Prevalence of antibiotic-resistant organisms in Canadian Hospitals. Comparison of point-prevalence survey results from 2010, 2012, and 2016.

OBJECTIVE: Point-prevalence surveys for infection or colonization with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended-spectrum ß-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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Indeterminate tcdB using a Clostridium difficile PCR assay: a retrospective cohort study.

BACKGROUND: C. difficile (CD) real-time polymerase chain reaction (PCR) for toxin B gene (tcdB) is more sensitive, and reduces turnaround time when compared to toxin immunoassay. We noted typical amplification curves with high tcdB cycle thresholds (Ct) and low endpoints (Ept) that are labeled negative by the Xpert(®) C. difficile assay (Cepheid) and undertook this study to determine their significance. METHODS: We defined an indeterminate CD assay result as detection of a typical PCR amplification curve with an Ept >10 that was interpreted as negative by the Xpert(®) assay. Samples with indeterminate Xpert(®) result were collected for 5 months and retested by Xpert(®), cultured for toxigenic CD, and isolates subjected to PCR ribotyping, detection of toxin genes and multilocus variable-number tandem repeat analysis (MLVA) typing. Chart reviews were completed to assess if patients met the Society of Healthcare Epidemiology of America and the Infectious Diseases Society of America CD infection (CDI) clinical case definition. Illness severity was compared with tcdB Ct and culture results. RESULTS: During the 5-month study period, 48/3620 (1%) of specimens were indeterminate and 387/3620 (11%) were positive. Of the 48 patients with indeterminate results, 39 (81%) met the clinical case definition of CDI, and 7 of these (18%) met criteria for severe CDI. Toxigenic stool cultures were positive for 86% (6/7) of patients with severe CDI, 19% (6/32) of patients with non-severe CDI, and 44% (4/9) of patients who did not meet the clinical case definition of CDI (p = 0.002). Lower tcdB Ct and higher Ept were associated with greater likelihood of toxigenic culture positivity (p = 0.03) and more severe symptoms (p = 0.06). Indeterminate results were not associated with a particular technologist or instrument module, or CD strain type. CONCLUSIONS: A subset of specimens (1%) using the Xpert(®) C. difficile assay have typical amplification curves and are interpreted as negative. At least one-third of these results are associated with positive CD culture. The mechanism of these indeterminate results is not technique-related, equipment-related, or due to particular CD strains. Clinicians should be aware that even PCR testing has the potential to miss CDI cases and further highlights the importance of clinical context when interpreting results.

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.

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.

Risk factors for and outcomes associated with clinical isolates of Escherichia coli and Klebsiella species resistant to extended-spectrum cephalosporins among patients admitted to Canadian hospitals.

BACKGROUND: Clinical features associated with Gram-negative bacterial isolates with extended-spectrum beta-lactamase (ESBL)- and AmpC-mediated resistance identified in Canadian hospitals is largely unknown. The objective of the present study was to determine the demographics, risk factors and outcomes of patients with ESBL- or AmpC-mediated resistant organisms in Canadian hospitals. METHODS: Patients with clinical cultures of Escherichia coli or Klebsiella species were matched with patients with a similar organism but susceptible to third-generation cephalosporins. Molecular identification of the AmpC or ESBL was determined using a combination of polymerase chain reaction and sequence analysis. Univariate and multivariate logistic regression analysis was performed to identify variables associated with becoming a case. RESULTS: Eight Canadian hospitals identified 106 cases (ESBL/AmpC) and 106 controls. All risk factors identified in the univariate analysis as a predictor of being an ESBL/AmpC cases at the 0.20 P-value were included in the multivariate analysis. No significant differences in outcomes were observed (unfavourable responses 17% versus 15% and mortality rates 13% versus 7%, P not significant). Multivariate logistic regression found an association of becoming an ESBL/AmpC case with: previous admission to a nursing home (OR 8.28, P=0.01) or acute care facility (OR 1.96, P=0.03), length of stay before infection (OR 3.05, P=0.004), and previous use of first-generation cephalosporins (OR 2.38, P=0.02) or third-generation cephalosporins (OR 4.52, P=0.01). Appropriate antibiotics were more likely to be given to controls (27.0% versus 13.3%, P=0.05) and number of days to appropriate antibiotics was longer for cases (median 2.8 days versus 1.2 days, P=0.05). CONCLUSION: The importance of patient medical history, present admission and antibiotic use should be considered for all E coli or Klebsiella species patients pending susceptibility testing results.

Transmission of influenza A in human beings.

Planning for the next influenza pandemic is occurring at many levels throughout the world, spurred on by the recent spread of H5N1 avian influenza in Asia, Europe, and Africa. Central to these planning efforts in the health-care sector are strategies to minimise the transmission of influenza to health-care workers and patients. The infection control precautions necessary to prevent airborne, droplet, and contact transmission are quite different and will need to be decided on and planned before a pandemic occurs. Despite vast clinical experience in human beings, there continues to be much debate about how influenza is transmitted. We have done a systematic review of the English language experimental and epidemiological literature on this subject to better inform infection control planning efforts. We have found that the existing data are limited with respect to the identification of specific modes of transmission in the natural setting. However, we are able to conclude that transmission occurs at close range rather than over long distances, suggesting that airborne transmission, as traditionally defined, is unlikely to be of significance in most clinical settings. Further research is required to better define conditions under which the influenza virus may transmit via the airborne route.

Contamination of bone marrow products with an actinomycete resembling Microbacterium species and reinfusion into autologous stem cell and bone marrow transplant recipients.

Bacterial contamination of bone marrow or peripheral blood stem cell transplant products typically occurs with skin flora or, rarely, gram-negative organisms. We describe a clonal outbreak of contamination in transplant products caused by contamination with an aerobic actinomycete that occurred at our institution during the summer of 2001. From 1 July through 12 September 2001, 73 peripheral blood or bone marrow stem cell products were obtained from 39 patients, and 34 products were found to be contaminated with the outbreak strain. Fourteen patients were reinfused with contaminated cells, and the outbreak strain was isolated from the blood cultures for one patient. Investigation revealed multiple potential sources for contamination during the product cryopreservation process. The outbreak of contamination was aborted upon modification of the cryopreservation process.