Evaluation of a rapid diagnostic test for the detection of Streptococcus pyogenes in invasive infections

Invasive Streptococcus pyogenes diseases represent the most severe form of infection produced by this microorganism. Early diagnosis and treatment are important, due to its potential severity. Etiological confirmation of invasive infection is performed by culture, which takes between 18 and 48h. We tested a rapid immunochromatographic assay directly from clinical samples from normally sterile sites and positive blood culture bottles when positive cocci chains were observed by Gram staining. Eighty samples were analyzed. The rapid test was positive in 35 samples: in 34 of them S. pyogenes was confirmed by culture. The immunochromatographic method showed 97.1% sensitivity and 97.8% specificity. The strept A® immunochromatographic rapid test allows to obtain reliable results in less than 10min and is accessible to any microbiology laboratory. This study demonstrates the potential use of a rapid immunochromatographic method directly from clinical samples and positive blood cultures.