or veterinary); dogs being kept with the cat under investigation; treatment of the cat under investigation with antibiotics or chemotherapeutics during the previous year. In conclusion, this study revealed a higher prevalence of MRSA than what has previously been reported in healthy pets. A combination of anatomical locations from which the samples were collected had a major influence on the final value of the S. aureus colonization rate.

The Prevalence of MRSA Nasal Carriage in Preoperative Pediatric Orthopaedic Patients

Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) has been described as a risk factor for postsurgical infection. The purpose of this study is to determine the prevalence of MRSA in pediatric orthopaedic patients and whether being a MRSA carrier is a predictor of postoperative infection. Six hundred and ninety-nine consecutive pediatric patients who underwent MRSA nasal screening prior to surgery were studied. Postoperative cultures, total surgical site infections (SSIs), and epidemiological and surgical prophylaxis data were reviewed. Forty-four of 699 patients (6.29%) screened positive for MRSA. Nine of the 44 patients (20.5%) that screened positive for MRSA had a subsequent SSI compared to 10 of the 655 patients (1.52%) that screened negative (p < 0.05). All 9 patients with a SSI had myelomeningocele. The prevalence of MRSA was 6.30% and was predictive of postoperative infection. Children with myelomeningocele were at the highest risk for having a positive MRSA screening and developing SSI.

Is the Colonisation of Staphylococcus aureus in Pets Associated with Their Close Contact with Owners?

In human beings and animals, staphylococci constitute part of the normal microbial population. Staphylococcus aureus could be classified as an opportunistic pathogen because the bacteria are noted in clinically healthy individuals, but when the immune system becomes compromised, they can also cause a wide range of infections. The objective of this study was to test the hypothesis that cats who are in close contact with their owners are at the greatest risk of being colonised with S. aureus. Two groups of cats were investigated: single, pet (domestic) cats that do not have outdoor access; and a local population of feral cats living in urban areas. The prevalence of S. aureus in domestic cats was 19.17%, while it's prevalence in the feral cat population was only 8.3%; which was statistically significant. Analysis of antibiotic resistance, at the genotypic as well as phenotypic level, showed that S. aureus isolates from pet cats were more likely to harbour antibiotic resistant determinants. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in households was 10.21%, while in feral cats it was only 1.4%. In conclusion, this study has revealed a correlation between close contact with humans and a higher risk of the cats being colonised with S. aureus and harbouring the antibiotic resistant determinants.

Risk Factors for Infection Following Total Knee Arthroplasty: A Series of 3836 Cases from One Institution

Higher PJI rates may be related to identifiable risk factors, which may or may not be modifiable. Identifying risk factors preoperatively provides opportunities for modification and potentially decreasing the incidence of PJI. The purposes of this study were to: (1) retrospectively identify and quantify risk factors for PJI following primary TKA, and (2) to classify those significant risk factors as either non-modifiable or modifiable for intervention prior to surgery. Optimization of modifiable risk factors such as Staphylococcus aureus colonization, and tobacco use prior to primary TKA may decrease the incidence of periprosthetic joint infection after primary TKA, thereby reducing morbidity and the costs associated with treating those infections.

The Current State of Screening and Decolonization for the Prevention of Staphylococcus aureus Surgical Site Infection After Total Hip and Knee Arthroplasty

The most common pathogens in surgical site infections after total hip and knee arthroplasty are methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and coagulase-negative staphylococci. Patients colonized with MSSA or MRSA have an increased risk for a staphylococcal infection at the site of a total hip or knee arthroplasty. Most colonized individuals who develop a staphylococcal infection at the site of a total hip or total knee arthroplasty have molecularly identical S. aureus isolates in their nares and wounds. Screening and nasal decolonization of S. aureus can potentially reduce the rates of staphylococcal surgical site infection after total hip and total knee arthroplasty.

Twenty Percent of Patients May Remain Colonized With Methicillin-resistant Staphylococcus aureus Despite a Decolonization Protocol in Patients Undergoing Elective Total Joint Arthroplasty

BACKGROUND

Staphylococcus aureus is the most commonly isolated organism in periprosthetic joint infection (PJI). Resistant strains such as methicillin-resistant S aureus (MRSA) are on the rise, and many programs have instituted decolonization protocols. There are limited data on the success of S aureus nasal decolonization programs and their impact on PJI.

QUESTIONS/PURPOSES

The purposes of this study were to (1) determine the proportion of patients successfully decolonized using a 2-week protocol; (2) compare infection risks between our surveillance and decolonization protocol group against a historical control cohort to evaluate changes in proportions of S aureus infections; and (3) assess infection risk based on carrier type, comparing S aureus carriers with noncarrier controls.

METHODS

We retrospectively evaluated a group of 3434 patients who underwent elective primary and revision hip and knee arthroplasty over a 2-year period; each patient in the treatment group underwent a surveillance protocol, and a therapeutic regimen of mupurocin and chlorhexidine was instituted when colonization criteria were met. A 2009 to 2010 comparative historical cohort was chosen as the control group. We compared risks of infection between our treatment group and the historical control cohort. Furthermore, in patients who developed surgical site infections (SSIs), we compared the proportions of each S aureus type between the two cohorts. Finally, we compared infection rates based on carrier status. Surveillance for infection was carried out by the hospital infection control coordinator using the Centers for Disease Control and Prevention (CDC) criteria. During the time period of this study, the CDC defined hospital-acquired infection related to a surgical procedure as any infection diagnosed within 1 year of the procedure. With the numbers available, we had 41% power to detect a difference of 0.3% in infection rate between the treatment and control groups. To achieve 80% power, a total of 72,033 patients would be needed.

RESULTS

Despite the protocol, 22% (26 of 121) of patients remained colonized with MRSA. With the numbers available, there were no differences in infection risk between the protocoled group (27 of 3434 [0.8%]) and the historical control group (33 of 3080 [1.1%]; relative risk [RR], 0.74; 95% confidence interval [CI], 0.44-1.22; p = 0.28). In terms of infecting organism in those who developed SSI, S aureus risk decreased slightly (treatment: 13 of 3434 patients [0.38%]; control: 21 of 3080 patients [0.68%]; RR, 0.56; CI, 0.28-1.11; p = 0.11). Within the protocoled group, carriers had a slightly higher risk of developing SSI (carrier: seven of 644 [1.1%]; noncarrier: 18 of 2763 [0.65%]; RR, 1.77; CI, 0.74-4.24; p = 0.20).

CONCLUSIONS

The screening and decolonization protocol enabled a substantial reduction in nasal carriage of MRSA, but some patients remained colonized. However, our nasal decolonization protocol before elective total joint arthroplasty did not demonstrate a decrease in the proportion of patients developing SSI. Future meta-analyses and systematic reviews will be needed to pool the results of studies like these to ascertain whether small improvements in infection risk are achieved by protocols like ours and to determine whether any such improvements warrant the costs and potential risks of surveillance and intervention.

LEVEL OF EVIDENCE

Level III, therapeutic study.

No change in the distribution of types and antibiotic resistance in clinical Staphylococcus aureus isolates from orthopaedic patients during a period of 12 years

Staphylococcus aureus (S. aureus) is the most common cause of bone and joint infections. However, limited information is available on the distribution of S. aureus geno- and phenotypes causing orthopaedic infections. The aim of this study was to identify the dominating types causing infections in orthopaedic patients, investigate if the characteristics of these types changed over time and examine if different types were more often associated with surgical site infection (SSI) than primary infection (non-SSI). All clinical S. aureus isolates collected from orthopaedic patients from 2000 through 2011 at Akershus University Hospital, Norway, were characterised by S. aureus protein A (spa) typing and tested for antibiotic resistance. A total of 548 patients with orthopaedic S. aureus infections were included, of which 326 (59 %) had SSI and 222 (41 %) had non-SSI. The median age was 62 years [range 2-97 years] and 54 % were male. Among the 242 unique spa types, t084 was the most common (7 %). Penicillin resistance was identified in 75 % of the isolates, whereas the resistances to the other antibiotics tested were <5 %. Three isolates (0.5 %) were resistant to methicillin. There was no significant difference in the distribution of geno- and phenotypes over time and there was no difference in types between SSI and non-SSI. In this large collection of S. aureus from orthopaedic patients, the S. aureus infections, regardless of origin, were heterogeneous, mainly resistant to penicillin, stable over time and consisted of similar types as previously found in both carrier and other patient populations.

Preoperative Prevalence of Staphylococcus aureus in Cardiothoracic and Neurological Surgical Patients

Methicillin-resistant Staphylococcus aureus (MRSA) is a global cause of both hospital and community-acquired infection. This retrospective, observational study determined the prevalence of MRSA carriers in cardiothoracic and neurological surgical patients presenting to an outpatient preoperative assessment center in Columbus, OH. Aggressive skin and soft-tissue infection may be caused by MRSA with potentially fatal complications. Cardiothoracic and neurological surgical patients are at high risk for surgical-site infection. Results indicated that 4.25% of the sample carried MRSA and 25.25% carried methicillin-sensitive S. aureus.