VIRULENCE POTENTIAL OF BULGARIAN STREPTOCOCCUS PYOGENES CLINICAL ISOLATES

Streptococcus pyogenes (known as Lancefield Group A streptococcus or GAS) is an important gram-positive species responsible for various serious invasive or non-invasive human infections. The objective of this study was to determine the presence of genes encoding important factors of virulence in Bulgarian clinical GAS isolates and to analyze the results in terms of geographical distribution and areas of inflammation. Clinical GAS strains (n = 126) were screened for the presence of eighteen virulence genes using multiplex polymerase chain reaction (PCR). All of the tested strains were shown to carry the genes sdaB, speB, sypCEP; more than 80%, mac and smeZ; followed by sdc, speJ and speG (73.80%, 65.87% and 52.38%, resp.). The occurrence of virulence-associated genes in Bulgarian isolates was analyzed with regard to previous reports on GAS toxin genes in different countries and continents. An attempt was made to seek association between the detected GAS virulence genes and the areas of inflammation, and in respect to invasive and non-invasive isolates. To the best of our knowledge, this is the first study to show that about one third of Bulgarian GAS isolates have a very high pathogenic potential, with seventeen genes encoding important virulence factors present out of eighteen tested ones. The tested GAS strains demonstrated more virulent potential than the ones from some other countries. speA, speF, speL and speM were detected most often in invasive isolates (p < 0.05).