Mdp. Boyle et al., ROLE OF EMM AND MRP GENES IN THE VIRULENCE OF GROUP-A STREPTOCOCCAL ISOLATE-64 14 IN A MOUSE MODEL OF SKIN INFECTION/, The Journal of infectious diseases, 177(4), 1998, pp. 991-997
The virulence of group A streptococcal isolate 64/14 and paired isogen
ic mutants in which either the emm or mrp gene had been insertionally
inactivated was compared in mice. Loss of expression of the emm gene p
roduct resulted in a significant loss of virulence when the isolate wa
s injected into the skin but had no significant difference when inject
ed intraperitoneally. By contrast, inactivation of the mrp gene caused
the organism to be more virulent in the skin, while having no signifi
cant effect intraperitoneally. An isogenic mutant, in which the mga ge
ne was inactivated and neither the emm gene nor the mrp gene was expre
ssed, demonstrated no significant difference in virulence from the wil
d type organism. Organisms recovered from the spleen of mice lethally
infected with the mga mutant expressed all Mga-regulated IgG-binding g
ene products despite the presence of the spectinomycin-resistance cass
ette, which was used to inactivate the mga gene, in its original posit
ion.