Sociodemographic and geospatial associations with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in a large Canadian city: an 11 year retrospective study.

BACKGROUND: The first Canadian outbreak of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was identified in 2004 in Calgary, Alberta. Using a novel model of MRSA population-based surveillance, sociodemographic risk associations, yearly geospatial dissemination and prevalence of CA-MRSA infections over an 11 year period was identified in an urban healthcare jurisdiction of Calgary. METHODS: Positive MRSA case records, patient demographics and laboratory data were obtained from a centralized Laboratory Information System of Calgary Laboratory Services in Calgary, Alberta, Canada between 2004 and 2014. Public census data was obtained from Statistics Canada, which was used to match with laboratory data and mapped using Geographic Information Systems. RESULTS: During the study period, 52.5% of positive MRSA infections in Calgary were CA-MRSA cases. The majority were CMRSA10 (USA300) clones (94.1%; n = 4255), while the remaining case (n = 266) were CMRSA7 (USA400) clones. Period prevalence of CMRSA10 increased from 3.6 cases/100000 population in 2004, to 41.3 cases/100000 population in 2014. Geospatial analysis demonstrated wide dissemination of CMRSA10 annually in the city. Those who are English speaking (RR = 0.05, p <  0.0001), identify as visible minority Chinese (RR = 0.09, p = 0.0023) or visible minority South Asian (RR = 0.25, p = 0.015), and have a high median household income (RR = 0.27, p <  0.0001) have a significantly decreased relative risk of CMRSA10 infections. CONCLUSIONS: CMRSA10 prevalence increased between 2004 and 2007, followed by a stabilization of cases by 2014. Certain sociodemographic factors were protective from CMRSA10 infections. The model of MRSA population-surveillance and geomap outbreak events can be used to track the epidemiology of MRSA in any jurisdiction.

Molecular Evolution of a Klebsiella pneumoniae ST278 Isolate Harboring blaNDM-7 and Involved in Nosocomial Transmission.

During 2013, ST278 Klebsiella pneumoniae with blaNDM-7 was isolated from the urine (KpN01) and rectum (KpN02) of a patient in Calgary, Canada. The same strain (KpN04) was subsequently isolated from another patient in the same unit. Interestingly, a carbapenem-susceptible K. pneumoniae ST278 (KpN06) was obtained 1 month later from the blood of the second patient. Next-generation sequencing (NGS) revealed that the loss of carbapenem-resistance in KpN06 was due to a 5-kb deletion on the blaNDM-7-harboring IncX3 plasmid. In addition, an IncFIB plasmid in KpN06 had a 27-kb deletion that removed genes encoding for heavy metal resistance. Phylogenetic analysis showed that the K. pneumoniae ST278 from patient 2 was likely a descendant of KpN02 and that KpN06 was a close progenitor of an environmental ST278. It is unclear whether KpN06 lost the blaNDM-7 gene in vivo. This study detailed the remarkable plasticity and speed of evolutionary changes in multidrug-resistant K. pneumoniae, demonstrating the highly recombinant nature of this species. It also highlights the ability of NGS to clarify molecular microevolutionary events within antibiotic-resistant organisms.

The persisting burden of invasive pneumococcal disease in HIV patients: an observational cohort study.

BACKGROUND: The increasing use of highly active antiretroviral therapy (HAART) and pneumococcal immunization along with shifting community exposures may have altered the burden of Streptococcus pneumoniae disease in HIV-infected persons. We describe the burden and risk factors for pneumococcal disease in the modern era of HIV care and evaluate the use of a 23-valent pneumococcal polysaccharide vaccine (PPV-23). METHODS: The incidence of invasive pneumococcal disease (IPD) between January 1st, 2000 and January 1st, 2010 in a regional HIV population in Southern Alberta, Canada was determined by linking comprehensive laboratory and hospital surveillance data. Clinical and epidemiologic data including risk factors for S. pneumoniae, history of pneumococcal immunization, serotypes of infections, and length of any hospitalizations for pneumococcal disease were evaluated with multivariate analysis. CD4 count and viral load at immunization were evaluated with a nested case-control analysis. RESULTS: In 1946 HIV-patients with 11,099 person-years of follow up, there were 68 distinct episodes of pneumococcal disease occurring in 50 patients. Increased risk was seen if female, age >60, Aboriginal ethnicity, lower education, injection drug use, smoking, nadir CD4 <200/µL, chronic obstructive pulmonary disease, and hepatitis C. Overall, the incidence of IPD was 342/100,000 person-years and was reduced to 187/100,000 within three years of PPV-23 immunization (P < 0.01). Although 78% of patients received PPV-23, 74% of IPD episodes were caused by PPV-23 serotypes. In a case-control analysis, HIV viral load at immunization was significantly predictive of PPV-23 failure, while CD4 count was not. 80% of IPD cases required hospitalization: median length of stay was 7 days (range: 1-71); four patients died. CONCLUSIONS: Despite universal access to intensive measures to prevent pneumococcal disease including the widespread use of HAART and PPV-23 immunization, the incidence of IPD remains high in HIV patients with its associated morbidity and mortality.

Molecular analysis of Clostridium difficile PCR ribotype 027 isolates from Eastern and Western Canada.

The prevalence and characteristics of PCR ribotype 027 strains of Clostridium difficile have come into question following recent outbreaks in Eastern Canada and elsewhere. In order to determine the distribution of this strain in other regions in Canada, we screened a bank of 1,419 isolates recovered from three different Canadian health regions between 2000 and 2004. Among isolates from a Montreal area hospital, PCR ribotype 027 strains represented 115/153 strains (75.2%) from 2003 to 2004, but ribotype 027 strains were absent in 2000 and 2001. In Calgary, by contrast, ribotype 027 rates have remained relatively stable over 4 years of surveillance, representing 51/685 (7.4%) hospital isolates and 62/373 (16.6%) strains from the community (P < 0.001). PCR ribotype 027 accounted for 8/135 (5.9%) hospital isolates in the Fraser Health Region in 2004. repetitive extragenic palindromic PCR was used to subtype a random selection of 027 isolates from each region. All 10 of the isolates from Quebec were of a single subtype, which was also dominant among isolates from Alberta (8/10 isolates) and British Columbia (6/8 isolates). Comparative sequencing of the tcdC repressor gene confirmed the documented 18-bp deletion and identified a second, single-base-pair deletion at position 117. Both deletions were conserved across all three provinces and were identified in a United Kingdom reference strain. The presence of a frameshift in the early portion of the tcdC gene implies serious functional disruption and may contribute to the hypervirulence of the 027 phenotype. PCR ribotype 027 strains appear to be widely distributed, to predate the Montreal outbreak, and to have measurable community presence in Western Canada.