Dan Gregson

Molecular Analysis of Clostridium difficile PCR Ribotype 027 Isolates from Eastern and Western Canada

ABSTRACT 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.

Outbreak in Alberta of community-acquired (USA300) methicillin-resistant Staphylococcus aureus in people with a history of drug use, homelessness or incarceration

Background: The USA300 strain of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) can cause severe infection and is increasingly recognized as a cause of community outbreaks. In 2004, an outbreak was identified in the Calgary Health Region (CHR). Methods: MRSA isolates were identified with standard methods at a central regional laboratory and typed via pulsed-field gel electrophoresis (PFGE). Isolates were tested by PCR for mecA, Panton–Valentine leukocidin (PVL), SCCmec, and spa genes. Cases were defined as such if a clinical isolate of the USA300 strain was noted between January 1 and September 30, 2004, and the patient had lived or traveled in CHR within 2 years before symptom onset. Demographic, clinical and risk data on all such cases were collected from several sources for statistical analysis. A case was defined as high-risk if the patient had a history of drug use, homelessness or incarceration. Results: Of 40 isolates with the USA300 PFGE pattern, all tested positive for PVL, SCCmec type IVa and spa type 008. Almost all infections (39/40, 98%) involved skin and soft tissues, except for 1 death from necrotizing hemorrhagic pneumonia; a notable proportion (38%) required hospital admission or intravenous antimicrobial therapy. The outbreak centred on the high-risk population in CHR (70%; risk ratio 169.4, 95% confidence interval 86.1–333.0). Interpretation: People with histories of illicit drug use, homelessness or recent incarceration were at highest risk for infection with CA-MRSA. The emergence and spread of this virulent strain has important implications for treatment and public health in Canada.

Association between Handling of Pet Treats and Infection with Salmonella enterica Serotype Newport Expressing the AmpC β-Lactamase, CMY-2

ABSTRACT Resistance to the extended-spectrum cephalosporins can occur in Salmonella species via the production of extended-spectrum and AmpC β-lactamases. We describe human infections with Salmonella enterica serotype Newport phage type 14 strains resistant to ceftazidime (CAZ) and cefoxitin (FOX) related to the handling of pet treats containing dried beef. These strains were isolated from five patients in Calgary, Alberta, Canada, during 2002 and were compared to a strain cultured from a commercial pet treat present at the property of one of the patients. The strains were resistant to FOX, CAZ, cefpodoxime, ampicillin, and chloramphenicol; intermediate resistant to ceftriaxone and cefotaxime; and sensitive to the aminoglycosides, ciprofloxacin, cefepime, and imipenem. Isoelectric focusing, multiplex PCR, and sequencing of the amplicons showed that all strains produced the plasmid-encoded AmpC β-lactamase, CMY-2. Restriction analysis of plasmid DNA following transformation demonstrated that blaCMY-2 was encoded on an approximately 140-kb plasmid. Pulsed-field gel electrophoresis showed the human and pet treat Salmonella strains to be highly related. This study is the first to implicate the transfer of multidrug-resistant Salmonella species through the handling of commercial pet treats containing animal products. In addition to documenting the first cases of human infection caused by CMY-2-producing S. enterica serotype Newport strains in Canada, this study illustrates the necessity of rapid and accurate laboratory-based surveillance in the identification of novel types of antimicrobial resistance.

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

BackgroundThe 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).MethodsThe 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.ResultsIn 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.ConclusionsDespite 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.

Prevalence of USA300 Colonization or Infection and Associated Variables During an Outbreak of Community-Associated Methicillin-Resistant Staphylococcus aureus in a Marginalized Urban Population

BACKGROUNDnIn 2004, an outbreak of the USA300 strain of methicillin-resistant Staphylococcus aureus (MRSA) was identified in persons with histories of homelessness, illicit drug use or incarceration in the Calgary Health Region (Calgary, Alberta). A prevalence study was conducted to test the hypotheses for factors associated with USA300 colonization or infection.nnnMETHODSnParticipants were recruited at sites accessed by this marginalized population. Health care staff administered a questionnaire and collected crack pipes and nasal, axillary and skin infection swabs. Pipes and swabs were cultured according to standard techniques. MRSA isolates were further characterized by polymerase chain reaction (mecA, Panton-Valentine leukocidin and Staphylococcal cassette chromosome mec) and typing methods (pulsed-field gel electrophoresis, staphylococcal protein A typing and multilocus sequence typing). Colonization or infection was determined by having any one of nasal, axillary, skin infection or pipe swabs positive for USA300. Colonized participants had one or more nasal, axillary or pipe swab positive for USA300; infected participants had one or more skin infection swab positive for USA300.nnnRESULTSnThe prevalence of USA300 colonization or infection among 271 participants was 5.5% (range 3.1% to 9.0%). USA300 cases were more likely to report manipulation of skin infections (OR 9.55; 95% CI 2.74 to 33.26); use of crack pipes was not significant despite identification of the USA300 strain on two of four crack pipes tested. USA300 cases were more likely to report drug use between sex trade workers and clients (OR 5.86; 95% CI 1.63 to 21.00), and with casual sex partners (OR 5.40; 95% CI 1.64 to 17.78).nnnCONCLUSIONnOngoing efforts to promote the appropriate treatment of skin infections in this population are warranted. The association of USA300 colonization or infection and drug use with sexual partners suggest a role for sexual transmission of the USA300 strain of MRSA.

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.

Pilot testing of an out-of-country medical care questionnaire with screening and cost analysis of preemptive isolation for carbapenem-resistant Enterobacteriaceae in a large Canadian health region.

Nipunie Rajapakse1, Joseph Vayalumkal1,2, Debbie Lam-Li2, Craig Pearce2, Gwynne Rees2, Linda Kamhuka2, Gisele Peirano3, Corrinne Pidhorney2, Donna Ledgerwood2, Nancy Alfieri2, Karen Hope2, Dan Gregson3,4, Johann Pitout3, Thomas Louie 2,4, John Conly2,3,4 1Department of Pediatrics, Alberta Children’s Hospital, Calgary, Alberta, Canada 2Infec=on Preven=on and Control, Alberta Health Services – Calgary Zone, Calgary, Alberta, Canada 3Calgary Lab Services, Calgary, Alberta, Canada 4Department of Medicine, University of Calgary, Calgary, Alberta, Canada

Point prevalence study of antibiotic susceptibility of genital group B streptococcus isolated from near-term pregnant women in Calgary, Alberta

BACKGROUNDnGenital group B streptococcus (GBS) may be transmitted from a colonized mother to her infant if appropriate intrapartum antibiotic prophylaxis is not given. A recent case of GBS neonatal sepsis occurred due to an erythromycin-intermediate strain after empirical use of this drug as intrapartum prophylaxis.nnnOBJECTIVEnTo determine the regional antibiotic resistance rates of genital GBS isolates to penicillin, erythromycin and clindamycin.nnnMETHODSnA total of 309 genital GBS strains cultured from vaginal/rectal swabs were prospectively isolated and randomly selected between March and May 2011. Etest strips (bioMèrieux, France) were used to determine the minimum inhibitory concentrations to penicillin, erythromycin and clindamycin according to standard methods. All isolates that either demonstrated intermediate or full resistance to erythromycin had a D-test performed to detect inducible resistance to clindamycin. The resistance mechanism for each isolate was inferred from its antibiogram phenotype.nnnRESULTSnAll genital GBS isolates were susceptible to penicillin, but high rates of resistance were found to both erythromycin (25%) and clindamycin (22%), mainly due to acquisition of erythromycin ribosomal methylation genes (erm) that result in the MLSB resistance phenotype. Most often the MLSB resistance phenotype was constitutive (MLSB-C; 14.2%) rather than inducible (MLSB-I; 8.1%), and an efflux mechanism (msrA; 3%) was much less common.nnnDISCUSSIONnThe present article is the first point prevalence study of genital GBS antibiogram profile that has been reported from a Canadian health care region. The high rates of resistance of genital GBS to both erythromycin and clindamycin is mainly due to the acquisition and spread of erm genes conveying the MSLB phenotype.nnnCONCLUSIONnChanges to clinical and laboratory practice in the Calgary, Alberta, region were made to prevent additional cases of neonatal GBS sepsis due to inappropriate intrapartum antibiotic prescription.

Community-associated methicillin-resistant Staphylococcus aureus necrotizing pneumonia without evidence of antecedent viral upper respiratory infection.

Pneumonia caused by community-associated methicillin-resistant Staphylococcus aureus is frequently complicated and severe, with a high mortality rate. This case series describes a group of patients with necrotizing pneumonia caused by community-associated methicillin-resistant Staphylococcus aureus who were treated at three hospitals in Calgary, Alberta. Laboratory results and clinical outcomes are described.

Lyme disease: How reliable are serologic results?

See also page [1222][1] and [www.cmaj.ca/lookup/doi/10.1503/cmaj.141413][2]nnLyme disease is a tick-transmitted bacterial infection that is well established in North America. It is uncommon in most areas of Canada, but its incidence and geographic range are increasing. The accurate diagnosis of Lyme