High-Resolution Genotyping Elucidates the Epidemiology of Group A Streptococcus Outbreaks

Abstract

Streptococcus pyogenes strains were genotyped by a combination of molecular methods for high- resolution epidemiologic studies of disease outbreaks. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the emm gene is reported. Alone or in conjunction with other molecular techniques (16S ribotyping, pulsed-field gel electrophoresis, and detection of exotoxin genes), PCR-RFLP could differentiate outbreak-related strains from contemporaneous background strains of the same M serotype. Three outbreaks were studied: pharyngitis in a boarding school (serotype M5), cross-infection in a hospital burn unit (serotype M76), and severe invasive disease in two elderly care homes (serotype R28). It was possible, for example, to identify within serotype R28 a clone with particular potential for invasive disease. In all cases, the four molecular methods yielded complementary results that were hierarchically related. Strains could be assigned to the outbreak or the background in a precise, reproducible, and rapid manner.

Integration of Genomic and Other Epidemiologic Data to Investigate and Control a Cross-Institutional Outbreak ofStreptococcus pyogenes

“…Loss of pay when excluded from work in 1 setting may also contribute to spread of infection to other settings, unless staff members understand that this exclusion applies to similar work in other settings and comply with the exclusion from work in all settings. We found 1 other report of an iGAS outbreak across 2 LTCFs; the article explored the use of subtyping but did not include epidemiologic details of the outbreak (35). Spread of infection between institutions, resulting in apparently sporadic cases or small outbreaks in each, may be difficult to identify as a single outbreak.…”

Streptococcal emm types associated with T-agglutination types and the use of conserved emm gene restriction fragment patterns for subtyping group A streptococci

“…Furthermore, outbreak-related strains could be distinguished from other strains within the same M-type by the use of characteristic HaeIII profiles [16]. We have also found this strategy useful for this purpose (unpublished data); however, the combination of HaeIII and Hinc I1 often provides more discriminatory electrophoretic profiles than that of HaeIII alone.…”

Bacterial Phenotype Variants in Group B Streptococcal Toxic Shock Syndrome1

“…Antimicrobial susceptibility and MICs were determined by the Kirby-Bauer disk diffusion method and by Etest (AB Biodisk, Solna, Sweden), respectively. GBS isolates were subjected to pulsed-fi eld gel electrophoresis (PFGE) by using the restriction enzymes SmaI or XmaI (New England Biolabs, Ipswich, MA, USA) or ApaI (Promega, Madison, WI, USA), as described (17).…”