Lab Matters Winter 2025 | Page 23

INFECTIOUS DISEASES

By Elizabeth Toure, MPH, senior specialist, Infectious Diseases

When a cluster of invasive Group A Streptococcus( iGAS) cases appeared in a Colorado long-term care facility, the Colorado Department of Public Health and Environment( CDPHE) faced a crucial question: were these infections spreading from within the facility, or were they being introduced from the community? In the past, answering that question meant shipping samples to the US Centers for Disease Control and Prevention( CDC) and waiting for results. Now, with newly implemented GAS characterization capabilities in-house, including polymerase chain reaction( PCR) emm typing and whole genome sequencing( WGS), CDPHE could act rapidly and efficiently. Using their high-throughput Standard BioTools Biomark X9™ platform to run CDC’ s emm typing assay, the team generated same-day results that ultimately revealed the outbreak was likely driven by intra-facility spread. This critical information allowed public health officials to quickly zero in on infection prevention and control measures at the facility— demonstrating how local genomic capacity can accelerate outbreak response.

While GAS typically causes mild infections, such as strep throat, in rare cases, it can become invasive leading to severe and potentially life-threatening illness. Because iGAS can spread rapidly in healthcare and communal settings, timely and accurate laboratory testing is essential to detect outbreaks early, guide public health response and prevent further transmission. Characterization of GAS isolates, particularly emm typing using PCR or WGS, is necessary for quickly identifying whether cases are linked. Emm typing can rule out a single strain outbreak and support the initial investigation, while WGS can elucidate

CDPHE’ s Kevin Castro Vital prepares to run CDC’ s Group A Strep emm typing assay on the high-throughput Standard Biotools X9 TM platform. Photo: Colorado Department of Public Health and Environment.

transmission patterns within and between healthcare facilities. For CDPHE, implementing these methods has been an important step in strengthening genomic epidemiology, especially as iGAS cases have been increasing in Colorado since 2022.

Colorado’ s new capability was made possible through Advanced Molecular Detection( AMD) funding from CDC, which has been instrumental in expanding sequencing capacity in public health laboratories nationwide. With support from APHL in collaboration with CDC’ s Division of Bacterial Diseases, AMD funds enabled CDPHE— along with two other public health laboratories— to strengthen their GAS testing by enhancing PCR and WGS capabilities.

On the other side of the country, the South Carolina Department of Public

Health( SCDPH) used the AMD funding to successfully validate WGS emm typing, representing their first-ever bioinformatics validation.

“ This was a landmark accomplishment for the molecular genomics program and has provided critical support for outbreak investigations across the state,” said Cory Weaver, PhD, section director of Virology, Serology and Molecular at the SCDPH. Next door, the North Carolina State Laboratory of Public Health( NCSLPH) piloted a feasibility project of GAS sequencing for epidemiological investigations using AMD funding.

“ We were able to successfully complete a WGS evaluation study for emm typing and multi-locus sequence type( MLST) utilizing a panel of diverse, banked isolates with 100 % accuracy and precision when compared to sequencing results from the CDC Streptococcus group,” noted William Glover, PhD, D( ABMM), MT( ASCP), NCSLPH assistant director of Infectious Diseases.“ This project allowed us to demonstrate that the NCSLPH Sequencing and Bioinformatics Response Unit is prepared to respond to future GAS outbreaks in the state.”

The success of these laboratories’ expansion of GAS characterization demonstrates the value of federal support to advance AMD capabilities. Faster, more precise data help epidemiologists detect transmission, guide interventions and prevent further disease. These improvements not only strengthen the ability to rapidly respond to iGAS outbreaks, but also build broader infrastructure, technical expertise and capability for future assay implementation, enabling these laboratories to respond more efficiently to future emerging infectious threats. g