Judy MacDonald

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.

Changing Epidemiology of Invasive Pneumococcal Disease in Canada, 1998–2007: Update from the Calgary-Area Streptococcus pneumoniae Research (CASPER) Study

BACKGROUND Routine infant vaccination with 7-valent pneumococcal conjugate vaccine (PCV7) began in the Calgary Health Region (Alberta, Canada) in 2002. We measured the impact of this vaccine program on invasive pneumococcal disease (IPD). METHODS Prospective, population-based surveillance of all cases of IPD (with culture specimens obtained from sterile sites) was conducted from January 1998 through December 2007. Demographic and clinical data were collected. All viable isolates were saved and serotyped. RESULTS There were 1182 IPD cases over the 10-year period. Comparison of the vaccine period (2003-2007) with the prevaccine period (1998-2001) revealed that the incidence of IPD due to PCV7 serotypes decreased significantly by 86%, 59%, 38%, and 78% in the 6-23-month, 2-4-year, 16-64-year, and 65-84-year age groups, respectively. The total number of IPD cases decreased by 77%, 45%, and 34% in the 6-23-month, 2-4-year, and 65-84-year age groups, respectively. The incidence of IPD due to non-PCV7 serotypes increased by 183%, and the total incidence of IPD increased by 73% among adults aged 16-64 years; however, this increase was primarily attributed to a large outbreak of serotype 5 IPD among homeless adults during the period 2005-2007. There were 5 cases of IPD due to PCV7 serotypes among vaccinated children in the vaccine period. CONCLUSIONS Since the introduction of PCV7 vaccine, there has been a profound decrease in the total number of cases of IPD among children and in cases due to PCV7 serotypes among subjects of all ages in Calgary, indicating a strong direct effect and herd effect of the vaccine. The serotypes that now cause IPD have changed significantly. The magnitude and impact of replacement IPD caused by non-PCV7 serotypes is not yet known.

First Case of Zika Virus Infection in a Returning Canadian Traveler

A woman who recently traveled to Thailand came to a local emergency department with a fever and papular rash. She was tested for measles, malaria, and dengue. Positive finding for IgM antibody against dengue and a failure to seroconvert for IgG against dengue for multiple blood samples suggested an alternate flavivirus etiology. Amplification of a conserved region of the non-structural protein 5 gene of the genus Flavivirus yielded a polymerase chain reaction product with a matching sequence of 99% identity with Zika virus. A urine sample and a nasopharygeal swab specimen obtained for the measles investigation were also positive for this virus by reverse transcription polymerase chain reaction. Subsequently, the urine sample yielded a Zika virus isolate in cell culture. This case report describes a number of novel clinical and laboratory findings, the first documentation of this virus in Canada, and the second documentation from this region in Thailand.

Progress in the prevention of pneumococcal infection

Streptococcus pneumoniae (pneumococcus) remains an important human pathogen more than a century after its discovery, with infections occurring most commonly among young children and elderly people. It causes a wide range of invasive infections in normally sterile body sites such as blood and

Effects of Routine Infant Vaccination With the 7-Valent Pneumococcal Conjugate Vaccine on Nasopharyngeal Colonization With Streptococcus pneumoniae in Children in Calgary, Canada

Background: All Streptococcus pneumoniae disease is preceded by nasopharyngeal (NP) colonization. We studied the impact of 7-valent pneumococcal conjugate vaccine (PCV7) on colonization in healthy children. Methods: Routine PCV7 vaccination began in Alberta in 2002. Six point prevalence surveys were conducted from 2003 to 2005, in 7 community health centers in Calgary where children had their routine vaccinations. A questionnaire was administered and a single NP swab was obtained for culture. Serotyping was performed on all S. pneumoniae isolates. Results: There were 3398 children with complete data, 1307, 1225, and 866 in 12-month, 18-month, and 4–6 year groups, respectively. None had received PCV7 in survey 1. From survey 2 onwards, 92–98% of 12-month-olds had 3 or more doses of PCV7, and from survey 3 onwards, 95–99% of 18-month-olds had 3 or more doses. By survey 6, only 4% of 4–6 year olds had 3 or more doses. The overall S. pneumoniae colonization rate was 20%. In all age groups, including unvaccinated 4–6 year olds, there were significant declines in PCV7 serotypes, and increases in non-PCV7 serotypes. The largest increases were serotypes 6A, 15C, and 11A. Multivariate analysis found that factors including age, siblings, daycare attendance, episodes of otitis media, and antibiotic use affected S. pneumoniae colonization but only PCV7 vaccination was associated with decreased PCV7 serotype colonization and increased non-PCV7 colonization. Conclusions: Routine PCV7 vaccination has led to significant changes in the predominant S. pneumoniae serotypes found in NP colonization in both vaccinated and unvaccinated children, indicating both a direct and herd effect.

Case report: probable transmission of vaccine strain of yellow fever virus to an infant via breast milk

The 17D yellow fever vaccine is a live-virus vaccine that has been in use since the 1940s. The incidence of encephalitis after yellow fever vaccination among young infants is much higher than among children older than nine months of age. Until recently, avoidance of vaccination by breastfeeding women who have received yellow fever vaccine had been based on theoretical grounds only. We report the probable transmission of vaccine strain of yellow fever virus from a mother to her infant through breastfeeding.

Eradication of invasive pneumococcal disease due to the seven-valent pneumococcal conjugate vaccine serotypes in Calgary, Alberta.

Background: The seven-valent pneumococcal conjugate vaccine (PCV7) was licensed in Canada in 2001. Routine infant vaccination programs in Alberta began in 2002. Several years after PCV7 introduction, the routine use of PCV7 in infants and high-risk children has led to near elimination of invasive pneumococcal disease (IPD) caused by vaccine serotypes. Methods: Prospective, population-based surveillance of all IPD cases was conducted from January 1998 to December 2010. Demographic, clinical and microbiologic data were collected. Results: There were 1462 IPD cases over 13 years. Comparing PCV7 serotype IPD incidence in the prevaccine period (1998–2001) to the late postvaccine period (2007–2010), there were declines in children 0–5 months (100%), 6–23 months (98%), 2–4 years (97%), 5–15 years (100%) as well as in adults 16–64 years (73%), 65–84 years (90%) and ≥85 years of age (100%). From 2008 to 2010, there were no cases of PCV7 serotype IPD in children under 2 years of age. There have been increases in non-PCV7 serotype IPD; notably, serotypes 5 and 19A have increased significantly in adults and 19A in children. Conclusions: PCV7 serotype IPD has been eliminated in vaccine-eligible young children and nearly eliminated in all other age groups. Serotype 19A increased significantly at all ages before the introduction of an expanded valency pneumococcal conjugate vaccine.

Community-based outbreaks in vulnerable populations of invasive infections caused by Streptococcus pneumoniae serotypes 5 and 8 in Calgary, Canada.

Background Outbreaks of invasive pneumococcal disease (IPD) typically occur within institutions. Beginning in 2005, we detected an increase in serotype (ST) 5 and ST8 IPD cases, predominantly in homeless persons living in an open community. Methodology/Principal Findings CASPER (Calgary Area S. pneumoniae Epidemiology Research) surveillance study of all IPD (sterile site isolates) in our region (pop ∼1,100,000). Interviews and chart reviews of all cases and all isolates phenotypically analyzed and selected isolated tested by multi-locus sequence typing (MLST). Conclusions/Significance During 2005–2007, 162 cases of ST5 IPD and 45 cases of ST8 IPD were identified. The isolates demonstrated phenotypic and genotypic clonality. The ST5 isolates were sequence type (ST) 289 and demonstrated intermediate susceptibility to TMP-SMX. The ST8 isolates were predominantly ST1268, with a susceptible antimicrobial susceptibility profile. Individuals with ST5 IPD were more likely to be middle aged (OR 2.6), homeless (OR 4.4), using illicit drugs(OR 4.8), and asthmatic(OR 2.6). Those with ST8 were more likely to be male (OR 4.4), homeless (OR 2.6), aboriginal (OR7.3), and a current smoker (OR 2.5). Overlapping outbreaks of ST5 and ST8 IPD occurred in an open community in Calgary, Canada and homelessness was a predominant risk factor. Homelessness represents a unique community in which pneumococcal outbreaks can occur.

Trends in asymptomatic nasopharyngeal colonization with streptococcus pneumoniae after introduction of the 13-valent pneumococcal conjugate vaccine in Calgary, Canada.

Background: We previously reported serotype-specific trends in pneumococcal nasopharyngeal colonization soon after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in mid-2002. Our current aim is to describe later trends after PCV7 and early trends after PCV13 vaccine introduction in 2010. Methods: The Calgary Area Streptococcus pneumoniae Epidemiology Research team conducted 10 point-prevalence surveys of pneumococcal nasopharyngeal colonization in healthy children aged 12 and 18 months and 4.5 years biannually from 2003 to 2005 (previously reported) and annually in 2006, 2010, 2011 and 2012. Results: For surveys conducted during 2010–2012, the proportion colonized was 13.2% compared with 19.9% in surveys conducted during 2003–2006 (P < 0.001). Vaccination with 2 or more doses of PCV7 or PCV13, older age and recent antibiotic use reduced the odds of colonization with any pneumococcus. By 2012, 94% of all isolates were nonvaccine serotypes with 11A, 15A/B/C, 22F, 23A/B and 35B/F representing 75% of all isolates. Conclusions: Pneumococcal nasopharyngeal colonization has changed profoundly since the introduction of conjugate vaccines and overall colonization by pneumococcus has declined in recent years. By 2012, nonvaccine serotypes have nearly completely replaced vaccine serotypes. The impact on clinical disease remains to be seen.

Outbreak of Escherichia coli O157:H7 Infections Associated with Consumption of Beef Donair

The Calgary Health Region identified an outbreak of Escherichia coli 0157:H7 infection in September 2004 following a fourfold increase in laboratory reports. Clinical isolates were indistinguishable by pulsed-field gel electrophoresis (PFGE), and the PFGE pattern was unique in North America. Most affected individuals reported beef donair consumption in 10-day food histories. We conducted a matched case-control study, inspected the implicated food premises, and conducted a traceback investigation of suspect ground beef to determine the source of the outbreak and implement prevention and control measures. A total of 43 laboratory-confirmed cases were identified, with symptom onsets between 8 September and 1 October 2004. Among 26 matched case-control pairs, consumption of beef donair from one of two locations of a local restaurant chain was the only statistically significant risk factor for infection (matched odds ratio undefined; P < 0.01). No samples of the implicated ground beef were available for microbiological testing. We identified several opportunities for time-temperature abuse and other factors that may have contributed to the serving of unsafe donair meat at the implicated restaurants. This outbreak highlighted gaps in food safety policy related to beef donair and similar products in Canada. Immediately following the outbreak, the Region implemented new safe food handling requirements and a Federal/Provincial/Territorial Working Group was established to make recommendations for national food safety policies specific to these products.