Device and surgical procedure-related infections in Canadian acute care hospitals from 2011 to 2020

Background Healthcare-associated infections (HAIs) continue to place a burden on patient health and safety as well as on the healthcare system. In Canada, national surveillance of HAIs at sentinel acute care hospitals is conducted by the Canadian Nosocomial Infection Surveillance Program. This article describes ten years of device and surgical procedure-related HAI epidemiology in Canada from 2011 to 2020. Methods Data were collected from over 40 Canadian sentinel acute care hospitals between January 1, 2011, and December 31, 2020, for central line-associated bloodstream infections (CLABSIs), hip and knee surgical site infections (SSIs), cerebrospinal fluid shunt SSIs and paediatric cardiac SSIs. Case counts, rates, patient and hospital characteristics, pathogen distributions, and antimicrobial resistance are presented. Results Between 2011 and 2020, 4,751 device and surgical procedure-related infections were reported, with CLABSIs in intensive care units (ICUs) representing 67% (n=3,185) of all reported infections. Over the surveillance period, significant rate increases were observed in adult mixed ICU CLABSIs (0.8 to 1.6 per 1,000 line days, p=0.004) while decreases were observed in neonatal ICU CLABSIs (4.0 to 1.6 per 1,000 line days, p=0.002) and SSIs following knee arthroplasty (0.69 to 0.29 infections per 100 surgeries, p=0.002). No trends were observed in the other reported HAIs. Of the 5,071 pathogens identified, the majority were gram-positive (68%), followed by gram-negative (23%) and fungi (9%). Coagulase-negative staphylococci (27%) and Staphylococcus aureus (16%) were the most frequently isolated pathogens. Conclusion This report describes epidemiological and microbiological trends among select device and surgical procedure-related HAIs, essential for benchmarking infection rates nationally and internationally, to identify any changes in infection rates or antimicrobial resistance patterns and to help inform hospital infection prevention and control and antimicrobial stewardship policies and programs.


Introduction
Healthcare-associated infections (HAIs) threaten patient safety and quality of care, contributing to prolonged hospital stays, increased antimicrobial resistance, costs to the health system and unnecessary deaths (1). Healthcare-associated infections may arise through the use of invasive devices, surgical procedures and inappropriate antibiotic use (2). A 2017 point prevalence study at Canadian sentinel acute care hospitals found that device and surgical procedure-related infections accounted for 35.6% of all reported HAIs (3). Among these device and surgical procedure-related infections, 19.4% of surgical site infections (SSIs) were associated with a prosthetic implant while 21.2% were associated with central line-associated bloodstream infections (CLABSIs) (3). The risk of device and surgical procedure-related HAIs varies among patient populations and within hospital types, with patients admitted to the intensive care unit (ICU) being at higher risk of developing a HAI (4). During the coronavirus disease 2019 (COVID-19) pandemic declared by the World Health Organization on March 11, 2020 (5), rates of HAIs and antimicrobial resistance (AMR) may have been impacted by necessary changes to hospital infection prevention and control practices and antimicrobial stewardship (6).
Antimicrobial resistance is known to impact length of stay and healthcare costs (7). It is expected that by 2050 an estimated 10 million annual deaths will be attributable to AMR (8); thus, antimicrobial susceptibility information is key to ensuring appropriate treatment and use of antimicrobials to help reduce AMR (9).
Understanding the trends in device and surgical procedurerelated HAIs is essential to provide benchmark rates over time which helps to inform effective antimicrobial stewardship and infection prevention and control measures. This report provides an epidemiological overview of select device and surgical procedure-related HAIs from 2011 to 2020 in over 40 Canadian Nosocomial Infection Surveillance Program (CNISP) hospitals.

Methods Design
Since its establishment in 1994, CNISP has conducted national HAI surveillance at sentinel acute care hospitals across Canada, in collaboration with the Public Health Agency of Canada and the Association of Medical Microbiology and Infectious Disease Canada. Data are presented for the following device and surgical procedure-related HAIs: central line-associated bloodstream infections (CLABSIs); hip and knee arthroplasty SSIs; cerebrospinal fluid (CSF) shunt SSIs; and paediatric cardiac SSIs.

Case definitions
Device and surgical procedure-related HAIs were defined according to standardized protocols and expert-reviewed case definitions (see Appendix). Only complex infections, defined as deep incisional and organ/space, were included in hip and knee SSI surveillance, while only CLABSIs identified in ICU settings. Adult mixed ICU, adult cardiovascular surgery intensive care unit (CVICU), paediatric intensive care unit (PICU) and neonatal intensive care unit (NICU) were included in CLABSI surveillance.

Data source
Epidemiological data on device and surgical procedure-related infections occurring between January 1, 2011 and December 31, 2020 were submitted by participating hospitals. Data submission and case identification were supported by training sessions and periodic evaluations of data quality.

Statistical analysis
To calculate hip and knee SSI, CSF shunt SSI and paediatric cardiac SSI rates, the number of cases were divided by the number of surgical procedures performed (multiplied by 100). To calculate CLABSI rates, the number of cases were divided by line day denominators (multiplied by 1,000). To calculate proportions of pathogens, the number of pathogens were divided by the total number of identified pathogens. Denominators may vary, as missing and incomplete data were excluded from analyses. Interquartile ranges (IQR) were calculated. Trends over time were tested using the Mann-Kendall test. Significance testing was twotailed and differences were considered significant at a p-value of ≤0.05. Analyses were conducted using R version 4.1.2 and SAS 9.4.    Figure 2 and Table A2).      (Table A4). While rates remained generally consistent over the surveillance period (p=0.089), there was a significant increase in 2018 (7.5 infections per 100 surgeries, p<0.001) compared to the overall rate from 2011 to 2017 (3.5 infections per 100 surgeries) (Figure 4), which was an outlier attributable to two hospitals where investigations are ongoing. Since 2018, the rate decreased by 48% from 7.5 to 3.9 infections per 100 surgeries in 2020, returning to rates observed prior to 2018.

Antibiogram
Results of antimicrobial susceptibility testing for the most frequently identified gram-positive, gram-negative and fungal pathogens from device and surgical procedure-related HAIs are listed in Table 5 and

Discussion
This report summarizes 4,751 device and surgical procedurerelated HAIs identified over 10 years of surveillance from 2011 to 2020. Rates of device and surgical procedure-related HAIs have doubled for adult mixed ICU CLABSIs while NICU CLABSI and knee SSI rates have significantly decreased 60% and 58%, respectively. The most frequently reported pathogens in this report were generally aligned with those reported in a 2020 United States (US) National Healthcare Surveillance Network (NHSN) report of adult HAIs, indicating S. aureus, E. coli and Klebsiella among the most frequently reported pathogens for device and surgical procedure-related HAIs in both Canada and the US, while CoNS was identified more commonly in Canada (9). The COVID-19 pandemic may have had differing impacts on the rates of device and surgical procedure-related HAIs in Canada and the US (10). Investigation is underway to assess the influence of pandemic-related factors such as changes in infection control practices, hospital resource capacity, screening, laboratory testing and antimicrobial stewardship on the observed rates of HAIs.

Central line-associated bloodstream infections
The overall rates of CLABSI in adult ICUs (0.6 and 1.1 per 1,000 line days for CVICUs and mixed ICUs, respectively) were similar

Surgical site infections
Among SSIs included in this surveillance report, hip and knee SSIs were the most common. Hip SSI rates remained stable across the reported years, while a decreasing trend in knee SSI rates was observed. Surveillance from the European Centre for Disease Prevention and Control reported similar trends, indicating stable hip SSI rates and decreasing knee SSI rates for study years 2014 to 2017 (20). In a US point prevalence study, a reduction in the prevalence of complex SSIs was observed between 2011 and 2015 (21). In accordance with pathogen results from other regions, the most common pathogens among hip and knee-SSIs were S. aureus and CoNS (20,22). Frequent identification of these two pathogens may be attributable to the use of implant devices and contamination from the patient's endogenous skin flora (9). Joint replacements typically occur in older adults, which explains the high median age for hip and knee SSI (23). Joint replacements among older populations are SURVEILLANCE   also prone to surgical complications, such as prosthetic joint infections (23). Data indicate that surgical site infections frequently lead to readmission and revision surgery, both of which result in high financial and resource burdens on the healthcare system (24).
The overall rate of surgical site infections from CSF shunts was 2.9 per 100 surgeries. This aligns with rates reported from a 2012 multi-country review, which range from 3% to 12% (25

Antibiogram
The percentage of S. aureus isolates that were MRSA in this study (14%-15%) ( Table 5 and Table 6

Strengths and limitations
The main strength of this study is the standardized collection of detailed data from a large network of sentinel hospitals for over ten years. The CNISP network extends across Canada, although it may not be representative of all Canadian acute care hospitals since the number of hospitals participating in each HAI surveillance project differed. However, recruitment is ongoing and CNISP coverage of Canadian acute care beds increased from 25% in 2011 to 30% in 2020. The CNISP is continuing to increase representativeness, especially among northern, community, rural and Indigenous populations.
The epidemiologic data collected were limited to the information available in the patient charts. For CLABSI surveillance, data were limited to infections occurring in the ICU settings, and as such may only represent a portion of CLABSIs occurring in the hospital. Further, differences in surveillance protocols and case definitions, as well as the lack of recent comparable data, limit comparison with data from other countries. The CNISP continues to support the national public health response to the COVID-19 pandemic. Future studies are ongoing to assess the impact of the COVID-19 pandemic on device and surgical procedure-related HAIs and AMR.

Conclusion
This report provides an updated summary of rates, pathogen distributions and antimicrobial resistance among select device and surgical procedure-related HAIs and relevant pathogens. The collection and analysis of national surveillance data are key to understanding and reducing the national burden of device and surgical procedure-related HAIs by providing benchmark rates for comparison nationally and internationally and informing antimicrobial stewardship and infection prevention and control programs and policies.