table 1. Continued Phase 1 (June 2–11) Pre-WGS
If WGS shows genetically linked S. pyogenes cases: - Hospital-wide antibiotics treatment will be considered to break the chain of transmissions. - Resources will be redeployed to focus more on institution-wide interventions rather than ward-level measures.
If WGS showed multiple clusters with or without interward genetic linkage. - Environmental hygiene will be further strengthened. - Investigation will be conducted to identify the role of the environment as a potential transmission route.
Phase 3 (September 5–November 11)
Strains sent for WGS: October 19, 2016 WGS results: October 27, 2016
Summary 1. Cases of S. pyogenes were identified in wards A, C, G, and H. 2. A general decreasing trend of patients involved in cluster 1 was noted (Figure 3) 3. By the end of October, the number of patients with skin lesions in ward A decreased from >80% to <10%. Pre-WGS Hypotheses and Planning Parameters 1. Isolates from wards A andC are likely to be related to cluster 1. 2. Isolates from G and H are likely to be genetically diverse (as seen before)
WGS Results 1. All isolates from wards A and C were genetically linked to cluster 1. 2. Isolates from wardsGandHwere genetically distinct to those from cluster 1 (Figure 1). Post-WGS Conclusions and Recommendations by the Outbreak Control Team 1. The committee recommended continuing the high level of environmental hygiene. 2. Surveillance for skin lesions in all wards in the institution is to be continued. 3. Sporadic cases of S. pyogenes are highly possible in the future; however, nosocomial transmission can and should be prevented. 4. To continue genomic surveillance for all S. pyogenes isolates from the institution until December 2016.
1. No further cases of genetically linked S. pyogenes transmission were identified in Wards A and C after October 2016.
Post-WGS
4. Environmental swabbing for S. pyogenes was considered but not done due to limitation in resources and logistical constraints. 5. An enhanced environmental cleaning protocol coupled with dermal decolonization of all patients in ward A for 5 days was implemented (Supplementary Figure1).
Remarks
NOTE. SNP, single-nucleotide polymorphism. aInfection control recommendations by the outbreak control team differed depending on the stage of the outbreak, number of affected patients, and WGS results. Patients underwent screening for
asymptomatic throat carriage, treatment for skin infections, eradication of throat carriage (if present), 5 days decolonization with chlorhexidine wipes, and measures to enhance personal hygiene. Staff members underwent screening for asymptomatic throat carriage, reinforcement of hand hygiene compliance, and education regarding S. pyogenes. Environmental hygiene was reinforced with terminal steam cleaning of the affected wards, and movement of patients, staff, and visitors was restricted. Visitors and volunteers who had entered the affected ward in the preceding 1 month were screened for asymptomatic throat carriage (Supplementary Table 1 and Figure 1).
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