Point-prevalence surveys for infection or colonization with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae (CREs), and for Clostridium difficile infection (CDI) were conducted in Canadian hospitals in 2010 and 2012 to better understanding changes in the epidemiology of antimicrobial-resistant organisms (AROs), which is crucial for public health and care management.

A third survey of the same AROs in adult inpatients in Canadian hospitals with ≥50 beds was performed in February 2016. Data on participating hospitals and patient cases were obtained using standard criteria and case definitions. Associations between ARO prevalence and institutional characteristics were assessed using logistic regression models.

In total, 160 hospitals from 9 of the 10 provinces with 35,018 adult inpatients participated in the survey. Median prevalence per 100 inpatients was 4.1 for MRSA, 0.8 for VRE, 1.1 for CDI, 0.8 for ESBLs, and 0 for CREs. No significant change occurred compared to 2012. CREs were reported from 24 hospitals (15%) in 2016 compared to 10 hospitals (7%) in 2012. Routine universal or targeted admission screening for VRE decreased from 94% in 2010 to 74% in 2016. Targeted screening for MRSA on admission was associated with a lower prevalence of MRSA infection. Large hospitals (>500 beds) had higher prevalences of CDI.

This survey provides national prevalence rates for AROs in Canadian hospitals. Changes in infection control and prevention policies might lead to changes in the epidemiology of AROs and our capacity to detect them.

To measure transmission frequencies and risk factors for household acquisition of community-associated and healthcare-associated (HA-) methicillin-resistant Staphylococcus aureus (MRSA).

Prospective cohort study from October 4, 2008, through December 3, 2012.

Seven acute care hospitals in or near Toronto, Canada.

Total of 99 MRSA-colonized or MRSA-infected case patients and 183 household contacts.

Baseline interviews were conducted, and surveillance cultures were collected monthly for 3 months from household members, pets, and 8 prespecified high-use environmental locations. Isolates underwent pulsed-field gel electrophoresis and staphylococcal cassette chromosome mec typing.

Overall, of 183 household contacts 89 (49%) were MRSA colonized, with 56 (31%) detected at baseline. MRSA transmission from index case to contacts negative at baseline occurred in 27 (40%) of 68 followed-up households. Strains were identical within households. The transmission risk for HA-MRSA was 39% compared with 40% (P=.95) for community-associated MRSA. HA-MRSA index cases were more likely to be older and not practice infection control measures (P=.002–.03). Household acquisition risk factors included requiring assistance and sharing bath towels (P=.001–.03). Environmental contamination was identified in 78 (79%) of 99 households and was more common in HA-MRSA households.

Household transmission of community-associated and HA-MRSA strains was common and the difference in transmission risk was not statistically significant.

Infect Control Hosp Epidemiol 2016;1–7

Bloodstream infection (BSI) due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with considerable morbidity and mortality.

To determine the incidence of MRSA BSI in Canadian hospitals and to identify variables associated with increased mortality.

Prospective surveillance for MRSA BSI conducted in 53 Canadian hospitals from January 1, 2008, through December 31, 2012. Thirty-day all-cause mortality was determined, and logistic regression analysis was used to identify variables associated with mortality.

A total of 1,753 patients with MRSA BSI were identified (incidence, 0.45 per 1,000 admissions). The most common sites presumed to be the source of infection were skin/soft tissue (26.6%) and an intravascular catheter (22.0%). The most common spa types causing MRSA BSI were t002 (USA100/800; 55%) and t008 (USA300; 29%). Thirty-day all-cause mortality was 23.8%. Mortality was associated with increasing age (odds ratio, 1.03 per year [95% CI, 1.02–1.04]), the presence of pleuropulmonary infection (2.3 [1.4–3.7]), transfer to an intensive care unit (3.2 [2.1–5.0]), and failure to receive appropriate antimicrobial therapy within 24 hours of MRSA identification (3.2 [2.1–5.0]); a skin/soft-tissue source of BSI was associated with decreased mortality (0.5 [0.3–0.9]). MRSA genotype and reduced susceptibility to vancomycin were not associated with risk of death.

This study provides additional insight into the relative impact of various host and microbial factors associated with mortality in patients with MRSA BSI. The results emphasize the importance of ensuring timely receipt of appropriate antimicrobial agents to reduce the risk of an adverse outcome.

Infect. Control Hosp. Epidemiol. 2016;37(4):390–397

To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile infection (CDI) in Canadian hospitals.

National point prevalence survey in November 2010.

Canadian acute care hospitals with at least 50 beds.

Adult inpatients colonized or infected with MRSA or VRE or with CDI.

The prevalence (per 100 inpatients) of MRSA, VRE, and CDI was determined. Associations between prevalence and institutional characteristics and infection control policies were evaluated.

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]).

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.

An analysis of a cluster of New Delhi metallo-β-lactamase-l-producing Klebsiella pneumoniae (NDMl-Kp) and a retrospective case-cohort analysis of risk factors for acquisition in contacts of NDM1-Kp-positive patients.

A 1,100-bed Canadian academic tertiary care center.

Two index patients positive for NDMl-Kp as well as 45 contacts (roommates, ward mates, or environmental contacts) were investigated.

Retrospective chart reviews of all patients colonized or infected with NDM1-Kp as well as contacts of these patients were performed in order to describe the epidemiology and impact of infection prevention and control measures. A case-cohort analysis was conducted investigating 45 contacts of NDM1-Kp-positive patients to determine risk factors for acquisition of NDM1-Kp. Rectal swabs were screened for NDMl-Kp using chromogenic agar. Presence of blaNDM-1 was confirmed by multiplex polymerase chain reaction. Clonality was assessed with pulsed-field gel electrophoresis (PFGE) using restriction enzyme XbaI.

Two index cases carrying NDM1-Kp with different PFGE patterns were identified. Nosocomial transmission to 7 patients (4 roommates, 2 ward mates, and 1 environmental contact) was subsequenüy identified. Risk factors for acquisition of NDM1-Kp were a history of prior receipt of certain antibiotics (fluoroquinolones [odds ratio (OR), 16.8 (95% confidence interval [CI], 1.30-58.8); P = .005], trimethoprim-sulfamethoxazole [OR, 11.3 (95% CI, 1.84-70.0); P = .01], and carbapenems [OR, 16.8 (95% CI, 1.79-157.3); P = .04]) and duration of exposure to NDM1-Kp-positive roommates (26.5 vs 6.7 days; P< .001).

Two distinct clones of NDM1-Kp were transmitted to 7 inpatient contacts over several months. Implementation of contact precautions, screening of contacts for NDM1-Kp carriage, and attention to environmental disinfection contributed to the interruption of subsequent spread of the organism. The appropriate duration and frequency of screening contacts of NDMl-Kp-positive patients require further study.

To determine the effect of the rate and pattern of patient transfers among institutions within a single metropolitan area on the rates of methicillin-resistant Staphylococcus aureus (MRSA) transmission among patients in hospitals and nursing homes.

A stochastic, discrete-time, Monte Carlo simulation was used to model the rate and spread of MRSA transmission among patients in medical institutions within a single metropolitan area. Admission, discharges, transfers, and nosocomial transmission were simulated with respect to different interinstitutional transfer strategies and various situational scenarios, such as outlier institutions with high transmission rates.

The simulation results indicated that transfer patterns and transfer rate changes do not affect nosocomial MRSA transmission. Outlier institutions with high transmission rates affect the systemwide rate of nosocomial infections differently, depending on institution type.

It is worth effort to understanding disease-transmission dynamics and interinstitutional transfer patterns for the management of recently introduced diseases or strains. Once endemic in a system, other strategies for transmission control need to be implemented.

To determine the incidence and describe the changing epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection in Canadian hospitals from 1995–2007.

Forty-eight hospitals participating in the Canadian Nosocomial Infection Surveillance Program.

Prospective, laboratory-based surveillance for incident cases of MRSA colonization or infection among hospitalized patients.

Clinical and epidemiologic data were obtained by review of hospital records. Standard criteria were used to determine whether MRSA colonization or infection was present and whether the MRSA strain was healthcare associated or community associated. A representative subset of isolates was characterized by use of pulsed-field gel electrophoresis and staphylococcal cassette chromosome (SCC) mec typing.

From 1995 to 2007, a total of 37,169 hospitalized patients were newly identified as either infected or colonized with MRSA, and the overall incidence of both MRSA colonization and MRSA infection increased from 0.65 to 11.04 cases per 10,000 patient-days (P < .001). Of these 37,169 patients, 11,828 (32%) had an MRSA infection, and infection rate increased from 0.36 to 3.43 cases per 10,000 patient-days. The proportion of community-associated MRSA strains increased from 6% to 23% (P < .001). The most common genotype (47% of isolates) was CMRSA-2 (USA100/800); in 2007, CMRSA-10 (USA300) was the second most common strain (27% of isolates), associated with SCCmec type IV. Patients with CMRSA-10 were predominantly from western Canada and were more likely to be children (odds ratio [OR], 10.0 [95% confidence interval {CI}, 7.4–13.4]) and to have infection (OR, 2.3 [95% CI, 1.9–2.7]), especially skin and/or soft tissue infection (OR, 5.9 [95% CI, 5.0–6.9]).

The overall incidence of both MRSA colonization and MRSA infection increased 17-fold in Canadian hospitals from 1995 to 2007. There has also been a dramatic increase in cases of community-associated MRSA infection due to the CMRSA-10 (USA300) clone. Continued surveillance is needed to monitor the ongoing evolution of MRSA colonization or infection in Canada and globally.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), which is caused primarily by the Canadian methicillin-resistant Staphylococcus aureus-10 (CMRSA-10) strain (also known as the USA300 strain) has emerged rapidly in the United States and is now emerging in Canada. We assessed the prevalence, risk factors, microbiological characteristics and outcomes of CA-MRSA in patients with purulent skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs) in the Greater Toronto Area.

Patients with Staphylococcus aureus SSTIs who presented to 7 EDs between Mar. 1 and Jun. 30, 2007, were eligible for inclusion in this study. Antimicrobial susceptibilities and molecular characteristics of MRSA strains were identified. Demographic, risk factor and clinical data were collected through telephone interviews.

MRSA was isolated from 58 (19%) of 299 eligible patients. CMRSA-10 was identified at 6 of the 7 study sites and accounted for 29 (50%) of all cases of MRSA. Telephone interviews were completed for 161 of the eligible patients. Individuals with CMRSA-10 were younger (median 34 v. 63 yr, p = 0.002), less likely to report recent antibiotic use (22% v. 67%, p = 0.046) or health care–related risk factors (33% v. 72%, p = 0.097) and more likely to report community-related risk factors (56% v. 6%, p = 0.008) than patients with other MRSA strains. CMRSA-10 SSTIs were treated with incision and drainage (1 patient), antibiotic therapy (3 patients) or both (5 patients), and all resolved. CMRSA-10 isolates were susceptible to clindamycin, tetracycline and trimethoprimsulfamethoxazole.

CA-MRSA is a significant cause of SSTIs in the Greater Toronto Area, and can affect patients without known community-related risk factors. The changing epidemiology of CA-MRSA necessitates further surveillance to inform prevention strategies and empiric treatment guidelines.

To validate the National Nosocomial Infections Surveillance system risk index through administrative data to predict surgical site infections.

Retrospective cohort study.

Population-based analysis in Ontario, Canada.

All elderly patients who underwent elective surgery from April 1, 1992, through March 31, 2006 (n = 469,349).

Data on procedural and patient outcomes were gathered from linked population-wide hospital discharge records and physician claims. The 75th percentile of surgical duration was estimated through anesthesiologist billing fees recorded in 15-minute increments; the American Society of Anesthesiology score of at least 3 out of 5 was estimated by diagnostic codes for severe systemic illness; and all surgeries were classified as clean or clean-contaminated because of their elective nature (thus, the maximum score on the modified index was 2).

A total of 147,216 surgeries (31%) had a score of 0;246,592 (53%) had a score of 1; and 75,541 (16%) had a score of 2 on the modified index. The 30-day risk of surgical site infection increased with each increment in the modified index (score of 0, 5.4%; score of 1, 8.0%; score of 2, 14.3%; P < .001). The association was evident for surgical site infection diagnosed during the index admission (score of 0, 2.0%; score of 1, 3.7%; score of 2, 8.9%; P < .001), as well as that associated with reoperation or death (score of 0, 0.04%; score of 1, 0.23%; score of 2, 0.73%; P < .001). The modified index predicted increases in surgical site infection risk within each of 11 surgical subgroups. In accord with past research, the modified index had modest discrimination (C statistic, 0.59), and the majority of surgical site infections (72%) occurred within lower risk strata.

The modified index predicts surgical site infection in population-based analyses and is associated with incremental increases in risk.

To determine risk factors and outcomes associated with ciprofloxacin resistance in clinical bacterial isolates from intensive care unit (ICU) patients.

Prospective cohort study.

Twenty-bed medical-surgical ICU in a Canadian tertiary care teaching hospital.

All patients admitted to the ICU with a stay of at least 72 hours between January 1 and December 31, 2003.

Prospective surveillance to determine patient comorbidities, use of medical devices, nosocomial infections, use of antimicrobials, and outcomes. Characteristics of patients with a ciprofloxacin-resistant gram-negative bacterial organism were compared with characteristics of patients without these pathogens.

Ciprofloxacin-resistant organisms were recovered from 20 (6%) of 338 ICU patients, representing 38 (21%) of 178 nonduplicate isolates of gram-negative bacilli. Forty-nine percent of Pseudomonas aeruginosa isolates and 29% of Escherichia coli isolates were resistant to ciprofloxacin. In a multivariate analysis, independent risk factors associated with the recovery of a ciprofloxacin-resistant organism included duration of prior treatment with ciprofloxacin (relative risk [RR], 1.15 per day [95% confidence interval {CI}, 1.08-1.23]; P < .001), duration of prior treatment with levofloxacin (RR, 1.39 per day [95% CI, 1.01-1.91]; P = .04), and length of hospital stay prior to ICU admission (RR, 1.02 per day [95% CI, 1.01-1.03]; P = .005). Neither ICU mortality (15% of patients with a ciprofloxacin-resistant isolate vs 23% of patients with a ciprofloxacin-susceptible isolate; P = .58 ) nor in-hospital mortality (30% vs 34%; P = .81 ) were statistically significantly associated with ciprofloxacin resistance.

ICU patients are at risk of developing infections due to ciprofloxacin-resistant organisms. Variables associated with ciprofloxacin resistance include prior use of fluoroquinolones and duration of hospitalization prior to ICU admission. Recognition of these risk factors may influence antibiotic treatment decisions.

To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistant Staphylococcus aureus (MRSA) transmission among hospitalized patients.

General medical ward.

Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs.

The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened.

Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission. (Infect Control Hosp Epidemiol 2005;26:607- 615)

The four hospitals assessed in this study use active surveillance cultures for methicillin-resistant Staphylococcus aureus (MRSA) and contact precautions for MRSA-positive patients as part of routine infection control practices. The objective of this study was to determine whether nosocomial acquisition of MRSA decreased in these hospitals during an outbreak of severe acute respiratory syndrome (SARS) when barrier precautions were routinely used for all patients.

Retrospective cohort study.

Three tertiary-care hospitals (a 1,100-bed hospital; a 500-bed hospital; and an 823-bed hospital) and a 430-bed community hospital, each located in Toronto, Ontario, Canada.

All admitted patients were included.

The nosocomial rate of MRSA in all four hospitals combined during the SARS outbreak (3.7 per 10,000 patient-days) was not significantly different from that before (4.7 per 10,000 patient-days) or after (3.4 per 10,000 patient-days) the outbreak (P = .30 and P = .76, respectively). The nosocomial rate of MRSA after the outbreak was significantly lower than that before the outbreak (P = .003). Inappropriate reuse of gloves and gowns and failure to wash hands between patients on non-SARS wards were observed during the outbreak. Increased attention was paid to infection control education following the outbreak.

Inappropriate reuse of gloves and gowns and failure to wash hands between patients may have contributed to transmission of MRSA during the SARS outbreak. Attention should be paid to training healthcare workers regarding the appropriate use of precautions as a means to protect themselves and patients.

Antiviral prophylaxis is recommended for the control of institutional influenza A outbreaks. In long-term–care institutions other than nursing homes, neither the seriousness of influenza nor the risks and benefits of antiviral prophylaxis is clearly understood. We studied the severity of illness due to influenza among adults residing in a center for the developmentally disabled and assessed adverse reactions to amantadine and oseltamivir prophylaxis.

Data were collected from the charts of consenting residents. Complications of upper respiratory tract illness were recorded. Potential adverse events were documented during amantadine and oseltamivir therapy, and during a baseline period with neither medication.

The median age of the 287 participants was 46.4 years. Only 15 (5%) were older than 65 years, and 69 (24%) had chronic underlying medical illness placing them at high risk for influenza. Of the 122 residents with an upper respiratory tract infection, 16 (13%) developed pneumonia, 12 (9.8%) were hospitalized, and 5 (4%) died. Twenty-eight (25%) of 112 residents had an adverse neurologic event while receiving amantadine prophylaxis, compared with 3 (2.7%) receiving no antiviral medication and 5 (4.5%) receiving oseltamivir (P < .001). Sixteen percent of the residents discontinued amantadine due to adverse events; in contrast, adverse events were identified in 2.9% of the residents prescribed oseltamivir, and none discontinued therapy.

Viral respiratory tract infections are associated with a high risk of complications in this population. The rate of adverse neurologic events associated with amantadine was significantly higher than that associated with oseltamivir.