Camille Lemieux

Outbreak of Multidrug-Resistant Pseudomonas aeruginosa Colonization and Infection Secondary to Imperfect Intensive Care Unit Room Design

BACKGROUND Pseudomonas aeruginosa has been increasingly recognized for its ability to cause significant hospital-associated outbreaks, particularly since the emergence of multidrug-resistant strains. Biofilm formation allows the pathogen to persist in environmental reservoirs. Thus, multiple hospital room design elements, including sink placement and design, can impact nosocomial transmission of P. aeruginosa and other pathogens. METHODS From December 2004 through March 2006, 36 patients exposed to the intensive care unit or transplant units of a tertiary care hospital were infected with a multidrug-resistant strain of P. aeruginosa. All phenotypically similar isolates were examined for genetic relatedness by means of pulsed-field gel electrophoresis. Clinical characteristics of the affected patients were collected, and a detailed epidemiological and environmental investigation of potential sources was carried out. RESULTS Seventeen of the infected patients died within 3 months; for 12 (71%) of these patients, infection with the outbreak organism contributed to or directly caused death. The source of the outbreak was traced to hand hygiene sink drains, where biofilms containing viable organisms were found. Testing by use of a commercial fluorescent marker demonstrated that when the sink was used for handwashing, drain contents splashed at least 1 meter from the sink. Various attempts were made to disinfect the drains, but it was only when the sinks were renovated to prevent splashing onto surrounding areas that the outbreak was terminated. CONCLUSION This report highlights the importance of biofilms and of sink and patient room design in the propagation of an outbreak and suggests some strategies to reduce the risks associated with hospital sinks.

Influenza Vaccination of Healthcare Workers: Critical Analysis of the Evidence for Patient Benefit Underpinning Policies of Enforcement.

Background Four cluster randomized controlled trials (cRCTs) conducted in long-term care facilities (LTCFs) have reported reductions in patient risk through increased healthcare worker (HCW) influenza vaccination. This evidence has led to expansive policies of enforcement that include all staff of acute care hospitals and other healthcare settings beyond LTCFs. We critique and quantify the cRCT evidence for indirect patient benefit underpinning policies of mandatory HCW influenza vaccination. Methods Plausibility of the four cRCT findings attributing indirect patient benefits to HCW influenza vaccination was assessed by comparing percentage reductions in patient risk reported by the cRCTs to predicted values. Plausibly predicted values were derived according to the basic mathematical principle of dilution, taking into account HCW influenza vaccine coverage and the specificity of patient outcomes for influenza. Accordingly, predicted values were calculated as a function of relevant compound probabilities including vaccine efficacy (ranging 40–60% in HCWs and favourably assuming the same indirect protection conferred through them to patients) × change in proportionate HCW influenza vaccine coverage (as reported by each cRCT) × percentage of a given patient outcome (e.g. influenza-like illness (ILI) or all-cause mortality) plausibly due to influenza virus. The number needed to vaccinate (NNV) for HCWs to indirectly prevent patient death was recalibrated based on real patient data of hospital-acquired influenza, with adjustment for potential under-detection (5.2-fold), and using favourable assumptions of HCW-attributable risk (ranging 60–80%). Results In attributing patient benefit to increased HCW influenza vaccine coverage, each cRCT was found to violate the basic mathematical principle of dilution by reporting greater percentage reductions with less influenza-specific patient outcomes (i.e., all-cause mortality > ILI > laboratory-confirmed influenza) and/or patient mortality reductions exceeding even favourably-derived predicted values by at least 6- to 15-fold. If extrapolated to all LTCF and hospital staff in the United States, the prior cRCT-claimed NNV of 8 would implausibly mean >200,000 and >675,000 patient deaths, respectively, could be prevented annually by HCW influenza vaccination, inconceivably exceeding total US population mortality estimates due to seasonal influenza each year, or during the 1918 pandemic, respectively. More realistic recalibration based on actual patient data instead shows that at least 6000 to 32,000 hospital workers would need to be vaccinated before a single patient death could potentially be averted. Conclusions The four cRCTs underpinning policies of enforced HCW influenza vaccination attribute implausibly large reductions in patient risk to HCW vaccination, casting serious doubts on their validity. The impression that unvaccinated HCWs place their patients at great influenza peril is exaggerated. Instead, the HCW-attributable risk and vaccine-preventable fraction both remain unknown and the NNV to achieve patient benefit still requires better understanding. Although current scientific data are inadequate to support the ethical implementation of enforced HCW influenza vaccination, they do not refute approaches to support voluntary vaccination or other more broadly protective practices, such as staying home or masking when acutely ill.

Mandatory influenza vaccination? First we need a better vaccine

In light of the particularly severe 2012–2013 influenza season, great attention has been paid to influenza vaccination programs, including campaigns that target health care workers. In Canada, the vaccination of health care workers against influenza is almost exclusively voluntary; however,

Periprosthetic Infection following Primary Hip and Knee Arthroplasty: The Impact of Limiting the Postoperative Surveillance Period

BACKGROUND Hip and knee arthroplasty infections are associated with considerable healthcare costs. The merits of reducing the postoperative surveillance period from 1 year to 90 days have been debated. OBJECTIVES To report the first pan-Canadian hip and knee periprosthetic joint infection (PJI) rates and to describe the implications of a shorter (90-day) postoperative surveillance period. METHODS Prospective surveillance for infection following hip and knee arthroplasty was conducted by hospitals participating in the Canadian Nosocomial Infection Surveillance Program (CNISP) using standard surveillance definitions. RESULTS Overall hip and knee PJI rates were 1.64 and 1.52 per 100 procedures, respectively. Deep incisional and organ-space hip and knee PJI rates were 0.96 and 0.71, respectively. In total, 93% of hip PJIs and 92% of knee PJIs were identified within 90 days, with a median time to detection of 21 days. However, 11%-16% of deep incisional and organ-space infections were not detected within 90 days. This rate was reduced to 3%-4% at 180 days post procedure. Anaerobic and polymicrobial infections had the shortest median time from procedure to detection (17 and 18 days, respectively) compared with infections due to other microorganisms, including Staphylococcus aureus. CONCLUSIONS PJI rates were similar to those reported elsewhere, although differences in national surveillance systems limit direct comparisons. Our results suggest that a postoperative surveillance period of 90 days will detect the majority of PJIs; however, up to 16% of deep incisional and organ-space infections may be missed. Extending the surveillance period to 180 days could allow for a better estimate of disease burden. Infect Control Hosp Epidemiol 2017;38:147-153.

Longitudinal Multicenter Analysis of Outcomes After Cessation of Control Measures for Vancomycin-Resistant Enterococci.

OBJECTIVE To assess clinically relevant outcomes after complete cessation of control measures for vancomycin-resistant enterococci (VRE). DESIGN Quasi-experimental ecological study over 3.5 years. METHODS All VRE screening and isolation practices at 4 large academic hospitals in Ontario, Canada, were stopped on July 1, 2012. In total, 618 anonymized abstracted charts of patients with VRE-positive clinical isolates identified between July 1, 2010, and December 31, 2013, were reviewed to determine whether the case was a true VRE infection, a VRE colonization or contaminant, or a true VRE bacteremia. All deaths within 30 days of the last VRE infection were also reviewed to determine whether the death was fully or partially attributable to VRE. All-cause mortality was evaluated over the study period. Generalized estimating equation methods were used to cluster outcome rates within hospitals, and negative binomial models were created for each outcome. RESULTS The incidence rate ratio (IRR) for VRE infections was 0.59 and the associated P value was .34. For VRE bacteremias, the IRR was 0.54 and P=.38; for all-cause mortality the IRR was 0.70 and P=.66; and for VRE attributable death, the IRR was 0.35 and P=.49. VRE control measures were not significantly associated with any of the outcomes. Rates of all outcomes appeared to increase during the 18-month period after cessation of VRE control measures, but none reached statistical significance. CONCLUSION Clinically significant VRE outcomes remain rare. Cessation of all control measures for VRE had no significant attributable adverse clinical impact. Infect Control Hosp Epidemiol 2016;1-7.

The evolving epidemiology of Clostridium difficile infection in Canadian hospitals during a postepidemic period (2009-2015).

Background: The clinical and molecular epidemiology of health care–associated Clostridium difficile infection in nonepidemic settings across Canada has evolved since the first report of the virulent North American pulsed-field gel electrophoresis type 1 (NAP1) strain more than 15 years ago. The objective of this national, multicentre study was to describe the evolving epidemiology and molecular characteristics of health care–associated C. difficile infection in Canada during a post-NAP1-epidemic period, particularly patient outcomes associated with the NAP1 strain. Methods: Adult inpatients with C. difficile infection were prospectively identified, using a standard definition, between 2009 and 2015 through the Canadian Nosocomial Infection Surveillance Program (CNISP), a network of 64 acute care hospitals. Patient demographic characteristics, severity of infection and outcomes were reviewed. Molecular testing was performed on isolates, and strain types were analyzed against outcomes and epidemiologic trends. Results: Over a 7-year period, 20 623 adult patients admitted to hospital with health care–associated C. difficile infection were reported to CNISP, and microbiological data were available for 2690 patients. From 2009 to 2015, the national rate of health care–associated C. difficile infection decreased from 5.9 to 4.3 per 10 000 patient-days. NAP1 remained the dominant strain type, but infection with this strain has significantly decreased over time, followed by an increasing trend of infection with NAP4 and NAP11 strains. The NAP1 strain was significantly associated with a higher rate of death attributable to C. difficile infection compared with non-NAP1 strains (odds ratio 1.91, 95% confidence interval [CI] 1.29–2.82). Isolates were universally susceptible to metronidazole; one was nonsusceptible to vancomycin. The proportion of NAP1 strains within individual centres predicted their rates of health care–associated C. difficile infection; for every 10% increase in the proportion of NAP1 strains, the rate of health care–associated C. difficile infection increased by 3.3% (95% CI 1.7%–4.9%). Interpretation: Rates of health care–associated C. difficile infection have decreased across Canada. In nonepidemic settings, NAP4 has emerged as a common strain type, but NAP1, although decreasing, continues to be the predominant circulating strain and remains significantly associated with higher attributable mortality.