Abstract
BackgroundOutbreaks 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 FindingsCASPER (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/SignificanceDuring 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.
Highlights
Streptococcus pneumoniae is a leading cause of morbidity and mortality worldwide
We describe two large outbreaks of invasive pneumococcal disease (IPD) in Calgary, Alberta, caused by serotypes 5 and 8
Outbreak investigation Active, population-based surveillance of IPD has been conducted in the city of Calgary and surrounding area since January 1, 1998 by the Calgary Area Streptococcus pneumoniae Epidemiology Research (CASPER) team [14]
Summary
Streptococcus pneumoniae (pneumococcus) is a leading cause of morbidity and mortality worldwide. Bacteremia, meningitis and pneumonia are the most common manifestations of invasive pneumococcal disease (IPD). Some pneumococcal serotypes are more frequently associated with outbreaks, including serotypes 1, 2, 4, 5, 9V, 12F, 14 and 23F [8]. We describe two large outbreaks of IPD in Calgary, Alberta, caused by serotypes 5 and 8 These outbreaks took place in the community, but preferentially affected specific populations. The early features of these outbreaks were previously reported [9,10]. The ST5 outbreak spread across western Canada and some features have been reported elsewhere [11,12,13]. 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
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