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

• Published in: PloS one 2011-12, Vol.6 (12), p.e28547-e28547
• Main Authors: Vanderkooi, Otto G, Church, Deirdre L, MacDonald, Judy, Zucol, Franziska, Kellner, James D
• Format: Article
• Language: English
• Subjects: Alberta - epidemiology; Asthma; Biology; Blood; Children & youth; Communities; Disease Outbreaks; Disease susceptibility; Drug abuse; Drug Combinations; Drug dosages; Drugs; Epidemiology; Health aspects; Health services; Health surveillance; Homeless people; Homeless persons; Homelessness; Hospitals; Humans; Immunization; Institutions; Laboratories; Medicine; Microbial Sensitivity Tests; Older people; Outbreaks; Patients; Pneumococcal Infections - drug therapy; Pneumococcal Infections - epidemiology; Pneumococcal Infections - microbiology; Pneumonia; Population; Public health; Risk factors; Sepsis; Serotypes; Streptococcus infections; Streptococcus pneumoniae; Streptococcus pneumoniae - classification; Streptococcus pneumoniae - drug effects; Streptococcus pneumoniae - isolation & purification; Streptococcus pneumoniae - pathogenicity; Sulfadoxine; Surveillance; Trimethoprim; Vaccines
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0028547

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. 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). 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.