O: Public Health
Oral Abstract Submission
Background : Older adults residing in nursing homes (NH) are at increased risk for invasive group A Streptococcus (GAS) infections due to advanced age, presence of wounds, and comorbidities; approximately one third of infected patients die. Beginning in 2015, increasing numbers of GAS infections in NH residents and several NH clusters were reported from the Denver metropolitan area. Colorado Department of Public Health & Environment (CDPHE) and CDC investigated to characterize cases and assess if outbreaks resulted from interfacility transmission.
Methods : We reviewed data from Active Bacterial Core surveillance (ABCs) in the 5-county Denver area from January 2017–June 2018. We defined a case as isolation of GAS from a normally sterile site in a NH resident. GAS isolates underwent whole-genome sequencing (WGS) at CDC’s Streptococcus Laboratory to determine emm types for genotyping. Among isolates with the same emm type, pairwise single nucleotide polymorphism (SNP) distances were calculated using Nucmer software. In October 2018, a CDPHE-CDC team assessed infection control at NHs with cases of the most common emm type.
Results : Over 18 months, among > 100 NHs in the Denver area, ≥ 1 GAS case was identified in 29 NHs, with 6 having ≥ 3 cases. During this period, 68 cases in NH residents were identified. WGS identified 17 emm types among isolates from these cases; most common was emm11.10 (34%, n=22), a rare subtype in ABCs. All emm11.10 isolates had nearly identical genomes (average pairwise SNP distance: 3.2), and were isolated from 10 NHs, with 2 NHs having ≥ 4 cases. Multiple infection control lapses were noted during site visits to 8 NHs.
Multiple outbreaks due to GAS were noted in 5-county Denver area NHs in 2017–2018. WGS of surveillance isolates identified a rarely seen emm subtype 11.10 from multiple facilities with temporal and genomic clustering suggesting interfacility GAS transmission.