Victoria Williams

The Role of Colonization Pressure in Nosocomial Transmission of Methicillin Resistant Staphylococcus aureus

BACKGROUND Colonized or infected patients are a major reservoir for patient-to-patient transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals. Despite attempted adherence to recommended infection prevention and control procedures, a general medicine unit in our hospital continued to experience ongoing transmission of MRSA. The role that colonization pressure (CP) plays in nosocomial transmission of MRSA on a general medicine unit was assessed, and a threshold CP above which additional IP&C practices should be implemented was proposed. METHODS From January 2005 to December 2006, all patients admitted to a 36-bed general medicine unit were screened on admission for MRSA. Monthly MRSA nosocomial incidence (new nosocomial cases x 1000/susceptible patient-days) and CP (number of MRSA patient-days x 100/total patient-days) were calculated. The relative risk (RR) of MRSA transmission above and below the median CP with 95% confidence interval was calculated. RESULTS Twenty-one cases of nosocomially acquired MRSA were detected during the study period, with transmission occurring in 8 separate months. The median CP during the 2 years was 6.7%. The RR of MRSA acquisition increased as CP increased above the median (RR, 7.6; 95% CI: 1.1-52.6; P = .008). MRSA outbreaks were declared on 2 separate occasions, and, in each, the CP for the preceding month was greater than the median value of 6.7%. CONCLUSION CP has a significant effect on the subsequent transmission of MRSA on a general medicine unit. Ongoing monitoring of CP provides the opportunity for early implementation of enhanced infection prevention and control practices and can potentially decrease nosocomial transmission of MRSA and prevent outbreaks.

Epidemiology and Outcome of Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus (MRSA) in Canadian Hospitals

Background MRSA remains a leading cause of hospital-acquired (HAP) and healthcare-associated pneumonia (HCAP). We describe the epidemiology and outcome of MRSA pneumonia in Canadian hospitals, and identify factors contributing to mortality. Methods Prospective surveillance for MRSA pneumonia in adults was done for one year (2011) in 11 Canadian hospitals. Standard criteria for MRSA HAP, HCAP, ventilator-associated pneumonia (VAP), and community-acquired pneumonia (CAP) were used to identify cases. MRSA isolates underwent antimicrobial susceptibility testing, and were characterized by pulsed-field gel electrophoresis (PFGE) and Panton-Valentine leukocidin (PVL) gene detection. The primary outcome was all-cause mortality at 30 days. A multivariable analysis was done to examine the association between various host and microbial factors and mortality. Results A total of 161 patients with MRSA pneumonia were identified: 90 (56%) with HAP, 26 (16%) HCAP, and 45 (28%) CAP; 23 (14%) patients had VAP. The mean (± SD) incidence of MRSA HAP was 0.32 (± 0.26) per 10,000 patient-days, and of MRSA VAP was 0.30 (± 0.5) per 1,000 ventilator-days. The 30-day all-cause mortality was 28.0%. In multivariable analysis, variables associated with mortality were the presence of multiorgan failure (OR 8.1; 95% CI 2.5-26.0), and infection with an isolate with reduced susceptibility to vancomycin (OR 2.5, 95% CI 1.0-6.3). Conclusions MRSA pneumonia is associated with significant mortality. Severity of disease at presentation, and infection caused by an isolate with elevated MIC to vancomcyin are associated with increased mortality. Additional studies are required to better understand the impact of host and microbial variables on outcome.

Prevalence of colonization and infection with methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus and of Clostridium difficile infection in Canadian hospitals.

OBJECTIVE To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile infection (CDI) in Canadian hospitals. DESIGN National point prevalence survey in November 2010. SETTING Canadian acute care hospitals with at least 50 beds. PATIENTS Adult inpatients colonized or infected with MRSA or VRE or with CDI. METHODS The prevalence (per 100 inpatients) of MRSA, VRE, and CDI was determined. Associations between prevalence and institutional characteristics and infection control policies were evaluated. RESULTS One hundred seventy-six hospitals (65% of those eligible) participated. The median (range) prevalence rates for MRSA and VRE colonization or infection and CDI were 4.2% (0%-22.1%), 0.5% (0%-13.1%), and 0.9% (0%-8.6%), respectively. Median MRSA and VRE infection rates were low (0.3% and 0%, respectively). MRSA, VRE, and CDI were thought to have been healthcare associated in 79%, 96%, and 84% of cases, respectively. In multivariable analysis, routine use of a private room for colonized/infected patients was associated with lower median MRSA infection rate (prevalence ratio [PR], 0.44 [95% confidence interval (CI), 0.22-0.88]) and VRE prevalence (PR, 0.26 [95% CI, 0.12-0.57]). Lower VRE rates were also associated with enhanced environmental cleaning (PR, 0.52 [95% CI, 0.36-0.75]). Higher bed occupancy rates were associated with higher rates of CDI (PR, 1.02 [95% CI, 1.01-1.03]). CONCLUSIONS These data provide the first national prevalence estimates for MRSA, VRE, and CDI in Canadian hospitals. Certain infection prevention and control policies were found to be associated with prevalence and deserve further investigation.

THE IMPACT OF TREATMENT MODALITY ON INFECTION-RELATED HOSPITALIZATION RATES IN PERITONEAL DIALYSIS AND HEMODIALYSIS PATIENTS

♦ Background and Objectives: Infection is a major cause of morbidity and mortality in the dialysis population. This study compares the rates of infection-related hospitalization (IRH) in incident chronic dialysis patients initiating outpatient peritoneal dialysis (PD) and hemodialysis (HD). ♦ Methods and Patients: This was a retrospective cohort study at the dialysis program of a tertiary-care center in Toronto, Canada. Incident chronic dialysis patients that were eligible for both PD and HD and started outpatient dialysis between 1 January 2004 and 31 August 2008 were included. Dialysis modality was assigned at the start of outpatient dialysis treatment. All hospital admissions were reviewed and incidence of IRH was compared between PD and HD using Poisson regression. ♦ Results: Of 264 incident chronic dialysis patients, 168 (64%) were eligible for both treatment modalities: 71 (42%) started outpatient PD and 97 (58%) started outpatient HD. The unadjusted and adjusted incidence rate ratios (IRR) of IRH did not differ significantly between PD and HD: 1.23 [95% confidence interval (CI) 0.65 – 2.32, p = 0.37] and 1.14 (95% CI 0.58 – 2.23, p = 0.71) respectively. There was no difference between PD and HD in the risk of access loss (28% vs 35%, p = 0.73), modality change (22% vs 0%, p = 0.10), or death (17% vs 6%, p = 0.60) following hospitalization for infection. Patients starting outpatient treatment on PD versus HD were more likely to be hospitalized for peritonitis (IRR 3.20, 95% CI 1.16 – 9.09; p = 0.029) and there was a trend for fewer hospitalizations for bacteremia (IRR 0.19, 95% CI 0.028 – 1.30; p = 0.091). The risk of IRH did not differ between PD and HD in the subgroup of patients that received adequate predialysis care (IRR 1.16, 95% CI 0.59 – 2.27; p = 0.67) or when patients starting outpatient HD with a central venous catheter were excluded (IRR 1.52, 95% CI 0.53 – 4.37; p = 0.44). ♦ Conclusions: Patients that initiate outpatient peritoneal dialysis do not have a significantly increased risk of infection-related hospitalization compared to those that initiate outpatient hemodialysis.

Reducing the risk of severe complications among patients with Clostridium difficile infection

BACKGROUND The incidence and severity of Clostridium difficile infections are increasing, and there is a need to optimize the prevention of complicated disease. OBJECTIVE To identify modifiable processes of care associated with an altered risk of C difficile complications. METHODS A retrospective cohort study (with prospective case ascertainment) of all C difficile infections during 2007⁄2008 at a tertiary care hospital was conducted. RESULTS Severe complications were frequent (occurring in 97 of 365 [27%] C difficile episodes), with rapid onset (median three days postdiagnosis). On multivariable analysis, nonmodifiable predictors of complications included repeat infection (OR 2.67), confusion (OR 2.01), hypotension (OR 0.97 per increased mmHg) and elevated white blood cell count (OR 1.04 per 109 cells⁄L). Protection from complications was associated with initial use of vancomycin (OR 0.24); harm was associated with ongoing use of exacerbating antibiotics (OR 3.02). CONCLUSION C difficile infections often occur early in the disease course and are associated with high complication rates. Clinical factors that predicted a higher risk of complications included confusion, hypotension and leukocytosis. The most effective ways to improve outcomes for patients with C difficile colitis are consideration of vancomycin as first-line treatment for moderate to severe cases, and the avoidance of unnecessary antibiotics.

Is the prevalence of antibiotic-resistant organisms changing in Canadian hospitals? Comparison of point-prevalence survey results in 2010 and 2012

A national point-prevalence survey for infection or colonization with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), and for Clostridium difficile infection (CDI) was done in Canadian hospitals in 2010. A follow-up survey was done in November 2012 to determine whether there were any changes in the prevalence of these organisms; we also determined the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, and carbapenem-resistant Enterobacteriaceae (CREs). Associations between prevalence and infection prevention and control policies were evaluated in logistic regression models. A total of 143 (67% of eligible facilities) hospitals with 29 042 adult inpatients participated in the survey, with representation from all 10 provinces; 132 hospitals participated in 2010 and 2012. There were no significant changes in the median prevalence of MRSA in 2010 (4.3%) compared to 2012 (3.9%), or of CDI in 2010 (0.8%) compared to 2012 (0.9%). A higher median prevalence of VRE was identified in 2012 (1.3%) compared to 2010 (0.5%) (p 0.04), despite decreased VRE screening in 2012. The median prevalence of ESBLs was 0.7% and was 0 for CREs; CREs were reported from only 10 hospitals (7.0%). A policy of routinely caring for patients with MRSA or VRE in a private isolation room was associated with lower prevalence of these organisms. Targeted screening of high-risk patients at admission was associated with lower MRSA prevalence; better hand hygiene compliance was associated with lower VRE prevalence. These data provide national prevalence rates for antibiotic-resistant organisms among adults hospitalized in Canadian hospitals. Certain infection prevention and control policies were associated with prevalence.

Risk factors for Staphylococcus aureus surgical site infection during an outbreak in patients undergoing cardiovascular surgery.

BACKGROUND This study examined the epidemiology of an outbreak of Staphylococcus aureus surgical site infections (SSI) after cardiovascular surgery, and analyzed risk factors for S aureus SSIs. METHODS This was a retrospective case-control study to determine risk factors for S aureus SSI in 38 patients who developed S aureus SSI during the outbreak period, compared with age-, sex-, and procedure-matched controls. S aureus strains were typed by pulsed-field gel electrophoresis. RESULTS A total of 38 patients had S aureus SSI. Pulsed-field gel electrophoresis identified transmission of 3 S aureus clones (2 MSSA clones and 1 MRSA clone). Twenty-one health care workers were carriers of outbreak strains. In multivariate analysis, the significant risk factors for S aureus SSI were previous cardiac surgery (odds ratio, 7.41; 95% confidence interval, 1.05-52.16) and long procedure duration (odds ratio, 1.49; 95% confidence interval, 1.00-2.21). CONCLUSIONS This outbreak demonstrates evidence of nosocomial transmission of 3 clones of S aureus in the setting of incomplete compliance with recommended standard perioperative infection control measures, associated with a high prevalence of staff carriage of the predominant outbreak strains.

Acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in contacts of patients newly identified as colonized or infected with MRSA in the immediate postexposure and postdischarge periods

HighlightsThe proportion of contacts with follow‐up screening positive for methicillin‐resistant Staphylococcus aureus is small.The positivity rate for methicillin‐resistant Staphylococcus aureus contacts decreases over time from exposure.Some contacts may acquire methicillin‐resistant Staphylococcus aureus because of a subsequent new exposure. &NA; The acquisition of methicillin‐resistant Staphylococcus aureus (MRSA) after exposure to patients colonized or infected with MRSA was assessed. Among contacts with complete surveillance screening, the rate of acquisition was 5.7% and was lower in those identified postdischarge (17/683, 2.5%) compared with those tested in the immediate postexposure period (62/706, 8.8%).

902Hospital Characteristics and Infection Prevention and Control Strategies Associated with Methicillin-Resistant Staphylococcus aureus (MRSA) and Clostridium difficile Infection (CDI) in Canadian Hospitals

Strategies Associated with Methicillin-Resistant Staphylococcus aureus (MRSA) and Clostridium difficile Infection (CDI) in Canadian Hospitals Victoria Williams, BSc, BASc, MPH, CIC; Andrew E. Simor, MD, FRCPC, FACP; Alex Kiss, PhD; Allison Mcgeer, MD, MSc, FRCPC; Guanghong Han, PhD; Zahir Hirji, MSc; Oscar E. Larios, MD; Christine Moore, BSc, MLT; Karl Weiss, MD, MSc, FRCPC; Infection Prevention and Control Canada; Sunnybrook Health Sciences Centre Toronto, ON, Canada; Institute of Clinical Evaluative Sciences, Toronto, ON, Canada; Mount Sinai Hospital, Toronto, ON, Canada; Provincial Infection Control Network of British Columbia, Vancouver, BC, Canada; The Scarborough Hospital, Toronto, ON, Canada; University of Calgary, Calgary, AB, Canada; Hôpital Maisonneuve-Rosemont, Montreal, QC, Canada

Surveillance for Carbapenem Resistant Gram-Negative Bacilli in a Large Tertiary Care Centre

Issue: Multi-Drug Resistant Organisms (MDROs) are increasing in US hospitals at an alarming rate and our organization saw increasing numbers of patients with history of an MDRO. In 2009, our academic teaching facility organized a task force to address National Patient Safety Goal (NPSG).07.03.01 and to implement evidenced based practices to prevent healthcare associated infections due to MDROs in our patients.