Evading Detection and Antibiotics: Internalization Rates of Different Strains of Group A Streptococcus

Abstract

Objectives: (1) Determine the internalization rates of different strains of Group A Streptococcus (GAS). (2) Determine whether statistically different internalization rates occur in patients who receive a tonsillectomy for sleep-disordered breathing/sleep apnea versus chronic/recurrent tonsillitis. (3) Facilitate the development of GAS vaccine Methods: In vitro microbiology/tissue culture study at an academic tertiary referral center. All tonsillectomy specimens (performed for sleep disordered breathing spectrum and recurrent/chronic tonsillitis spectrum) were collected at the authors’ institution from September 2013 to November 2013. Each specimen was swabbed and bacteria cultured and emm typed. Only specimens with GAS were included in the study. The strains were grown in brain heart infusion (BHI) media to an optic density at 600 nm of 0.5. HeLa and nasopharyngeal carcinoma Detroit 562 cells were grown in tissue culture and subsequently infected with individual strains of GAS at a multiplicity of infection (MOI) of 1:10 for 2 hours. Cells were then washed with Dulbecco’s Modified Eagle Media (DMEM) and reincubated with DMEM plus gentamycin. The cells were then lysed, serial dilutions performed, and the lysate plated. Bacteria were counted and percent internalizations were calculated. This was repeated in triplicate for each strain. Results: Out of 396 eligible patients, 66 strains of GAS have been isolated. Both the Detroit and HeLa cells have been successfully grown in BHI. The bacterial strains have been subcultured. The authors plan on infecting the cells in March 2014 and will have have conclusive results by April 2014. Conclusions: None provided.