Adhesion and internalization of group A streptococcus isolates found in Hawaii

Abstract

M/emm typing was performed for clinical isolates of GAS from Hawaiʻi. Of the 54 M/emm types found, 41% belonged to recently validated or newer sequence types. M/emm 4, 12, 28 and 1 were most frequently found throat associated. M/emm 85 and 63 were found frequently skin associated and emm 66 and 81 were more frequently associated with invasive disease. When tested for adherence, isolates from the skin, throat or invasive disease did not adhere differently to Hep-2 or HaCaT cell lines. When comparing isolates from invasive and noninvasive disease, no statistically significant difference was found. The degree of adherence among the isolates did not correlate with presence or absence of fibronectin binding protein genes or opacity factor production. Isolates 322 and 328 were recovered from the same nine-year old male subject. Isolate 322 was obtained when he had pharyngitis whereas isolate 328 was cultured from his blood four days later. Both isolates shared a number of identical characteristics. Both isolates sequenced as emm 81 and the sequence of the hypervariable region showed 100% identity. They shared the same T pattern, possessed the same pulsed-field gel electrophoresis, biochemical and fibronectin binding protein genetic profiles. Both were opacity factor positive. Despite these similarities, marked phenotypic differences were noted. When grown to stationary phase, isolate 328 was more adherent to Hep-2 and HaCaT cells than isolate 322; in Hep-2 cells, isolate 328 was internalized better than isolate 322. Isolate 322 displayed a more mucoidal appearance, produced a clearer zone of hemolysis and in broth, grew faster and to a higher absorbance with a less turbid broth appearance compared to 328. Differences in fibronectin binding as measured by enzyme-linked assays were found between the exponential and stationary growth phases of the isolates. The most remarkable difference was that isoiate 328 completely lacked speB activity compared to isolate 322 whose speB activity peaked during late exponential growth and continued throughout the stationary phase. The data support the idea that isolate 322 are 328 are closely related and the multiple phenotypic differences might be explained by a change in some, as yet, unidentified regulatory component.